U.S. patent application number 10/245313 was filed with the patent office on 2004-01-29 for intelligent system for generating and executing a sheet metal bending plan.
This patent application is currently assigned to AMADA AMERICA, INC.. Invention is credited to Bourne, David Alan, Hazama, Kensuke, Kim, Kyoung Hung, Krishnan, Sivaraj Sivarama, Williams, Duane Thomas.
Application Number | 20040019402 10/245313 |
Document ID | / |
Family ID | 26991041 |
Filed Date | 2004-01-29 |
United States Patent
Application |
20040019402 |
Kind Code |
A1 |
Bourne, David Alan ; et
al. |
January 29, 2004 |
Intelligent system for generating and executing a sheet metal
bending plan
Abstract
An intelligent sheet metal bending system is disclosed, having a
cooperative generative planning system. A planning module interacts
with several expert modules to develop a bending plan. The planning
module utilizes a state-space search algorithm. Computerized
methods are provided for selecting a robot gripper and a repo
gripper, and for determining the optimal placement of such grippers
as they are holding a workpiece being formed by the bending
apparatus. Computerized methods are provided for selecting tooling
to be used by the bending apparatus, and for determining a tooling
stage layout. An operations planning method is provided which
allows the bending apparatus to be set up concurrently while
time-consuming calculations, such as motion planning, are
performed. An additional method or system is provided for
positioning tooling stages by using a backstage guide member which
guides placement of a tooling stage along the die rail of the
bending apparatus. A method is provided for learning motion control
offset values, and for eliminating the need for superfluous
sensor-based control operations once the motion control offset
values are known. The planning system may be used for facilitating
functions such as design and assembly system, which may perform
designing, costing, scheduling, and/or manufacture and
assembly.
Inventors: |
Bourne, David Alan;
(Pittsburgh, PA) ; Williams, Duane Thomas;
(Pittsburgh, PA) ; Kim, Kyoung Hung; (Pittsburgh,
PA) ; Krishnan, Sivaraj Sivarama; (Bangalore, IN)
; Hazama, Kensuke; (Buena Park, CA) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
AMADA AMERICA, INC.
Buena Park
CA
AMADA COMPANY, LTD.
Kanagawa
|
Family ID: |
26991041 |
Appl. No.: |
10/245313 |
Filed: |
September 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10245313 |
Sep 18, 2002 |
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09930252 |
Aug 16, 2001 |
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6507767 |
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09930252 |
Aug 16, 2001 |
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09207268 |
Dec 8, 1998 |
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6341243 |
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09207268 |
Dec 8, 1998 |
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08386369 |
Feb 9, 1995 |
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5969973 |
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08386369 |
Feb 9, 1995 |
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08338113 |
Nov 9, 1994 |
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Current U.S.
Class: |
700/165 |
Current CPC
Class: |
Y02P 90/02 20151101;
Y02P 90/86 20151101; G05B 2219/31352 20130101; Y02P 90/087
20151101; G05B 19/4069 20130101; G05B 19/41825 20130101; Y02P
90/265 20151101; G05B 19/4097 20130101; G05B 2219/45143 20130101;
B21D 5/02 20130101; Y02P 90/20 20151101; G05B 2219/35189 20130101;
G05B 2219/39467 20130101; G05B 2219/39105 20130101 |
Class at
Publication: |
700/165 |
International
Class: |
G06F 019/00 |
Claims
What is claimed is:
1. In a computer having at least one processor and a memory, a
device that selects a gripper that holds a workpiece to be utilized
by a bending apparatus that bends unfinished workpieces formed of
sheets of malleable material, the device comprising: a reader; a
former; a chooser; a predictor; a determiner; and an adjuster;
wherein said reader reads information describing geometry of a
library of grippers to be chosen from, said former forms a set of
available grippers excluding grippers that have certain undesired
geometric features, said chooser chooses a gripper from the set of
available grippers as a function of width of the gripper, length of
the gripper, and knuckle height of the gripper, said predictor is
adapted to predict, for each gripper within the set of available
grippers, a repo number equal to an estimated number of times the
bending apparatus will need to change the position at which the
gripper holds the workpiece in order to perform a complete sequence
of bending operations on the workpiece, said determiner is adapted
to determine the smallest predicted repo number, and said adjuster
is adapted to adjust the set of available grippers to include the
available grippers having a repo number equal to the smallest
predicted repo number, before choosing a gripper as a function of
the width, length and knuckle height of the gripper.
Description
1. RELATED APPLICATION DATA
[0001] This is a Continuation application of U.S. application Ser.
No. 09/930,252 filed Aug. 16, 2001, which was a Continuation of
U.S. application Ser. No. 09/207,268 filed Dec. 8, 1998, which was
a Continuation of U.S. patent application Ser. No. 08/386,369,
filed Feb. 9, 1995, which was a Continuation of U.S. application
Ser. No. 08/338,113, filed Nov. 9, 1994, the contents of which are
expressly incorporated by reference herein in their entireties. The
present disclosure is also related to the disclosure provided in
the following U.S. applications filed on even date herewith:
"Method for Planning/Controlling Robot Motion", U.S. patent
application Ser. No. 08/338,115, filed on Nov. 9, 1994; "Methods
for Backgaging and Sensor-Based Control of Bending Operations",
U.S. patent application Ser. No. 08/338,153, filed on Nov. 9, 1994;
and "Fingerpad Force Sensing System", U.S. patent application Ser.
No. 08/338,095, filed on Nov. 9, 1994; and the disclosures of all
of these applications are expressly incorporated by reference
herein in their entireties.
2. COMPUTER PROGRAM LISTING APPENDIX
[0002] This application includes a computer program listing
appendix for Appendices A-D. The computer program listing appendix
consists of one CD-ROM including 30 images.
3. COPYRIGHT NOTICE
[0003] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent disclosure, as it appears in the Patent and Trademark
Office patent files or records, but otherwise reserves all
copyright rights whatsoever.
BACKGROUND OF THE INVENTION
[0004] b 1. Field of the Invention
[0005] The present invention is directed to methods and subsystems
which may be provided in an intelligent bent sheet metal designing,
planning and manufacturing system and the like.
[0006] 2. Discussion of Background Information
[0007] FIGS. 1-3 illustrate, in a simplified view, an example
conventional bending workstation 10 for bending a sheet metal part
(workpiece) 16 under the control of a manually created program
downloaded to various control devices provided within the
workstation. The illustrated bending workstation 10 is a BM100
Amada workstation.
[0008] (a) The Hardware and its Operation
[0009] FIG. 1 shows an overall simplified view of bending
workstation 10. FIG. 2 shows a partial view of a press brake 29,
positioned to perform a bend an a workpiece 16. The elements shown
in FIG. 2 include a robot arm 12 having a robot arm gripper 14
grasping a workpiece 16, a punch 18 being held by a punch holder
20, and a die 19 which is placed on a die rail 22. A backgage
mechanism 24 is illustrated to the left of punch 18 and die 19.
[0010] As shown in FIG. 1, bending workstation 10 includes four
significant mechanical components a press brake 29 for bending
workpiece 16; a five degree-of-freedom (5 DOF) robotic manipulator
(robot) 12 for handling and positioning workpiece 16 within press
brake 29; a material loader/unloader (L/UL) 30 for loading and
positioning a blank workpiece at a location for, robot 12 to grab,
and for unloading finished workpieces; and a repositioning gripper
32 for holding workpiece 16 while robot 12 changes its grasp.
[0011] Press brake 29 includes several components as illustrated in
FIGS. 1-3. Viewing FIG. 3, press brake 29 includes at least one die
19 which is placed an a die rail 22, and at least one corresponding
punch tool 18 which is held by a punch tool holder 20. Press brake
29 further includes a backgage mechanism 24.
[0012] As shown in FIG. 2, robot arm 12 includes a robot arm
gripper 14 which is used to grasp workpiece 16. As shown in FIG. 1,
material leader/unloader 30 includes several suction cups 21 which
create an upwardly directed suction force for lifting a sheet metal
workpiece 16, thereby allowing L/UL 30 to pass workpiece 16 to
gripper 14 of robot 12, and to subsequently retrieve a finished
workpiece 16 from gripper 14 and unload the finished workpiece.
[0013] In operation, loader/unloader (L/UL) 30 will lift a blank
workpiece 16 from a receptacle (not shown), and will raise and move
workpiece 16 to a position to be grabbed by gripper 14 of robot 12.
Robot 12 then maneuvers itself to a position corresponding to a
particular bending stage located within bending workstation 10.
Referring to each of FIGS. 1 and 3, stage 1 comprises the stage at
the leftmost portion of press brake 29, and stage 2 is located to
the right of stage 1 along die rail 22.
[0014] If the first bend is to be made at stage 1, robot 12 will
move workpiece 16 to stage 1, and as shown in FIG. 2, will maneuver
workpiece 16 within press brake 29, at a location between punch
tool 13 and die 19, until it reaches and touches a backstop portion
of backgage mechanism 24. With the aid of backgage mechanism 24,
the position of workpiece 16 is adjusted by robot arm 12. Then, a
bend operation is performed an workpiece 16 at stage 1. In
performing the bend operation, die rail 22 moves upward (along a D
axis), as indicated by the directional arrow A in FIG. 2. As punch
tool 18 and die 19 simultaneously contact workpiece 16, so that
workpiece 16 assumes a relatively stable position within press
brake 29, gripper 14 will release its grasp on workpiece 16, and
robot 12 will move gripper 14 away from workpiece 16. Press brake
29 will then complete its bending of workpiece 16, by completing
the upward movement of die 19 until the proper bend has been
formed.
[0015] Once die 19 is engaged against punch tool 13, holding
workpiece 16 in its bent state, before disengaging die 19 by
lowering press brake 29, robot arm 12 will reposition its robot arm
gripper 14 to hold workpiece 16. Once gripper 14 is holding
workpiece 16, die 19 will be disengaged by releasing press brake
29. Robot 12 then maneuvers and repositions workpiece 16 in order
to perform the next bend in the particular bend sequence that has
been programmed for workpiece 16. The next bend within the bend
sequence may be performed either at the same stage, or at a
different stage, such as stage 2, depending upon the type of bends
to be performed, and the tooling provided within press brake
29.
[0016] Depending upon the next bend to be performed, and the
configuration of workpiece 16, the gripping position of gripper 14
may need to be repositioned. Repositioning gripper 32, shown in
FIG. 1, is provided for this purpose. Before performing the next
bend, for which repositioning of robot gripper 14 is needed,
workpiece 16 will be moved by robot 12 to repositioning gripper 32.
Repositioning gripper 32 will then grasp workpiece 16 so that robot
gripper 14 can regrip workpiece 16 at a location appropriate for
the next bend or sequence of bends.
[0017] (b) The Control System
[0018] The bending workstation 10 illustrated in FIG. 1 is
controlled by several control devices which are housed separately,
including an MM20-CAPS interface 40, a press brae controller 42, a
robot controller 44, and a lead/unload unit controller 46. Press
brake controller 42 comprises an NC9R press brake controller, and
robot controller 44 comprises a 25B robot controller, which are
each supplied by Amada. Each of press brake controller 42 and robot
controller 44 have their own CPU and programming environments
Load/unload unit controller 46 comprises a stand alone Programmable
Logic Controller (PLC), and is wired to respective consoles
provided for press brake controller 42 and robot controller 44.
[0019] Each of controllers 42, 44, and 46 has a different style
bus, architecture, and manufacturer. They are coordinated primarily
by parallel I/O signals. Serial interfaces are provided far
transporting bending and robot programs to the controllers, each of
which is programmed in a different manner. For example, logic
diagrams are used to program the PLC of the load/unload controller
46, and Re is used to program robot controller 44.
[0020] (c) The Design/Manufacture Process
[0021] The overall design/manufacture process for bending sheer
metal includes several steps. First, a part to be produced is
typically designed using an appropriate CAD system. Then, a plan is
generated which defines the tooling to be used and a sequence of
bends to be performed. Once the needed tooling is determined, an
operator will begin to set up the bending workstation. After the
workstation is set up, the plan is executed, i.e., a workpiece is
loaded and operation of the bending workstation is controlled to
execute the complete sequence of bends an a blank sheet metal
workpiece. The results of the initial runs of the bending
workstation are then fed back to the design step, where appropriate
modifications may be made in the design of the part in view of the
actual operation of the system.
[0022] In the planning step, a plan is developed for bending
workstation 10 in order to configure the system to perform a
sequence of bending operations. Needed hardware must be selected,
including appropriate dies, punch tools, grippers, and so on. In
addition, the bending sequence must be determined, which includes
the ordering and selection of bends to be performed by bending
workstation 10. In selecting the hardware, and in determining the
bending sequence, along with other parameters, software will be
generated to operate bending workstation 10, so that bending
workstation 10 can automatically perform various operations of the
bending process.
[0023] A plan for a BM100 bending workstation includes generated
software such as an NC9R press brake program and a 25B RML robot
program. Each of these programs may be created with the use of an
initial part design created from a CAD system. Both the robot
program and the bending program must be developed manually, and are
quite labor-intensive Previously developed program are classified
by the nether of bends and/or by the directions of the bends.
Engineers examine each part style to determine if previously
developed and classified programs may be used or whether a new
program must he written. However, since each classified program
typically supports only a narrow range of acceptable part
dimensions, new programs must frequently be written by the
engineers. The final RML robot program, when complete, is compiled
and downgraded by the MM20-CAS system 40 to robot controller 44.
The bending program is entered and debugged on a control pendant
provided on press brake controller 42. After entering the robot and
bending programs into the system, an operator performs several
manual operations to walk the system through the several operations
to be performed. For example, an operator will manually operate a
hand-held pendant of the robot controller to manually move the
robot to the loading and unloading positions, after which the
interface console 40 will store the appropriate locations into the
final RML program to be compiled and down-loaded to robot
controller 44. In addition, in producing the bending program, the
operator may control the system to follow the planned bend
sequence, in order to determine the values for the backgage
position (L axis) and the die rail position (D axis).
[0024] (d) Intelligent Manufacturing Workstations
[0025] Various proposals have been made in order to overcome many
of the drawbacks with prior systems such as the BM100 Amada bending
workstation, and research has been conducted in the area of
intelligent manufacturing workstations. Some proposed features of
intelligent sheet metal bending workstations included features such
as open architecture, including open system configurations and
distributed decision making, and enhanced computer aided design and
geometric modeling systems.
[0026] A paper entitled "Intelligent Manufacturing Workstations"
was presented at the 1992 A Winter Annual Meeting regarding
Knowledge-Based Automation of Processes an Nov. 13, 1992 by David
Alan Bourne; the content of the Paper is expressly incorporated
herein by reference in it entirety. In the Paper, an intelligent
manufacturing workstation is defined as a self-contained system
that takes a new design for a part and manufactures it
automatically. The process is stated to include automated setup,
part programming, control, and feedback to design.
[0027] The Paper discusses several components of an overall
intelligent manufacturing workstation, including features such as
open architecture, the use of software modules that communicate via
a query-based language, part design, operations planning,
workstation coal, and geometric modeling.
[0028] (1) Open Architecture
[0029] It has been recognized that an effective intelligent
manufacturing workstation should have open software, open
controller and open mechanism architecture. That is, a machine tool
user operating such a workstation should be able to add onto the
software, the controller, and the mechanism architectures of the
workstation in order to improve their functions.
[0030] (2) Soft-Ware Modules Using Query-Based Language
[0031] Software modules have been suggested, in the above-noted
paper by David Bourne, for use in an intelligent manufacturing
workstation. Such modules would be split along knowledge boundaries
which have been defined in industrial practice, including, e.g.,
tooling, operations, programming, planning and design. The software
modules would be responsible for understanding commands and data
specifications, and for answering questions in their own area of
specialty. A particular module might be configured to request
information from other modules so that it has adequate information
to solve its designated problems, to communicate in a standard
language, and to work on several problems at once. In addition,
each module would know which other module to ask far information
and provide assistance in formulating a question for the receiving
module. The general software architecture proposed in the
above-noted Paper is illustrated in FIG. 4. The proposed
architecture includes a designer 50, a bend sequence planner 52, a
module 54 for sequence planning, execution and error handling, a
modeler 56, a module 58 for sensor interpretation, and modules 60,
62 for process control and holding, and fixturing. Each of the
modules for sensor interpretation 58, process control 60, and
holding and fixturing 62 are coupled to external machine and sensor
drives 64. A control subsystem 68 is formed by several of the
modules, including sequence planning, execution and error handling
module 54, modeler 56, and the modules for sensor interpretation
58, process control 60 and holding and fixturing 62. Control
subsystem 68 is shown as being implemented within a Chimera
operating system. All of the modules may be connected to other
factory systems 66, including, e.g., systems for scheduling,
operations, and process planning.
[0032] (3) Design Tools
[0033] Experimentation has been conducted with design tools that
constantly manage the relationship between a stock part and a final
part as it is applied to sheet metal bending, as noted in the
above-referenced Paper, and as disclosed by C. Wang in "A Parallel
Designer for Sheet Metal Parts," Mechanical Engineering Master's
Report, Carnegie Mellon (1992), the content of which is expressly
incorporated herein by reference in its entirety. The design
information, which may be described in 3D, or as a 2D flat pattern,
is automatically maintained (in parallel) with another
representation of the developing part. In this way, a connection
between each of the features of the initial stock part and the
final part is maintained.
[0034] (4) The Planning System
[0035] Once the design is complete, a planner typically then
produces a plan which will later be used to execute the
manufacturing process. The plan includes several instructions
regarding the sequencing of machine operations to produce the
desired part. An optimal plan will result in a reduction of setup
time, a reduction in the existence of scrap after production of the
parts, an increase in part quality, and an increase in production
rate. To promulgate such advantages, the above-noted Paper
recommends that as much specific knowledge as possible be separated
from the planner so that the planner can be easily adapted to
different machines and processes. A "query-based" planning system
is thus proposed which shifts the emphasis of the planner to asking
expert questions, rather than attempting to act as a self-contained
expert.
[0036] (5) Workstation Control
[0037] The above-noted Paper proposes that the controller use an
off-the-shelf engineering UNIX workstation as the core computing
resource. The workstation may include in its back-plane an
extension rack of special-purpose boards and an additional CPU,
that runs with a real-time version of the UNIX operating system,
called CHIMERA-II. See, e.g., STEWART et al., Robotics Institute
Technical Report, entitled "CHIMERA II: A Real-Time UNIX-Compatible
Multiprocessor Operating System for Sensor Based Control
Applications;" Carnegie Mellon, CMU-RI-TR-89-24 (1989), the content
of which is expressly incorporated by reference herein in its
entirety.
[0038] (6) Geometric Modeling
[0039] Geometric modeling is an important component in intelligent
machining workstations. Several modelers have been experimented
with during a project in the Robotics Institute at Carnegie Mellon
University. A geometric modeler called "NOODLES" has been proposed
for use as a modeler in an intelligent manufacturing workstation.
The NOODLES modeler is discussed by GURSOZ et al., in "Boolean Set
operations on non-manifold boundary representation objects," in
Computer Aided Design, Butterworth-Heinenmann LTD., Vol. 23, No. 1,
January, 1991, the content of which expressly incorporated by
reference herein in its entirety. The NOODLES system makes far
fewer assumptions about what constitutes valid edge topologies, and
thus overcomes problems with other modeling systems, which would
enter into infinite loops when the edge topology of a geometric
model would violate system assumptions.
[0040] 6. Term Definitions
[0041] For purposes of clarification, and to assist readers in an
understanding of the present invention, the following terms and
acronyms used herein are defined.
[0042] bending apparatus/bending workstation--a workstation or
apparatus for performing modern sheet metal working functions;
including bend operations.
[0043] bending sheets of malleable material--working of sheets of
malleable material, such as sheet metal, including, and not limited
to, up-action air bending, V bending; R bending, hemming, seaming,
coining, bottoming, forming, wiping, folding type bending, custom
bending, and so on.
[0044] operations plan--a sequence of operations to be performed by
a part forming apparatus in order to form a finished part from a
piece of unfinished material. In the context of bend sequence
planning, an operations plan (bend sequence plan) comprises a
sequence of operations to be performed by a bending apparatus for
bending workpieces comprising sheets of malleable material, the
sequence of operations including a bend sequence which includes all
of the bends needed to form a finished-bent workpiece
[0045] subplan--a portion of a complete operations plan. In the
context of bend sequence planning, a subplan comprises a part of
the information needed to set up and/or control a bending
workstation/apparatus.
SUMMARY OF THE INVENTION
[0046] In view of the above, the present invention, through one or
more of its various aspects and/or embodiments, is thus presented
to bring about one or more objects and advantages, such as those
noted below.
[0047] Generally speaking, it is an object of the present invention
to provide an intelligent bending workstation environment/system
which may be easily upgraded and integrated with additional or
alternate hardware and software modules A further object is to
provide such a system which can he used to economically produce
very small batch sizes (of one or more workpieces) with high
quality, and in a short amount of time. In addition, an abject is
to provide such a system that is flexible and that is able to
accommodate new and different part styles in the design and
manufacture process. The system of the present invention is
intended to operate efficiently in large volume production, and to
learn from initial production runs in order to maximize
efficiency.
[0048] An additional object of the invention is to maintain quality
of the produced parts throughout the process, and to avoid errors
and collisions during execution of the process by the bending
workstation. It is a further abject of the present invention to
provide an intelligent sheet metal bending workstation which makes
small batches of sheet metal parts from CAD descriptions. In this
regard, a process planner is provided that selects the necessary
hardware (e.g., dies, punches, grippers, sensors) to be utilized by
the bending workstation, determines bending sequences, and
generates the necessary software to operate the bending
machine.
[0049] It is a further object of the present invention to provide
such an intelligent, automated bending workstation which first
generates a process plan and then executes the generated plan using
a real-time sensor-based control method. When the process is
executed, the results thereof may be recorded for later review, so
that the process may be refined to make it more efficient, and to
reduce the occurrence of errors during execution.
[0050] An additional object of the present invention is to provide
a system which can produce a plan for bending a sheet metal
workpiece, in which the smallest number of tooling stages will be
utilized to make the part A further object is to provide a system
that will efficiently and automatically produce the plan to be
utilized by the bending workstation, set up the workstation, and
execute the plan.
[0051] The present invention, therefore, is directed-to several
systems, methods and sub-components provided in connection with a
system for generating a plan which comprises a sequence of
operations to be performed by a bending apparatus for bending
workpieces comprising sheets of malleable material. The bending
apparatus has a gripper for gripping a workpiece while performing a
bend, and the sequence of operation includes a set of N bends for
forming a finished workpiece from a stock sheet of malleable
material. The system includes a proposing mechanism for proposing,
for an mth operation within the sequence of operations, a plurality
of proposed operations including a plurality of proposed bends to
be performed by the apparatus. In addition, the system includes a
subplan mechanism for providing a proposed subplan that accompanies
each proposed bend, and a generating mechanism for generating a
plan including a sequence of bends from a first bend through an Nth
bend, by choosing each bend in the sequence of operations based
upon the proposed bends and the proposed subplan that accompanies
each proposed bend.
[0052] The proposing mechanism may be designed so that it proposes
bends among the complete set of N bends that are still remaining,
or proposes bends among the complete set of bends that are still
remaining less bends blacked due to constraints. In addition, the
proposing mechanism may propose, for an mth operation, a
repositioning of a gripper's hold an the workpiece.
[0053] In accordance with a specific aspect of the invention, the
generated plan further includes at least part of the proposed
subplans that accompany the chosen bends. The system may further
include a mechanism for representing the mth operation as an mth
level of a search tree. The proposed subplans may include setup and
control information for the bending apparatus, and may further
comprise final locations on the workpiece at which the gripper will
grip the workpiece while performing the bends of the bend sequence.
The proposed subplans may further include ranges of locations on
the workpiece at which the gripper can grip the workpiece while
performing the bends of the bend sequence. In addition, the
proposed subplans may comprise: numbers representing a predicted
number of repositionings of the gripper needed to complete the
sequence of bends, indications that the next bend in the sequence
cannot be performed unless the gripper is first repositioned,
and/or locations on the workpiece at which a repositioning gripper
(i.e., a repo gripper) will grip the workpiece while performing a
repositioning operation. Additionally, the proposed subplans nay
include: tooling stages to be utilized to perform the bends in the
bend sequence, positions along a tooling stage at which the
workpiece will be loaded into the bending apparatus in order to
perform the bends, and/or motion plans for maneuvering around
tooling stages in performing the bends.
[0054] In accordance with a further aspect of the system, an
estimating device is provided for estimating a cost to be
associated with each proposed bend. In this regard, the generating
mechanism may generate a plan including a sequence of bends from a
first through an Nth bend, by choosing each bend in the sequence of
operations based upon the proposed bend, the proposed subplan that
accompanies each proposed bend, and the estimated costs associated
with each proposed bend. The estimated costs associated with an nth
bend in the sequence of N bends may comprise a k cost calculated
based upon an estimated amount of time it will take the bending
apparatus to complete one or more operations of the bend. The
estimated costs associated with an nth bend in a sequence of N
bends may comprise an h cost calculated based upon an estimated
total amount of time it will take the bending apparatus to complete
one or more operations of each of the rest of the bends in the bend
sequence that follow the nth bend.
[0055] The one or more operations of the bend which will be timed
in order to calculate the k and h costs may comprise moving the
workpiece from a tooling stage location of a preceding bend to a
tooling stage location of the given bend. The one or more
operations of a given bend may also comprise installing, when
setting up the bending apparatus, an additional tooling stage
needed to perform the given bend. The one or more operations of a
given bend may also comprise repositioning of the gripper's hold on
the workpiece before performing the given bend.
[0056] In accordance with a other aspect of the present invention,
the proposing mechanism and the generating mechanism collectively
comprise a bend sequence planning module, and the subplan mechanism
and the estimating mechanism collectively comprise a plurality of
expert modules. The expert modules may each operate the subplan
mechanism and the estimating mechanism when the proposing mechanism
proposes a proposed operation for performance as the mth operation
within the sequence of operations. The plurality of expert modules
may comprise a holding expert module which is capable of operating
the subplan mechanism to provide a proposed suplan, including
information regarding a location on the workpiece at which the
gripper can hold the workpiece while performing the bends of the
bend sequence. The plurality of expert modules may comprise a
holding expert module which is capable of operating the estimating
mechanism to estimate a holding cost, calculated based upon whether
a gripper's hold on the workpiece is to be repositioned before
performing a given bend. In addition, the plurality of expert
modules may comprise a tooling expert module which is capable of
operating the subplan mechanism to provide a proposed tooling
subplan that includes information regarding a position along a
tooling stage at which the workpiece will be loaded into the
bending apparatus in order to perform a given bend. The tooling
expert may also be capable of operating the estimating mechanism to
estimate a cost based upon an amount of time to install, when
setting up the bending apparatus, an additional tooling stage
needed to perform a given bend. The motion expert module may also
be capable of operating the estimating mechanism to estimate a cost
based upon a calculated travel time for moving the workpiece from a
tooling stage location of one bend to a tooling stage location of a
next bend.
[0057] In accordance with an additional aspect of the invention,
the bend sequence planning module may be capable of querying each
of the expert modules for a subplan and estimated costs. In
addition, each of the expert modules may be capable of responding
to a query by returning a savelist to the bend sequence planning
module, whereby the savelist includes a list of names of
attributes, and values respectively corresponding to the
attributes, to be saved by the bend sequence planning module.
[0058] As a further aspect of the invention, the system includes a
prioritizing mechanism for prioritizing proposed bends in
accordance with bend heuristics determined based upon the geometry
of the workpiece. The generating mechanism may generate a plan,
including a sequence of bends from a first through an Mth bend, by
choosing each bend in the sequence of operations based upon the
prioritized proposed bends and the proposed subplan that
accompanies each proposed bend. The prioritizing mechanism may be
provided with a mechanism far discounting an estimated cost of a
bend having a high priority and increasing an estimated cost for a
bend having a low priority.
[0059] In accordance with a further aspect of the invention, a
determining mechanism may be provided for determining the time
needed for, and the feasibility of, producing one or more parts
with the bending apparatus based upon the generated plan. In
addition, the system may be provided with a mechanism for
performing calculations of the costs of producing a given batch of
parts, based upon the time determined by the determining mechanism.
In addition, or in the alternative, the system may he provided with
a mechanism for redesigning the part based upon the time and the
feasibility determinations made by the determining mechanism. The
system may be further provided with a mechanism for scheduling
manufacturing with the bending apparatus defending upon the
determined amount of time for producing one or more parts.
[0060] In addition to the above-described system, the present
invention is further directed to a computerized method for
selecting a gripper for holding a workpiece. The gripper is
selected for use in a bending apparatus for bending unfinished
workpieces comprising sheets of malleable material. The method
includes reading information describing the geometry of a library
of grippers to be chosen from, forming a set of available grippers
excluding grippers that have certain undesired geometric features,
and choosing a gripper from a set of available grippers. The
gripper is chosen as a function of the width of the gripper, the
length of the gripper, and the knuckle height of the gripper. The
gripper may include a gripper for holding the workpiece while
loading and unloading the workpiece into and from a die space of
the bending apparatus. In this regard, the method may include a
step of predicting, for each gripper within the set of available
grippers, a repo number equal to an estimated number of times the
bending apparatus will need to change the position at which the
gripper is holding the workpiece in order to perform a complete
sequence of bending operations on the workpiece. The smallest
predicted repo number is then determined, and the set of available
grippers is adjusted to include the available grippers having a
repo number equal to the smallest predicted repo number, before
choosing (from among the set of available grippers) a gripper as a
function of the gripper's width, length, and knuckle height.
[0061] The gripper may alternatively comprise a repo gripper for
holding the workpiece while a robot changes its grip an the
workpiece. In this regard, the method may be further provided with
a step of constructing data representations of the respective
intermediate shapes of the workpiece when repo operations are to be
performed by the bending apparatus, and utilizing the intermediate
shapes to determine which grippers are excluded from the set of
available grippers. The grippers that cannot securely grasp the
workpiece, considering all of the constructed intermediate shape
representations, are excluded from the set of available
grippers.
[0062] In addition to the above-described system and method, the
present invention is further directed to a computerized method for
determining a location at which a gripper can hold a malleable
sheet workpiece while a bending apparatus performs an mth operation
an the workpiece. The bending apparatus performs a sequence of
operations, including the mth operation, in accordance with a
bending plan. The sequence of operations includes a sequence of
bends from a first bend through an Nth bend, and the shape of the
workpiece changes to several intermediate shapes as the bending
apparatus progresses through the sequence of a bends. A set of
topographic representation is formed by repeatedly generating,
along edges of the workpiece, as a variable i is varied, a graphic
representation of areas on the workpiece within which the gripper
location can be without hindering performance of an ith operation.
A determination is made as to whether or not the performance of the
ith operation will be hindered by taking into consideration the
intermediate shape of the workpiece when the ith operation is
performed. The method further includes the step of determining the
intersection of all the geographic representations within the set
to thereby determine the areas common to the given plurality of
operations in the sequence of operations. The mth operation may
include changing a robot's grip an the workpiece between bends in
the sequence of bends, and/or performing a bend within the sequence
of bends.
[0063] In addition to the above, the present invention may be
directed to a computerized method for selecting tooling to be used
in a bending apparatus for bending a workpiece comprising a sheet
of malleable material. The tooling includes at least a die and a
punch, and the bending apparatus performs, utilizing the selected
tooling, a sequence of operations comprising a sequence of bends
from a first bend through an Nth bend. The method comprises steps
of reading information describing in the geometry of dies and
punches, and forming sets of feasible dies and punches excluding
dies and punches that have an insufficient force capacity to bend
the workpiece and that are incapable of forming desired bends in
the workpiece resulting in desired angles and desired inside radii.
In addition, the method includes a step of choosing an appropriate
die and appropriate punch that most closely satisfies force, bend
angle, and inside radii requirements, excluding punches that will
likely collide with the workpiece as determined by failure of a
geometric collision test.
[0064] The geometric collision test may be performed by modeling a
finished 3D workpiece and, for each bend in the sequence of bends,
aligning the modeled finished 3D workpiece between a model of each
feasible punch and a model of a chosen die.
[0065] In addition to the above, the present invention may be
directed to a computerized method for determining a layout of
tooling stages along a die rail of a bending apparatus. The bending
apparatus is adapted to bend workpieces comprising sheets of
malleable material, by performing a sequence of operations
comprising a sequence of bends from a first bend through an Nth
bend. The method includes a step of deciding on an arrangement of a
plurality of stages along the die rail and calculating lateral
limits based upon the amount by which the workpiece extends beyond
a side edge of a tooling stage for the bends of the sequence of
bends. In addition, the method includes determining a largest
lateral limit for each side of the stage, and spacing adjacently
arranged stages to have a gap between adjacent side edges that is
greater than or equal to the larger of the determined largest
lateral limits of the adjacent side edges.
[0066] In addition to the above-described system and methods, the
present invention may be directed to a system far generating a plan
and for controlling a bending apparatus. As described above, the
plan comprises a sequence of operations to be performed by the
bending apparatus, and the bending apparatus is adapted to bend
workpieces comprising sheets of malleable material. The sequence of
operations includes a sequence of bends, from a first through an
Nth bend, for forming a finished workpiece from a stock sheet of
malleable material. The system includes a setup planning mechanism
for generating the sequence of bends and a setup subplan that
includes information regarding the manner in which the bending
apparatus is to be set up before commencing the first bend in the
sequence of bends. In addition, the system includes a forwarding
mechanism for forwarding the setup subplan, once generated, to a
signalling device for signalling commencement of setup operations
to be performed in accordance with the setup subplan. A finalize
mechanism is further provided for generating detailed subplan
information to complete the plan after the setup subplan has been
generated. At least part of the detailed subplan information is
generated after the commencement of setup operations has been
signalled by the signalling device. The setup subplan may include
one or more of the following types of information: information
regarding the layout of tooling stages; information regarding
tooling die and punch profiles to be utilized in the bending
apparatus; positions of tooling stages along a die rail of the
bending apparatus; information regarding what type of gripper to
use for manipulating the workpiece through the bend sequence; and
information regarding what type of rep gripper to use for holding
the workpiece while a gripper changes its grasp on the workpiece in
between bends of the bend sequence.
[0067] The forwarding device may include a device for forwarding
instructions to a sequencer module which directs performance of
automated setup operations on the bending apparatus. In addition,
or in the alternative, the forwarding device may also, or in the
alternative, create a visual representation of setup operations to
be performed an the bending apparatus so that a human operator can
thereby perform the setup operations.
[0068] In addition to the above-described systems and methods, the
present invention may be directed to a system for performing setup
operations an a bending apparatus so that the bending apparatus can
be utilized to perform bending operations an workpieces comprising
sheets of malleable material. The bending apparatus includes a die,
a tool punch holding mechanism, and one or more tooling stages.
Each tooling stage includes a die mounted on the die rail and a
tool punch held by the punch holding mechanism. The system further
includes a mechanism for receiving information regarding a location
of each of the one or more tooling stages along the die rail, and a
control mechanism for controlling a position of a guide member
along at least one of a die rail and the tool punch holding
mechanism based upon the received information so that at least one
of the die and the tool punch can be aligned with reference to the
guide member and so that the resulting tooling stage will be at a
desired location along the die rail.
[0069] The control mechanism may be capable of positioning the
guide member to be at a specified position along the die rail and
to be within a certain distance from the die rail, whereby a die of
a tooling stage to be aligned can be abutted against the guide
member in order to properly position the tooling stage along the
die rail. The guide member may include a backgage finger of a
mechanism for performing backgaging when loading a workpiece into
the bending apparatus.
[0070] In addition to the above-described systems and methods, the
present invention may be directed to a system for executing a plan
for controlling a bending apparatus for bending workpieces
comprising sheets of malleable material. The plan includes a
sequence of operations to be performed by the bending apparatus. A
sensor-based control mechanism is provided for performing an
operation, including moving a workpiece from one position to
another, with the bending apparatus utilizing a sensor output to
modify the movements of the workpiece. A measuring device measures
an amount by which the movement of the workpiece was modified due
to the sensor output, and a learned control mechanism performs, the
operation, including moving the workpiece from one position to
another, without modifying the movement of the workpiece utilizing
a sensor output. The learned control mechanism controls performance
of the operation based upon the amount measured by the measuring
device.
[0071] The above-listed and other objects, features, and advantages
of the present invention will be more fully set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] The present invention is further described in the detailed
description which follows, by reference to the noted plurality of
drawings by way of non-limiting examples of illustrative
embodiments of the present invention, in which like reference
numerals represent similar parts throughout the several views of
the drawings, and wherein:
[0073] FIG. 1 illustrates a prior art bending workstation;
[0074] FIG. 2 illustrates part of a side view of a prior art bend
press;
[0075] FIG. 3 illustrates a partial front view of a prior art bend
press;
[0076] FIG. 4 illustrates a prior art bend planning and control
system;
[0077] FIG. 5A illustrates a bend planning and control system
provided in accordance with an illustrated embodiment of the
present invention;
[0078] FIG. 5B illustrates a stage setup controlling system;
[0079] FIG. 5C illustrates a top view of a die rail with a stage
setup operation being performed thereon;
[0080] FIG. 6 illustrates a bend planing and control system with a
detailed diagram of control system 75 as illustrated in FIG.
5A;
[0081] FIG. 7 illustrates a high level flow chart of an overall
planning process to be performed by the illustrated planning
system;
[0082] FIG. 8 illustrates a flat workpiece provided for purposes of
describing labeled geometric bend-related features;
[0083] FIG. 9 illustrates a flat workpiece and a corresponding
search tree;
[0084] FIG. 10 illustrates a thickness transformation of a single
workpiece;
[0085] FIG. 11 illustrates a thickness transformation of an
assembly of workpieces;
[0086] FIG. 12 illustrates a geometric modeling file structure with
and without a thickness transformation;
[0087] FIG. 13A illustrates a plurality of functions of a design
system for intelligent bend planning;
[0088] FIG. 13B illustrates a part modeler for modeling parts based
upon a design system's output shape file;
[0089] FIG. 13C and FIG. 13D respectively illustrate a 2D
representation and a 3D representation of a workpiece;
[0090] FIGS. 14A-14E illustrate an example graphic user interface
of the CAD system provided in the illustrated embodiment, and the
steps of designing a part utilizing such a graphic interface;
[0091] FIG. 15A illustrates a side view of a bent workpiece with
thickness;
[0092] FIG. 15B illustrates a top view of an undeveloped flat 2D
workpiece representation;
[0093] FIG. 15C illustrates a top view of a developed flat 2D
workpiece representation;
[0094] FIG. 16 illustrates a 2D drawing corresponding to a bend
graph listing;
[0095] FIG. 17A illustrates a BM100 geometric modeling filing
structure;
[0096] FIG. 17B illustrates a tooling modeling file structure;
[0097] FIG. 18A illustrates a gripper modeling file structure;
[0098] FIG. 18B illustrates a part modeling file structure;
[0099] FIG. 19 illustrates an FEL planning message to be sent from
a bend sequence planner to a motion expert;
[0100] FIG. 20A presents an example of a workpiece and a search
tree generated in accordance with the workpiece;
[0101] FIG. 20B illustrates an example workpiece and search tree
with bend twin nodes;
[0102] FIG. 20C illustrates an example workpiece and search tree
with a constrained bend twin node;
[0103] FIGS. 20D and 20E illustrate: example workpieces with
co-linear bends;
[0104] FIG. 21 illustrates a general example flow chart of A*
applied to sheet metal bending;
[0105] FIGS. 22A-22D illustrate the main flow of an embodiment of
the bend sequence planner illustrated herein;
[0106] FIGS. 23A-22D illustrate a process for performing
subplanning and cost assignment;
[0107] FIG. 24 illustrates an example workpiece and search tree,
with calculated costs illustrated;
[0108] FIG. 25A is an example workpiece having an inner tab;
[0109] FIG. 25B is an example workpiece with outer and inner bend
lines;
[0110] FIG. 25C is an example workpiece with short and long bend
lines;
[0111] FIG. 25D is an example portion of a bent workpiece, with
abutting inside and outside corner edges;
[0112] FIG. 25E represents an example cutaway portion of a
workpiece with co-linear bends;
[0113] FIGS. 26A, 26B, 27A-27C show example workpieces used to
explain constraint expressions;
[0114] FIG. 28 comprises a graph comparing the histories of nodes
b6' and b6;
[0115] FIG. 29 comprises a chart of a dialogue between the bend
sequence planner and the holding expert;
[0116] FIG. 30 illustrates a chart of a dialogue between the bend
sequence planner and the tooling expert;
[0117] FIG. 31 illustrates a chart of a dialogue between the bend
sequence planner and the motion expert;
[0118] FIG. 32 illustrates a process of the selection of a robot
gripper;
[0119] FIG. 33A illustrates a flat 2D workpiece with discretized x
points illustrated thereon;
[0120] FIG. 33B illustrates a bent 3D workpiece with discretized x
points placed thereon;
[0121] FIGS. 34A-34B illustrate a process for predicting a minimum
number of repos to be performed before the search;
[0122] FIGS. 35A-35B illustrate a process for predicting a minimum
number of repos to be performed during the search;
[0123] FIGS. 36A-36B illustrate a process for determining the
robot's grasp locations an the workpiece;
[0124] FIG. 37 illustrates a 2D workpiece having both sheet and
edge coordinate systems;
[0125] FIG. 38 illustrates a 2D workpiece and the illustrated
generation of available Y grasp locations;
[0126] FIG. 39 is a diagram representing the intersections grasp
regions to determine of a final grasp region before a repo is
performed;
[0127] FIG. 40 comprises examples of grasp regions in different
levels of the search;
[0128] FIG. 41 illustrates a process for determining the repo
gripper location;
[0129] FIG. 42 illustrates a process for selecting a repo gripper
before performance of a state-space search;
[0130] FIGS. 43A-43B illustrate a process for selecting a repo
gripper to be performed after a state-space search;
[0131] FIG. 44 illustrates a bin-packing process to be performed
before a search;
[0132] FIG. 45 illustrates a graphic representation of the steps
utilized to determine an initial tooling h-cost (based upon the
total predicted stages which will be needed to perform the complete
bend sequence);
[0133] FIG. 46 illustrates the steps of a process for determining
the initial tooling h-costs;
[0134] FIG. 47A illustrates a process of selecting tooling to be
used;
[0135] FIGS. 47B-47C illustrate a process for performing stage
planning,
[0136] FIGS. 48A-48C are graphic representations of a modeled bend
press and workpiece which will be utilized during stage
planning;
[0137] FIG. 49 illustrates a process of fine motion planning;
[0138] FIG. 50 illustrates process steps performed by the motion
expert to calculate k and h costs;
[0139] FIG. 51 is a graphic representation of models of a bend
press, a robot, and a workpiece, the models being used for
determining a gross motion plan;
[0140] FIG. 52 is a black diagram which illustrates the structure
of the controller software of the planning system illustrated
herein;
[0141] FIG. 53 illustrates the main process steps of the sequencer
task provided within the sequence of the planning system
illustrated herein;
[0142] FIG. 54 illustrates the steps performed in executing a bend
in accordance with a developed plan;
[0143] FIG. 55 illustrates a robot task which forms part of the
control system;
[0144] FIG. 56 illustrates a press and loader/unloader (L/UL) task
of the control system;
[0145] FIG. 57 illustrates a backgage task of the control system;
and
[0146] FIG. 58 is a flow chart demonstrating the main steps
performed in a learning process that may be performed by the
planning system illustrated herein.
BRIEF DESCRIPTION OF THE APPENDICES
[0147] The present invention is further exemplified by a plurality
of listings which are provided in the Appendices, wherein:
[0148] Appendix A is an output shape file produced by a CAD system
which includes a geometric/topological data structure of a
workpiece as illustrated in FIG. 14E;
[0149] Appendix B comprises an example bend graph listing formed
from the geometric/topological data structure provided in the
listing of Appendix A;
[0150] Appendix C is an exemplary listing representing the FEL
messages that may be generated and forwarded between the bend
sequence planner and various experts during the planning process;
and
[0151] Appendix D is an example specification for a listing which
represents the final plan in FEL which is forwarded from bend
sequence planner to the sequencer of the planning and control
system 71 illustrated herein
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0152] 1. Planning, Setup and Control
[0153] Referring now to the Figures in greater detail, FIG. 5
illustrates a block diagram of an embodiment of a planning and
control system 70 for an intelligent manufacturing bending
workstation. In the illustrated embodiment, planning and control
system 70 includes a CAD system 74, a bend sequence planner 72, a
plurality of experts (sub-planners), and a sequencer 76. Planning
and Control System 70 is connected to hardware and sensors 78 via
an interface 77.
[0154] The experts include a tooling expert go, a holding expert 82
and a motion expert 84. Additional experts may be 30, provided,
such as sensing expert 85 illustrated in dotted lines. Bend
sequence planner 72, experts 80, 82, and 84, and CAD system 74 may
be implemented within a UNIX-compatible environment on a
workstation computer such as a Sparc 10 Sun OS v.4.1.3. Sequencer
76 may be implemented within an additional CPU coupled to the Sun
workstation via a bus adaptor. The bus adaptor may comprise a BIT 3
VME-to-VME bus adaptor which extends between the Sun workstation
and a revote VME bus passive back-plane. The passive back-plane may
hold several interface mechanisms such as VME (Virtual Memory
Extension) boards, which together form part of interface 77 as
illustrated in FIG. 5. Sequencer 76 may be implemented within a
real-time UNIX-compatible multiprocessor operating system such as C
and may be run by the additional CF which is provided in the
computer workstation's back-plane. Accordingly, in the illustrated
embodiment (shown in FIG. 5), CAD system 74, bend sequence planner
72, experts 80, 82, 84 (and 85) and sequencer 76 are each
implemented primarily with software which controls the operations
of a computer utilizing a UNIX-compatible operating system.
Sequencer 76 is implemented within a real-time UNIX-compatible
multiprocessor operating system such as CHIMERA.
[0155] CAD system 74 is utilized to design a sheet metal
configuration, by defining the shape of a stock (flat) sheet metal
part and the bends to be performed on the stock part to form a
desired three-dimensional finished part. In designing the sheet
metal part, CAD system 74 forms one or more information files which
describe the part. As a three-dimensional part is designed, in a
preferred embodiment, the CAD system maintains in memory, and
visually, a three-dimensional representation of the sheet metal
part in parallel with a two-dimensional representation of the part.
The designer may modify the design by adding or removing details to
or from either representation CAD system 74 may also perform
functions such as gathering and/or generating information needed
for geometric modeling and requesting advice from bend sequence
planner 72 as to whether certain design features (an be implemented
by the bending workstations
[0156] Bend sequence planner 72 operates in cooperation with
tooling expert 80, holding expert 82, motion expert 84, and any
other experts (e.g., sensing expert 85) to produce a plan for
complete part production by a bending workstation of the part
designed with the use of CAD system 74. Bend sequence planner 72
performs functions such as proposing a particular bend in a
hypothetical bend sequence, and determining what initial steps must
be performed by the system in order to execute such a bend having a
position within the hypothetical bend sequence. In determining the
consequences of the proposed bend, bend sequence planner 72 may
query tooling expert 80 as to what tooling would be needed to
execute the proposed bend, querying holding expert 82 as to how the
workpiece can be held while performing the proposed bend, and
querying the motion expert 84 as to whether and to what extant the
robot (which is holding the workpiece) can be manipulated to assist
in making the bend. If a sensing expert 85 is provided, bend
sequence planner 72 might query sensing expert 85 as to whether a
particular sensor-based control strategy is needed in order to
facilitate the execution of the proposed bend by the workstation
and the costs associated with a particular sensor-based control
strategy. Bend sequence planner 72 may be configured to continually
propose bends from a first bend consecutively to a last bend in a
complete bend sequence, thus resulting in a complete set of bends
to perform the final workpiece. Once the successful final bend
sequence has been generated in this manner, bend sequence planner
72 may be configured to generate a final plan (which includes a
general list of steps and accompanying information needed to
control execution of the various hardware elements of the
workstation), and forward the plan to sequencer 76.
[0157] Sequencer 76 directs execution of the plan developed by bend
sequence planner 72. Sequencer 76 interprets commands given by bend
sequence planner 72 in the resulting plan, and controls timing of
the various commands by parsing the commands and information
accompanying the commands and placing them into queues provided for
each of the main hardware elements of the sheet metal bending
workstation.
[0158] Controller 75 comprises a plurality of tasks which
correspond to the various hardware elements of the workstation.
Each task is activated by the sequencer in an appropriate manner in
accordance with the plan forwarded by the planner.
[0159] (a) The Planning System Operations: Planner and
Sub-Planners
[0160] Bend sequence planner 72, and the several sub-planners
including, e.g., tooling expert 80, holding expert 82 and motion
expert 84, (and sensing expert 35), form a planning system 71.
[0161] Bend sequence planner 72 analyzes the designed part (Sheet
metal workpiece), provided by CAD system 74, and offers a bend
sequence to be performed by the bending workstation. Planner 72
utilizes a state-space search method in order to determine an
efficient sequence of bend operations that can be utilized by the
bending workstation. Planner 72 converses with tooling expert 80,
holding expert 82 and motion expert 84 in order to obtain the
information it needs to make its decisions.
[0162] Tooling expert 80 responds to queries made by planner 72,
and provides information to the bend sequence planner such as which
tools will be needed for a particular bend operation or bend
sequence. In addition, tooling expert 80 may inform bend sequence
planner 72 of the arrangement of tools within the workstation.
Tooling expert, in conjunction with planner 72, will attempt to
design a setup of tooling so that the fewest number of
stages/toolings are utilized to make a particular part, i.e., to
execute a complete bend sequence for making the part.
[0163] Holding expert 82 makes holding-related determinations, such
as, e.g., whether the robot can hold the workpiece while a
particular bend, specified by bend sequence planner 72, is being
performed. Holding expert 82 may also determine the location at
which the robot should hold the workpiece so that the workpiece may
be maneuvered through a series of bends, without collision, and
without the need to change the robot's grasp on the workpiece. In
addition, holding expert 82 may determine the position at which the
repositioning gripper should hold the workpiece when the robot's
grasp is being changed, and where suction cups 31 of
loader/unloader (L/UL) 30 should be placed during unloading and
loading of the workpiece.
[0164] Motion expert 84 is responsible for generating a motion
plan, i.e., the manner in which the robot should be maneuvered in
order to move the workpiece through various spaces and along
various routes as needed to execute the bends.
[0165] Bend sequence planner 72 and the respective experts may be
modular to communicate with each other in a query-based manner. For
example, before deciding to include a particular bend as part of
the bend sequence, bend sequence planner 72 may query tooling
expert 80 as to whether there are sufficient tools to handle the
bend. Bend sequence planner 72 will then await a response from
tooling expert 80. Tooling expert 80 will recognize the query from
bend sequence planner 72, and will return with a response, e.g.,
indicating that there are sufficient tools to handle that
particular bend noted by bend sequence planner 72. By way of
example, bend sequence planner 72 may, also ask holding expert 82
if robot arm gripper 14 can remain holding onto the workpiece
during a particular bend operation without repositioning its grasp
of the workpiece. Holding expert 82 will then respond to the query
made by bend sequence planner 72, and bend sequence planner 72 will
then utilize the information to perform its next determination.
[0166] Each of the modules of planning system 71 utilizes one or
more functions provided by a geometric modeling library (not shown)
in order to model the relative interactions and positions of each
of the hardware components of the system as may be needed in making
their determinations.
[0167] (b) System Setup
[0168] Once a plan is generated by the planning system, the system
will perform a setup process. The setup process can be performed
completely manually, or it may be automated in full or in part with
the use of automated tool changers. The manual activities to be
performed during the setup process may include downloading program
data to dedicated controllers such as those illustrated in FIG.
1.
[0169] As shown in FIG. 5D, each stage (stage 1 and stage 2 as
illustrated in FIG. 5D) must be set up by placing a plurality of
die segments 810a, 810b, and 310c in stage 1, and 811a, *811b, and
811c for stage 2 along die rail 22. In order to gauge the location
at which die segments for each stage will be placed, a human
operator will typically measure the distance from the edge of the
die rail 22 to a particular edge of the die corresponding to each
stage. For sample, a measurement may be made from the left edge of
die rail 22 to the left edge of each die set for each stage in
order to position the die segments corresponding to each stage.
Pursuant to a particular embodiment of the present invention, a
mechanism may be provided for automatically providing a guide that
can be used by the setup operator to place the die segments at the
appropriate location along die rail 22. Such a mechanism may
comprise a backgage finger 88 which can be automatically positioned
at a particular edge of each stage along die rail 22. For example,
backgage finger 83 may be first located at location A for purposes
of abutting first die segment 810a against backgage finger 88, and
subsequent installment of second and third die segments 810b and
810c. After aligning die segments for stage 1, backgage finger 88
may be automatically positioned to the next stage, i.e., stage 2.
More particularly, backgage finger 88 may be positioned at one side
of the die corresponding to stage 2. In the illustrated example,
backgage finger 88 is positioned at the left edge of die 811. While
backgage finger 88 is at that position, first die segment 811a may
be placed along die rail 22 and abutted against backgage finger 88
for alignment. Thereafter, die segments 811b and 817c may be placed
on and secured to die rail 22.
[0170] FIG. 5c illustrates the main components for controlling the
backgage finger 88 to assist in positioning an alignment of dies
810 and 811. The subsystem comprises an input control module 87a
which includes a mechanism for instructing backgage servo
controller 87b to move backgage finger 88 to one or more particular
stage locations.
[0171] According to FIG. 5A, alignment control module 87a may be
provided in control portion 75 of planning and control system 70a
while backgage servo controller 87b may be provided with an
interface 77. More specifically, controller 75 may be provided with
a backgage task module. The backgage task module may be provided
with a backgage finger die-alignment function which may be, called
by the backgage task module. In calling the die-alignment function,
the backgage task module may activate and control a backgage servo
controller through the use of a second level backgage device driver
206 (see FIG. 6), which in turn interacts with an appropriate level
1 device driver such as an I/O device driver 220 which interacts
with a parallel I/O card connected to the backgage hardware of the
bending workstation.
[0172] Another manual step that can be performed is positioning
and/or adjusting of the punch holders 20. In addition, standard
steps may be performed to align tool punch segments so that they
are properly seated within each punch bolder 20 and correspond to
the associated die segments is may comprise operating the press so
that the die segments and corresponding tool punch segments
are-compressed against each other with a set amount of force. In
addition, other standard adjustments and procedures, known to those
skilled in the art, may be performed during setup. For example,
loader/unloader 30 may need to be adjusted so that suction cups 31
are properly positioned with respect to the workpiece 16.
[0173] Workstation 10 may be configured to be controlled
automatically by the planning system, without any need for human
intervention. In the event that certain control modules are still
maintained as separate, e.g., separate robot control module 44 as
shown in FIG. 1, along with separate press brake controller 42 and
load/unload controller 46, the planning system may be configured to
download appropriate components of the plan to the appropriate
control modules.
[0174] (c) Sequencing and Control
[0175] In the illustrated embodiment, sequencer 76 is implemented
within a real-time UNIX-compatible shell such as an Ironics IV-3230
computer with a CHIMERA II operating system. Additional information
regarding possible implementations of a real-time scheduler such as
sequencer 76 is provided in the CHIMERA manual by Stewart, Schmitz
and Khosla, entitled "CHIMERA II Real-Time programming Environment,
Version 1.02" (Oct. 29, 1990), the content of which is incorporated
by reference herein in its entirety. Sequencer 76 schedules the
general execution ol the generated plan by control system 75, which
utilizes interface architecture 77 to communicate with various
hardware elements and sensors within the system, depicted as
hardware and sensors 78 in FIG. 5.
[0176] FIG. 6 depicts in greater detail, sequencer 76, control
system 75, and interface architecture 77. As illustrated in FIG. 6,
sequencer 76 is connected to bend sequencer planner 72 and is
further connected to a plurality of modules which comprise control
system 75. The modules of control system 75 include a robot task
92, a press and L/UL task 94, a backgage task 96, a motion library
98, a speed control module 102 and a collision detection module
100. Interface architecture 77 comprises a set of level 2 device
drivers and another set of level 1 device drivers. The level 2
device drivers (DD's) may include robot DD 202, press and L/UL DD
204, backgage DD 206, gripper DD 208, gripper sensor DD 210, drop
sensor DD 212, backgage sensor DD 214, and angle sensor DD 216. The
level 1 device drivers may include respective device drivers 220,
222 and 224 for one or more parallel I/O VME cards, one or more A/D
VME converter cards, and a robot servo control card.
[0177] Accordingly, as illustrated by interface architecture 77, a
two-level device driver format is recommended for interfacing the
various tasks and control modules of control system 75 to the
various hardware elements of the bending workstation. The first
level device drivers comprise a UNIX-like interface, with commands
supported including open ( ), close ( ), read ( ), write ( ), ioctl
( ), and mnap ( ) commands. The first level device drivers
standardize the interface to the I/O ports to which the hardware
devices are attached, such as parallel I/O ports, analog/digital
converters and a robot servo control mechanism. The second level
device drivers form an interface between the various modules of the
control system 75 and the first level device driver. Although there
is no standard interlace routines provided for the second level
device drivers, the second level device drivers may be implemented
with the use of a standard farm as disclosed in the above-noted
CHIMERA manual. With the use of a two-level device driver format, a
software interface system may be provided which is reliable,
portable, and has code which is easily readable. Specific details
regarding the device drivers, and examples implementations thereof,
are provided in the above-noted CHIMERA manual, which has been
incorporated by reference herein.
[0178] As to the VME cards which are the actual I/O parts
connecting the computer to the hardware elements, such cards may
include, as noted above, one or more parallel I/O cards, such cards
preferably having optically isolated connections between the
commuter and the various hardware elements connected thereto. In
addition, the VME cards may include one or more Geonics motion two
axis servo control cards II MCCII and one or more A/D converters
having sufficient a number of channels and bit resolution, e.g., an
A/D converter with 16 channels and 12 bit resolution, such as the
IXV-1645 Ironics (Pentland-Burr-Brown MV 950S). The parallel I/C
cards may include an 80-channel (with 64 usable channels) Xycom
XVME-240 card and/or 32-channel digital output boards such as the
Xycom XVME-220 and/or XVME-212 boards. One or more A/D converters
can be provided for inputting information such as reading various
data produced by the sensors included in the workstation, such as a
gripper sensor, droop sensor, backgage sensor, and/or angle
sensor.
[0179] Each of the robot task 92, press and L/UL task 94, and
backgage task 96, control the appropriate device drivers for
controlling the corresponding hardware elements of the bending
work-station. Several functions which must be performed during
execution of various motion-related functions may be provided in
motion library 98. Such functions may include kinematics,
trajectory calculations and filtering. Any control functions
relating to speed control, i.e., controlling the speed with which
various physical elements (such as the robot) of the bending
workstation are moved, may be implemented within speed control
module 102. Collision detection module 100 is provided in order to
perform collision detection which is needed in certain motion
control processes during execution of the bend process.
[0180] Motion library 98 may further include dynamic motion control
and sensor-based motion control modules which directly communicate
with the second-level device drivers for dynamically controlling
the movement of various components of the bending workstation and
for changing such control in accordance with sensor-based signals
produced by the various sensors provided in this system.
[0181] It is noted that in the parallel I/O cards it is preferred
that the computer be optically isolated from the actual hardware
connections to prevent damage that may be caused by surges present
at the hardware components. Other reasons for optically isolating
the parallel I/a cards is to protect the computer and the car and
to prevent the occurrence of ground loops. However, it is not
necessary that the A/D converters be optically isolated from the
sensors.
[0182] 2. Bend Sequence Planner
[0183] Bend sequence planner 72 of the embodiment shown in FIG. 5A
performs three main functions. It generates a bend sequence,
including accompanying operations associated with each bend,
queries experts as to the consequences of the bend sequence as it
is generated, and as to further plan details (subplans) needed to
accomplish the generated bend sequence, and compiles all
gathered/generated information in order to form an overall plan.
The plan specifies the-steps needed to execute the bend sequence by
a control system which controls operations of the sheet metal
bending workstation. Each of the experts of the illustrated
planning system 71 performs three main functions when requested by
planner 72. They each determine an incremental cost for performing
an individual step within the bend sequence, develop
proposed/intermediate plan information, and communicate the
incremental cost and plan information to bend sequence planner 72.
The proposed/intermediate plan information includes two types of
information: definite information and indefinite information. For
example, at a certain paint in time during planning, holding expert
82 will know which regions of the workpiece may be grasped by the
robot grasper to perform a given bend within a bend sequence (the
grasp regions being definite), but will not yet know the exact
grasp location (the precise grasp location being indefinite). A
temporary (indefinite) grasp location will be assigned by the
holding expert 82, which can be verified at a later time. As noted
above, sequence planner will query each expert as to the
consequences of a bend sequence as it is generated.
[0184] The consequences of the bend sequence are represented in
terms of cost. The costs of the bend sequence as it is generated
may be determined as a function of one or more of: the amount of
time that it takes to perform a particular operation within the
bend sequence, the extent to which an operation within the bend
sequence will affect the accuracy of the operation and the quality
a the resulting workpiece, whether or not there are any safety
concerns associated with performing a particular operation at a
particular point in a bend sequence, and whether there are any
heuristics which, if taken into account, would suggest performing
one operation instead of another at a particular point in the bend
sequence.
[0185] Bend sequence planner 72 may query experts for information
such as what tool profile should be utilized to perform certain
bends of the bend sequence, what stage segments will be needed to
farm a given stage which will be needed to perform a bend, and
where can/should the robot gripper grasp the workpiece in
performing one or more bends of the bend sequence. In addition,
planner 72 may query the experts as to when a repositioning of the
workpiece should be performed in the bend sequence, and how should
the robot and the workpiece be moved in order to execute various
operations throughout the sequence, such as a bend, repositioning,
workstation load, and/or a workstation upload. FIG. 7 represents,
in a high level flow chart, the major steps performed by an example
embodiment of bend sequence planner 72. In a first step S1,
parallel design processing is performed by CAD system 74. The
parallel design processing may comprise, among other functions,
labeling various geometries corresponding to respective portions of
the workpiece, the resulting labels being used later (in step S3)
by the bend sequence planner to determine whether heuristics should
be considered in generating the bend sequence plan. Subsequently,
in step S2, a heuristics framework is produced to guide the bend
sequence planner in choosing the bends that will form the bend
sequence. In producing the heuristics framework for the bend
sequence in step S2, a partial order of bending steps is computed
that complies with certain specified heuristics. Subsequently, in
step S3 a state-space search algorithm is performed which will be
influenced by the heuristics framework. The state-space search
algorithm performs an analysis of the implications of performing
various bends in a prescribed order, by assigning costs to each
bend in step S4. In order to help with the assignment of costs, in
step S5, geometric reasoning is utilized, e.g., to determine the
physical implications a Particular bend will have by modeling the
machine and the resulting workpiece as theft relate to each other
during the execution of each bend.
[0186] The heuristics are taken into account by either reducing the
assigned costs for a particular bend (if it is preferred due to
heuristics) or by increasing the assigned costs (if the bend is not
preferred due to heuristics). A particular sequence of bends is
thus developed in step S3, which can be executed to produce the
desired finished workpiece. Once the state-space search algorithm
is performed in step. S3, a determination is made in step S6 as to
whether or not a complete plan, including a complete bend sequence,
has been generated. If a plan cannot be formed for the design that
has been specified, the process returns to step S1, where the
workpiece may be redesigned to form a part design for which an
operational plan can be created.
[0187] If a determination is made in step S6 that a complete plan
was produced, the process will proceed to step S7, and the complete
plan will be forwarded, using FEL, to the sequencer, or the plan
may be stored in a file for later retrieval and execution by the
sequencer. The state-space search algorithm will preferably
comprise an A* algorithm, such as disclosed, e.g., by Nils J.
Nilsson in "Problem-Solving Methods in Artificial Intelligence"
McGraw-Hill Back Company, 1971, pages 43-67, the content of which
is expressly incorporated herein by reference in its entirety.
[0188] It is noted that the cost assignment step S4 may consider
variables such as robot motion, gripping positions, the need for
regripping, the need to change the gripper, tooling positions, and
the need to change the tools sign costs are assigned for variables
that will be time consuming, sacrifice quality, and/or expose the
system to high risk.
[0189] The above-described operations planning method can be termed
generative planning (since it automatically generates a bending
plan), with weak heuristics and state-space searching. In
performing the method, a human inputs the design. A heuristics
framework is defined using heuristics which are called "weak
heuristics" because they comprise only a limited set of rules.
Possible bends are considered, and costs are assigned to each
considered bend. The costs assigned to the bends are influenced by
the heuristics framework by augmenting or discounting the cost of a
particular bend. A sequence of bends of the least total cost is
chosen utilizing a state-space searching algorithm.
[0190] Generative planning with weak heuristics as disclosed herein
should be contrasted with other approaches to operations planning.
One such approach includes variant planning with case-based
reasoning. In variant planning, a hand inputs a design of a new
part, and the design is coded according to an index. The index is
used to lack up an old design which best resembles the current part
to be designed and the problems to be solved A human operator edits
the old plan to solve the new problems, e.g., by editing an MM
program. One of the problems noted with variant planning is that a
similar design may require different or divergent solutions, which
will not be discovered by comparison to old plans.
[0191] Another approach to operations planning is generative
planning with strong heuristics. With generative planning with
strong heuristics, the human inputs the design and several labeled
features of the new part. Heuristics are then used to determine the
total ordering of bends and machine operations, thus being called
"strong heuristics." A generative planning system with strong
heuristics lacks the flexibility and intelligence of a generative
planning system with weak heuristics, and will likely be unable to
handle unorthodox problems. Such a system has no understanding as
to what heuristics work better in a particular situation, and which
heuristics should be discarded. Moreover, such a system will be
incapable of developing a plan in many cases.
[0192] (a.1) Heuristics
[0193] Sheet metal bending heuristics can be taken into account by
the bend sequence planner of the present invention. Several
exemplary bend heuristics will be described as follows. One
heuristic is to bend internal tabs early. FIG. 25A illustrates a
workpiece 16 having an internal tab 33 which is to be bent along
bend line 34a. In accordance with this heuristic, although there
are other bends to be performed along bend lines 34b, 34c, and 34d,
it is preferred that the internal tab 33 be bent along bend line
34a first.
[0194] In accordance with another heuristic, it is desired that the
bends along the outermost bend lines be performed before the bends
along the inner bend lines. For example, referring to FIG. 25B, a
workpiece 16 is shown which includes outer bend lines 35a, 35b,
35c, and 35d, along with inner bend lines 36a, 36b, 36c, and 36d.
In this illustrated example, in accordance with the heuristic, it
is desired that the outer bends corresponding to outer bend lines
35a-35d be performed before the bends corresponding to inner bend
lines 36a-36d.
[0195] In accordance with a third heuristic, it is preferred that
shorter bends be performed before longer bends. FIG. 25C
illustrates a workpiece having shorter bends along bend lines 37a
and 37b, and longer bends along bend lines 38a and 38h.
Accordingly, it is preferred that the bends along bend lines 37a
and 37b be performed before the bends along bend lines 38a and
38b.
[0196] In accordance with a fourth heuristic, it is preferred that
bends which form an outside face, of a corner of a 3D workpiece, be
performed before the abutting inside corner fase. FIG. 25D
illustrates a workpiece 16 having an outside face 39a and an inside
face 39b which each abut each other at a corner 390. If the bend
corresponding to the inside face was done first, then, when
performing the bend corresponding to the outside face 39a, the
press would not be able to cause the flange to be bent beyond its
intended 90 angle. Accordingly, when the outside face springs back,
it will not be flush with the end portion of inside face 39h.
[0197] In accordance with an additional heuristic, co-linear bends
are performed simultaneously. As shown in FIG. 25E, a workpiece 16
is shown to include two tabs 26a and 26b, which are each to be bent
along bend lines 27a, 27b, respectively. Since the bend lines 27a
and 27b are co-linear, in accordance with the heuristic, it is
preferred that the bends along those bend lines will be performed
simultaneously.
[0198] The above-described heuristics are only examples of the
types of heuristics which may be taken into account by the bend
sequence planner of the present invention. A larger or smaller set
of heuristics, including all or a portion of the above-listed
heuristics, may he utilized by the bend sequence planner.
[0199] In order to recognize when certain heuristics may apply to a
given workpiece in developing the plan, a list of key features may
be created which describe various geometric features of the
workpiece which can then be utilized by the bend sequence planner
in applying the heuristic rules. A list of key features may be
described with respect to the example workpiece 16 illustrated in
FIG. 8. Several features may be deduced from workpiece 16, while it
is still in its 2D state. An example of such features may include
the flange number, the width of the flange, and the height of that
flange. Referring, e.g., to flange 7, the flange number of the
flange would be 7, a value w would he assigned-to the width of that
flange, and a value h would be assigned as the height of that
flange. In addition, values may be defined which specify an
angle-class, i.e., a class of flanges which all have the same bend
angle.
[0200] Additional features which may be labeled to avoid extra
searching in the search space include an indication that the part
that is symmetric around one or more axes.
[0201] FIG. 8 illustrates a workpiece 16 and a search tree 15
corresponding thereto. Workpiece 16 has an axis of symmetry Y which
is divided down the middle, running longitudinally through
workpiece 16. Accordingly, at the first level of the search, the
nodes corresponding to bends 3 and 5 have been eliminated (as
indicated by the circles surrounding these bends) because they are
symmetrical with nodes 2 and 4. There is no need to also evaluate
and search through bends 3 and 5 at the first level, since the same
effective results would be obtained if the search started with the
bend corresponding to those nodes as opposed to either of bends 2
and 4. If the first bend chosen is bend 1, at the next level of the
search, bends 2 and 4 are still symmetrical with bends 3 and 5.
Thus, the nodes corresponding to bends 3 and 5 are again eliminated
due to the fact that they are symmetrical with bends 2 and 4.
However, if the node corresponding to bend 4 is the first chosen
node in the sequence, this eliminates the symmetry of workpiece 16.
Thus, at the next level of the search stemming from the node of
bend 4, there are no nodes eliminated due to symmetry.
[0202] (a.2) Constraints
[0203] Depending upon the geometric features associated with a part
to be formed, there may be bend-related operations which cannot be
performed at certain points in the operations sequence being
planned. These bend-related operations can be constrained to (or
excluded from) certain locations in the bend sequence by using a
mechanism referred to as a "constraint". A feature extraction
module (not shown) may be provided to automatically label geometric
features from geometric models produced by the design system (e.g.,
using data structures similar to those indicated above), and the
geometric feature labels can be used to form legal phrases (called
constraints) in an interface communication language, such as
FEL.
[0204] Constraints may be defined by using a data structure that
allows a particular arrangement of bend operations to be specified,
in varying degrees of flexibility. For example, for a four-sided
part 16 as illustrated in FIG. 26A, the following constraint
statement can be used to specify the order in which bends 1, 2, 3,
and 4 are performed:
[0205] (constraints ((1 2 3 4)))
[0206] This statement signifies that the first bend must be
performed before the second, which must be performed before the
third, which must be performed before the fourth. Further, since
there are no operators included in the statement, there may not be
any other bend operations performed before, between, or after any
of bends 1-4.
[0207] If the bend 2 must be performed before bend 3, but there are
no other constraints on the arrangement of the bend operations in
the bend sequence, the following constraint statement may be
used:
[0208] (constraint ((*2*3*)))
[0209] The operator "*" acts as a "wild card", and allows either no
bend operations or any number of bend operations to be performed at
its location in the bend sequence, and the type of bend operations
which may be performed at its location can be among any of the
remaining bend operations not specified in the constraint
statement.
[0210] Another wild card operator, "?" can also be used, and it
signifies that exactly one bend operation, among those not
specified in the constraint statement, must be performed at its
location in, the bend sequence. Thus, if precisely one bend
operation must be performed before bend 2 in the part shown in FIG.
26A, but there is no limitation an the number or type of bend
operations following bend 2 (except that they may not include bend
2), the following constraint statement can be used:
[0211] (constraint((?2*))).
[0212] The constraint statements may also include grouping
operators, which require that certain bend operations be grouped
together with no limitation an the order of the bend operations
with the grump. For example, the following constraint statement
requires that bends 2 and 3 be before bend 4 in the bend sequence,
and that bends 2 and 3 be grouped together with no bend operations
therebetween:
[0213] (constraints((*{2 3}*4*))).
[0214] More than one constraint expression can be included within a
constraint statement. Far example, the following constraint
statement includes the above grouping constraint expression, as
well as an additional constraint expression which further specifies
that bend 1 must be before bend 4 without any additional
limitations as to the inclusion and arrangement of the other
operations with respect to bends 1 and 4:
[0215] (constraints((*{2 3}*4*)
[0216] (*1*4*))).
[0217] There can be any number of bend operations within a group,
and groups can be nested in order to specify that there is no
requirement that a plurality of groups be in a specific order. For
example, the following expression specifies that bends 1 and 2 must
be next to each other in the bend sequence, and bends 3 and 4 must
be next to each other in the bend sequence. However, there are no
other constraints as to the inclusion and arrangement of other bend
operations due to this constraint expression.
[0218] (*{{1 2}*{3 4}}*).
[0219] Some additional example constraint expressions may include
(*7) which means that bend operation 7 must be performed as the
last bend operation in the sequence, and (*7?), which means that
bend operation 7 must be performed as the second to last bend
operation in the sequence.
[0220] The types of operators that can the used to define
constraints may be expanded to include boolean operators such as
NOT, CR, and AND. For example, a constraint which uses a NOT
operator could be (* NOT 7), which would mean that the seventh bend
operation could not be the last operation of the sequence.
[0221] There is virtually no limit to the types of constraints that
can be specified, and any entity in the planning system, including
the various experts as well as a human operator of the bend
sequence planner, can define constraints. A constraint manager may
be provided, e.g., within the bend sequence planner, in order to
help maintain the consistency of constraints and resolve conflicts
that arise between constraints.
[0222] By way of example, the types of constraints may include
constraints for (1) channels (e.g., as shown in FIG. 26B), (2)
angle bends, where the bend line for the flange to be bent
intersects and is close to a non-end point portion of a bend line
of another bend (and both of the bends are to be performed in the
same direction, e.g., they are both positive bends) (e.g., as shown
in FIG. 27A), and (3) flanges which when bent form a corner with an
outside flange and an inside abutting flange (e.g., as shown in
FIG. 27C).
[0223] The constraint expression far the channel illustrated in
FIG. 26B usually must be (*2*1*2*), even though a common heuristic
prefers that bends an outer bend lines be performed before those of
inner bend lines, which might suggest a constraint of (*3*2*1*).
This conflict in constraint expressions, if it existed, would have
to be resolved in favor of the channel constraint (*2*1*3*).
[0224] The constraint expression for the pair bends shown in FIG.
27A may be as follows:
[0225] (*2*1*).
[0226] If the order of bends were different, i.e., if bend 1 was
performed before bend 2, the flange of bend 2 would not be bendable
beyond 90 degrees, and thus could not be properly performed (since
when bending malleable materials with elastic tendencies such as
sheet metal the part must be bent slightly beyond the goal angle of
the bend).
[0227] The constraint expression far the pair of bends shown in
FIG. 27C may be as follows:
[0228] (*2*1*).
[0229] The importance of complying with this constraint is
explained above with respect to FIG. 25D.
[0230] Where appropriate, a human operator of the bend sequence
planner (or another expert/subplanner of the system) may define a
constraint expression which groups all bends on each side of a part
together, so that less time will he spent by switching between
sides of the part when performing a search for a solution bend
sequence. FIG. 27B shows a part with several bends on each side of
the part, where it may be appropriate to group the bends for each
side, e.g., by using the following constraint expression:
[0231] (*{{1 2} {3 4} {5 6}}*).
[0232] Since constraints may conflict, a mechanism should be
provided for resolving conflicts. As noted above, a constraint
manager may be provided within the bend sequence planner for this
purpose. A possible prioritization scheme could simply discard or
ignore constraint expressions that have a higher assigned priority.
The priority assigned to constraint expressions could depend upon
what type of constraint it is. For example, human input constraints
could be assigned the highest priority, with machine constraints,
part constraints, and optimization constraints being assigned
respective lower priorities. Accordingly, machine constraints would
have the second to highest priority, part constraints would have
the third highest priority, and optimization constraints would have
the fourth highest (i.e., the lowest) priority.
[0233] A human input constraint is a constraint input by a human
operator controlling the bend sequence planner through a human
interface. A machine constraint is a constraint dictated by
limitations of the machines and tooling (e.g., a channel
constraint). A part constraint is a constraint dictated by the
features of the part (e.g., a constraint dictated by the presence
of inside and outside abutting corners). Optimization constraints
are constraints that are created in order to speed up the search
for a bend sequence (e.g., a constraint to group bends together
that are on a particular side of the part).
[0234] In order to determine if there is a conflict between
constraint expressions, an algorithm may be provided which first
checks for the presence of common operations within a given pair of
constraint expressions. If there is a common operation among the
constraint expressions, they may then be merged together in order
to determine if they conflict. For example, if (*1*2*) was merged
with (*2*3*), the resulting merged constraint expression would be
(*1*2*3*). If (*1*2*) was merged with a conflicting expression such
as (*2*1*), a null would be the result, thereby indicating that the
constraint expressions conflict with each other.
[0235] (a.3) Co-Linear (and Compatible) Bends
[0236] If two bends have bend lines that are co-linear, e.g., bends
5 and 6 in FIG. 8, and they are compatible (i.e., they have the
same bend angles, the same bend radius, and other features which
allow the bends to be performed simultaneously), it is preferred to
have the bends performed simultaneously. For this purpose,
heuristics may be provided in order to influence the search
performed by the bend sequence planner so that simultaneous bending
of co-linear bends is preferred and thus mare likely to become part
of the bend sequence formed by the search. In addition, or
alternatively, constraints may be specified using constraint
expressions to require that certain compatible co-linear bends be
performed simultaneously if possible (i.e., if the constraint
expression does not conflict with a constraint expression of higher
priority).
[0237] (b) The Bend Sequence Planner's State-Space Search
Algorithm
[0238] In a state-space search algorithm, a solution is obtained by
applying operators to state-descriptions until an expression
describing a goal state is obtained. In performing a state-space
search method, a start node is associated with an initial
state-description, and successors of the start node are calculated
using operators that are applicable to the state-description
associated with the node. By calculating all of the successors of a
node, the node is thereby expanded.
[0239] Pointers are set up from each successor node back to its
parent node. The pointers may later be used to indicate a solution
path back to the start node, when a goal node is finally found.
[0240] The successor nodes are checked to see if they are goal
nodes by checking the associated state-descriptions corresponding
to the successor nodes to see if they describe the goal state. If a
goal node has not yet been found, the process of expanding the
nodes, and setting up corresponding pointers, continues. When a
goal node is found, the pointers are traced back to the start node
to produce a solution path. The state-description operators
associated with the arcs of the path are then assembled into a
solution sequence.
[0241] The above-described steps form a state-space search
algorithm. Variations of the above-described algorithm may be
defined by the order in which the nodes are to be expanded. If the
nodes are expanded in an order in which they are generated, the
search method is called a breadth-first method. If the most
recently generated nodes are expanded first, the method is called a
depth-first method. Breadth-first and depth-first methods are
blind-search algorithms, since the order in which the nodes are
expanded is unaffected by the location of the goal node.
[0242] Heuristic information, about the overall nature of the graph
and the general direction of the goal, can be utilized to modify
the search process. Such information can be used to help direct the
search toward the goal, in an attempt to expand the most promising
nodes first one type of heuristic search method is described, e.g.,
by Nils C. Nilsson in "Problem-Solving Methods in Artificial
Intelligence," noted previously.
[0243] Blind-search algorithms, such as breadth-first or
depth-first, are exhaustive in their approach to find a solution
path to a goal node. In application, it is often impractical and
time-consuming to use such methods, because the search will expand
an excessive number of nodes before a solution path is found. Such
an exhaustive expansion of nodes consumes more computer memory in
order to store the information associated with each node, and more
time, e.g., to calculate node expansions and points. Accordingly,
efficient alternatives to blind-search methods are preferred.
Heuristics may be applied to help focus the search, based upon
special information that is available about the problem being
represented by the graph. One way to focus the search is to reduce
the number of successors of each expanded node. Another way to
focus the search is to modify the order in which the nodes are
expanded so that the search can expand outwardly to nodes that
appear to be most promising. Search algorithms which modify the
ordering of node-expansion are called ordered search algorithms.
Ordered search algorithms use an evaluation function to rank the
nodes that are candidates for expansion to determine the node which
is most likely to be an the best path to the goal node. In
operation of the ordered search algorithm an f value is determined
at each node n.sub.f available for expansion, where f is an
estimate of the cost of a minimal cost path from the start node to
the goal node constrained to go through node n.sub.f. Each
succeeding node having the smallest f value is then selected in
sequence for expansion.
[0244] FIG. 20A illustrates a tree produced by an ordered-search
algorithm applied to a blank workpiece that has four sections,
which are to be bent upward to form four sides of a box, each side
being represented in FIG. 20A by a corresponding number 1, 2, 3,
and 4. Each numbered side of the box corresponds to a particular
bend, including bend 1, bend 2, bend 3, and bend 4.
[0245] The blank workpiece (stock part) corresponds to start node
n.sub.0 which may also be called the root node associated with the
initial state-description of the workpiece. The successors of the
start node n.sub.0 may be calculated by expanding the start node
(the root node) to form successor nodes n.sub.1, n.sub.2, n.sub.3,
and n.sub.4. At this level of the search, nodes n.sub.1-n.sub.4
correspond respectively to bend 1, bend 2, bend 3, and bend 4
[0246] Node 1 is sanded to include successor nodes n.sub.5,
n.sub.6, and n.sub.7 which correspond respectively to bend2, bend3
and bend4, and an additional successor node n.sub.8 which
corresponds to a repositioning (i.e., a repo) of the robot
gripper's hold on the workpiece. Node 5 is expanded to include
successor nodes n.sub.9 and n.sub.10, which correspond respectively
to bend3 and bend4, and an additional successor node n.sub.8 which
corresponds to a repo. Node n.sub.8 is expanded to have successor
nodes n.sub.13 and n.sub.14 which correspond respectively to bend4
and a repo. Node n.sub.14 is expanded to have a successor node
n.sub.14 which is the goal node, because it results in the final
bend for the workpiece.
[0247] Bend sequence planner 72 preferably is configured to perform
a best-first state-ace search in order to develop a complete bend
sequence to be performed by the bending workstation. An ordered
search algorithm utilizes an evaluation function to rank nodes that
are candidates for expansion to deter ne the node which is most
likely to be on the best path to the goal node, i.e., the node
which is the best. The first node corresponds to the flat part,
e.g., as illustrated in FIG. 20A. At each level of the search, the
best node which is on an OPEN list will be expanded, and the
expanded node will be taken off OPEN. Depending an whether or not
there are constraints concerning the ordering of certain
operations, all or a portion of the expanded nodes will be placed
an OPEN. The expanded nodes which are placed an OPEN will
correspond to the remaining bend operations, minus those eliminated
due to constraints.
[0248] In accordance with a particular embodiment of the present
invention, there will be twin nodes corresponding to each bend,
including a first twin node corresponding to operation of the bend
while holding the workpiece from one side of the workpiece, and a
second twin node corresponding to performing the same bend, but
while holding the workpiece from the other side of the workpiece.
The expanded nodes which are placed an OPEN may also include one
node that represents a repositioning of the robot gripper's grasp
an the workpiece (i.e., a "repo"). In accordance with a further
feature of the present invention, certain levels of the search may
be constrained so that they do not include a node for a repo. This
is because it would not make sense to perform a repo at one level
of the search and again perform a repo at the very next level.
Accordingly, if a repo is performed at an immediate parent node,
then bend sequence planner 72 will constrain the placement of a
repo node on OPEN.
[0249] FIGS. 20A and 20B each illustrate a simple example workpiece
16 having two faces 262, and one bend line 260. In addition, each
of FIGS. 20A and 20B includes an accompanying diagram of a node
expansion from the root node n.sub.0 to the first level of a search
tree which includes two expanded nodes. FIG. 20B shows two expanded
nodes, while FIG. 20C shows one expanded node and indicates that
the other node has been constrained. Referring to FIG. 20B, since
only one bend is to be performed an workpiece 16, only two nodes
are shown. The bend may be performed in accordance with node A,
whereby bend 1 is performed with face 2 being inserted into the die
space of the bending workstation, or bend 1 may be performed in
accordance with n.sub.2, whereby bend 1 is performed with face 1
being inserted into the die space. Referring to FIG. 20C, once
workpiece 16 is bent along bend line 260, it is apparent that face
1 will result in a flange having a height which is too small to
allow grasping of workpiece 16 at that side of the workpiece when
performing the bend. Accordingly, in order to perform bend 1 along
bend line 260, workpiece 16 must be grasped by a robot gripper from
the side of workpiece 16 corresponding to face 2. In other words,
bend 1 must be performed with face 1 being inserted into the die
space. Thus, the search tree illustrated in FIG. 20C only-includes
one node n.sub.1, and shows that while the parent node n.sub.0
might normally be expanded to include a second node, the second
node has been constrained.
[0250] A node may be constrained by eliminating it from
consideration as a possible operation within the bend sequence.
Such elimination of a node may be accomplished by preventing an
expansion from including thy node, or by simply failing to place
the node on the OPEN list.
[0251] FIG. 20D illustrates an example workpiece 15 having two
co-linear bends, with bend lines 1 and 2. The nodes that may be
generated from this workpiece include the following: (1,2), (1,1),
(2,2 (2,1), ((12),1), and ((12),2). By convention, the holding
faces are defined an each side of the first bend line of the
co-linear bend. FIG. 20E illustrates another example workpiece 16.
The holding sides for this co-linear bend (bending at lines 1 and 2
simultaneously) are defined in the following twin nodes: ((1 2)1),
((1 2)2). Note that the bend twin holding face is face 1, even
though face 1 also extends to the other side of the bend line
(i.e., even though it extends to a position which would be behind
the die space during a bend). This is because of the convention
noted above, which is used to choose the bend twin holding
face.
[0252] FIG. 21 illustrates, in a simplified flow chart, an example
embodiment of a state-search algorithm, comprising an ordered
search algorithm, based on the algorithm disclosed by Nils J.
Nilsson in "Problem-Solving Methods in Artificial Intelligence",
which may be utilized by the bend sequence planner of the present
invention in order to form a bend sequence to be utilized by a
bending workstation. After the algorithm is started, at step S10, a
start node n.sub.0 is placed on a list called OPEN, and a function
value f is set equal to 0. Thereafter, in step S12, a determination
is made as to whether there is anything in the OPEN list. If the
OPEN list is empty, the process is forwarded to step S14, and an
error indication is given. If the OPEN list is not empty, as
determined at step S12, the process will proceed to step S18.
[0253] At step S18, the nodes placed within the OPEN list are
checked, and the node having the smallest f value is removed from
OPEN and placed on a CLOSED list. This node is called n.sub.i.
Thereafter, in step S20, a determination is made as to whether the
node n.sub.i is a goal node. If it is a goal node, the process is
forwarded to stem 522, where a solution path is generated by
tracing back from node n.sub.i, through its pointer and the
pointers of the previous nodes, to the start node n.sub.0. However,
if node n.sub.i is not the goal node, as determined at step S20,
the process will be forwarded to step S24. In step S24, node
n.sub.i is expanded to generate all of its successor nodes, called
n.sub.j. If there are no successors nodes n.sub.j, the process will
return to step S12. For each successor node n.sub.j that is
generated, a computation will be made for a corresponding f value
f(n.sub.j)=k'(n.sub.j)+h(n.sub.j), where k' is equal to the sum of
the k costs of performing each node from the starting node to the
current node, and h is equal to the projected cost from the current
node to the goal node. Also, in step S24, each of the computed f
values will be associated with their corresponding successor nodes
n.sub.j that are not already on either the OPEN or CLOSED lists.
Such successor nodes n.sub.j are then placed an the OPEN list, and
pointers are directed from those successor nodes n.sub.j back to
n.sub.i. For each successor node n.sub.j that was already on an
OPEN or CLOSED list, an f value is associated with that successor
node n.sub.j that is equal to the smaller of the f value just
computed for that node node and the f value already associated with
that node. The successor nodes n.sub.f on the CLOSED list who have
their associated f values made smaller are placed on the OPEN list,
and the pointers for those successor nodes n.sub.j are redirected
to n.sub.f. After execution of step 24, the process will return to
step S12.
[0254] (c) Illustrated Example Bend Sequence Planner
[0255] FIGS. 22A-22C illustrate a particular example embodiment of
a bend sequence planning process to be performed by bend sequence
planner 72 illustrated in FIG. 5A. The bend sequence planning
process is started upon receipt of a command to commence operation,
e.g. as indicated in Step S26, by proceeding on receipt of an FEL
command to start planning. Once the process starts, and proceeds in
step S28, one or more files corresponding to the parts to be
produced are read by the bend sequence planner. Such files may be
in he forms of a shape file including information such as geometric
and topological information (a 3D data description of the part and
a parallel 2D data description of the part corresponding to 3D data
description) labeled geometric features which are pertinent to
determinations to be made by bend sequence planner and a bend graph
correlating bends to be performed with geometric and topological
information.
[0256] Once the part file has been read in step S28, the process
proceeds the steps S30, S32, and S34, during which each expert is
initialized. More particularly, the holding expert, the tooling
expert and the motion expert are each initialized. Once the various
experts have been initialized, in step S36, a list of bends is
built, and calculations are performed regarding the various
features of the parts. For example, a computation may be performed
regarding what the lengths of bends are and which bends are
co-linear. Thereafter, in step S38, an A* algorithm is initiated,
including steps such as putting a root node r on an OPEN list, and
setting an f value equal to 0. A determination is then made at step
S40 as to whether the OPEN list is empty. If the list is empty, the
process will proceed to step S42, and exit with an error
indication. Otherwise, if the OPEN list is not empty, the process
will proceed to step S44, in which the node on the OPEN list with
the smallest f value will be taken and placed on a CLOSED list. The
chosen node will be called n.sub.i for purposes of explaining the
steps of the flow charts of FIG. 22A-FIG. 22D.
[0257] In step S46, a determination is made as to whether node
n.sub.i is a goal node. If node n.sub.i is a goal node, the process
proceeds to step S48, where a solution path is generated.
Otherwise, if n.sub.i is not a goal node, the process proceeds to
step S50 which is shown at the top of FIG. 22C.
[0258] After generating a solution path in step S48, the process
will proceed to step S56 which is shown at the top of FIG. 22D. In
step S56, a finalize message is sent along with the bend sequence
to each of the experts and each of the experts is queried for final
detailed information which is needed to complete the bend sequence
plan. Thereafter, in step S58, the bend sequence planner will await
a response from the tooling expert. Once all the final information
has been received from the tooling expert, in step S60, the setup
of the bending workstation will be started. In the meantime, while
the setup of the workstation is being performed, in step 362, the
process will await a response from the motion expert and the
holding expert. Once the complete motion expert and holding expert
plans have been received, at step S64, the final plan will be
forwarded to the sequencer of the system.
[0259] Assuming that n.sub.i is not determined in step S46 to be
the goal node, the process will continue at step S50 at the top of
FIG. 22C. At this step, node n.sub.i will be expanded to obtain its
successor nodes n.sub.j. The successor rides will include bend twin
nodes for each bend, i.e., two nodes corresponding to each bend,
and an additional node for a repo, minus any nodes which are
constrained from being successor nodes at the present level of the
search.
[0260] Once the successor nodes have been generated in step S50, a
subplanning and cost assignment process is performed in step S52.
Thereafter, in step S54, successors n.sub.j are each placed on the
OPEN list, with the subplan information and cost information
corresponding to each node being associated with each node in the
OPEN list (e.g., by using pointers). The process will then return
to step S40 where a determination will be made as to whether the
OPEN list is empty. If the OPEN list is empty, the process will
exit with an error indication at step S42; otherwise the process
will proceed to again execute steps S44, S46, S48, S50, 552 and
S54.
[0261] FIGS. 23A-23D illustrate the subplanning and cost assignment
process which corresponds to step S52 in the bending sequence
planning process illustrated in FIGS. 22A-22D. The subplanning and
cost assignment process determines or formulates a subplan and
incremental costs which correspond to each of the
expanded/successor nodes n.sub.j which have not been eliminated as
a viable node at the present level of the search due to
constraints. For each such expanded/successor node, the process
illustrated in FIGS. 23A-23D will be performed. In a first step
S66, a test will be performed for the permutability of node n.sub.j
regarding the subplan and costs of the holding expert. More
particularly, a test will be performed to determine whether the
subplan and costs which will be determined by the holding expert
will be the same as that already determined for another
"equivalent" node if such is the case, the subplan and costs will
be identical to that "equivalent" node, and it is unnecessary to
again query the holding expert for such information which would
result in an unneeded use of time. If it is determined at step S68
that an equivalent node was found, then the process proceeds to
step S70, where the subplan and costs are copied and associated
with that successor node n. However, if an equivalent node is not
found in step S63, the process proceeds to step S72, where the bend
sequence planner will query the holding expert for a proposed
subplan, the incremental k cost, and the incremental h cost. In
performing step S72, as soon as a cost of infinity has been
evaluated by the holding expert, the present successor node n.sub.j
will be aborted. Thus, the successor node n.sub.j will be discarded
at the present level of the search, and the subplanning and cost
assignment process will again start with the next available
successor node n.sub.j.
[0262] Once the subplan and costs have been obtained either by step
S70 or step S72, the process will proceed to step S76 (at the top
of FIG. 23B), where another test far permutability will be
performed regarding the tooling expert subplan and costs. If an
equivalent node is found, as determined at step S78, the bend
sequence planner will copy the subplan and costs corresponding to
the equivalent node and associate the same with the present
successor node n.sub.j. In the alternative, if an equivalent node
is not found, the process will proceed to step S82 where the
tooling expert will be queried for a proposed subplan, a k cost and
an h cost. If a cost of infinity is evaluated, the present
successor node will be aborted at step S84. Once the proposed
subplan and costs have been determined, the process will proceed to
step S36, where the bend sequence planner will await the results
from the holding expert and the tooling exert. The process will
wait far the results of the holding expert and tooling expert
queries, since such information is needed by the motion expert to
do its subplanning and cost assignment computations.
[0263] In step S88, a test will be performed for the permutability
regarding the motion expert subplan and costs. That is, a test will
be performed to determine if the subplan and costs that would be
assigned by the motion expert are identical to those which have
already been assigned to another node, the other node thereby being
deemed an "equivalent" node to the present successor node n.sub.j
being evaluated. If, at step S90, it is determined that an
equivalent node has been found, the process will proceed to step
S92, where the subplan and costs of the equivalent node will be
copied and thereby associated with the present successor node
n.sub.j. However, if an equivalent node is not found, the process
will proceed to step S94, where the motion expert will be queried
for a proposed subplan, a k cost and an h cost. If any of the costs
are infinity, the present successor node will be aborted,
proceeding to a next successor node and again commencing
subplanning and cost assignment for the next successor node.
Assuming that the proposed subplan and costs have been obtained the
process will process to step S98, where the results will be awaited
from the motion expert. Additional processing may be performed to
obtain a subplan and costs regarding different aspects of the
system which will be related to performance of the overall bend
sequence proposed by the bend sequence planner. In this regard,
additional experts may be provided as indicated by the reference
numeral S100. For example, FIG. 5A shows a sensing expert. The
subplanning and cost assignment process could be appropriately
modified to include steps such as testing for permutability,
querying the additional expert (e.g., sensing expert) for a
proposed subplan and costs, and, at an appropriate location within
the process, awaiting the results from the additional expert.
[0264] Once the results from the motion experts have been obtained,
as determined at step S98, the process will proceed to step S102
which is shown at the top of FIG. 23D. In step S102 the f value for
node n.sub.j will be calculated in accordance with the formula:
f.sub.nj=(k'+h).sub.HE+(k'+h).sub.TE+(k'+h).sub.ME. Then, in step
S104, the f value will be adjusted based upon any heuristics which
pertain to the successor node n.sub.j. In this regard, if it is a
desired node, i.e., it has beneficial or desired heuristics which
say that this node is preferable over other nodes, a value will be
added to the f value. However, if the node is undesired, a value
with be subtracted from the f value.
[0265] FIG. 24 illustrates an example flat workpiece 16, and
several nodes expanded during the performance of a state-space
search by the bend sequence planner illustrated herein. Various
costs are shown which are assigned to the nodes throughout the
search process. As shown, flat workpiece 16 has two portions a, b
which are to be bent to form flanges. First flange a is placed in
between two tabs c, d. First flange a is to be bent along bend line
1, and second flange b is to be bent along bend line 2. The first
node n.sub.0, i.e., the root node, of the search tree corresponds
to flat workpiece 16. Successor nodes of node n.sub.0 include nodes
n.sub.1 and n.sub.2, which correspond, respectively, to bend lines
1 and 2. In the illustrated example, it is assumed that a bend
along bend line 1 would be performed with flange a inserted into
the die space of the bend press, and that a bend along bend line 2
would be performed with flange b inserted into the die space. Thus,
there are no bend twins illustrated in the tree of FIG. 24. There
is only one node per bend line.
[0266] In the event that the bend sequence planner is designed to
assign bend twin nodes for each bend, the alternate node would
likely be constrained in the present example. For example, it would
likely not be possible to perform a bend along bend line 1 by
inserting flange b into the bend press, since flange a is very
short, and thus cannot be grasped by a robot gripper during
execution of the bend.
[0267] At the first level of the search, two successor modes and
n.sub.2 are generated as successor nodes. In forming these two
nodes, the bend sequence planner may ask each of the holding
expert, tooling expert, and motion expert for the incremental cost
(i.e., h and k costs) corresponding to that made. For example, the
costs that are assigned to node n.sub.1 are illustrated in the box
corresponding thereto as, shown in FIG. 24. A holding expert
assigned a k cost (i.e., the cost that it takes to move from the
parent node n.sub.0 to the present node) of 0. This signifies that
a grip location can easily be found an workpiece 16, and that there
is need to reposition the grip of the robot an the workpiece before
performing bend 1 as a first bend in the bend sequence. The holding
expert further assigned an h cost of 30. The number 30 represents
an approximate amount of time (30 seconds) which it will take to
reposition the gripper's grasp an the workpiece 16 (i.e., to
perform a repo). This value represents that the holding expert has
predicted that one repo will be needed in order to complete the
bend sequence associated with workpiece 16. The h cost is a
predicted cost to complete the bend sequence from the present node
4 to the final goal node.
[0268] The costs assigned by the tooling expert include a k cost of
600 and an h cost of 600. The k cost is the incremental amount of
time (due to tooling) associated with performing the bend of that
node. In this case, in order to perform the bend of bend line 1, a
first stage must be placed an the die rail of the bending
workstation. An approximated time for installing the first stage is
600. Accordingly, the incremental k cost (for tooling) from n.sub.0
to n.sub.1 is 600 seconds. The predicted additional cost from node
n.sub.1 to the goal node (i.e., the h cost for tooling) is
calculated to be the time needed to install one additional stage,
and thus is 600 seconds.
[0269] The costs assigned by the motion expert include an
incremental k cost of 5 (an estimated 5 seconds), equal to an
approximated robot travel time in moving from n.sub.0 to node
n.sub.1. The costs assigned by the motion expert further include a
predicted future h cost of 15 seconds, which is equal to a running
average of all k costs evaluated so far (since n.sub.0) multiplied
by a summation of the number of remaining bends and twice the
number of predicted repos: h=k.sub.AVE [number of remaining
bends+(number predicted repos) (2)]. The nether of predicted repos
is multiplied by 2, since two movements are required per
repositioning. One movement is required to take the robot from a
present stage to the repo gripper, and a second movement is
required to reposition the robot gripper's hold on the part. The k
value for the next node is calculated based upon the amount of time
that it takes to move from the repo gripper to the appropriate
stage for the next bend.
[0270] The alternate node at the first level of the search is node
n.sub.2. This node corresponds to bend line 2. The incremental
costs include k and h costs assigned by the holding expert, k and h
costs assigned by the tooling expert, and k and h costs assigned by
the motion expert. The k and h costs assigned by the holding expert
are 0 and 30 respectively. The holding expert assigns a k cast of
0, because no repositioning is necessary to go from node n.sub.0 to
node n.sub.2. However, a holding h cost of 30 is assigned because
one repo is predicted to be necessary in order to complete all of
the bends of the bend sequence, i.e., to get to the goal node. This
becomes apparent when viewing workpiece 16. Depending an which bend
is done first, since the bends are on opposite sides of the
workpiece 16, it will be necessary to reposition the robot's grasp
an workpiece to be at the other side of workpiece 16 in order to
perform the other bend. Further, since the workpiece is somewhat
arrow, it would not be possible to locate the robot gripper at
either the left or right sides of workpiece 16 so that the
workpiece can be grasped at the same location for both bends. If
the robot gripper was positioned at one of the sides of workpiece
16, robot gripper would likely collide with the tooling (the punch
tool) of the bend press when the die is raised to perform the
bend.
[0271] The k cost assigned by the tooling expert again is 600,
since the bend, being the first bend introduced in the search, will
require at least one stage. 600 seconds is an approximated time for
installing a stage, and thus is assigned as the incremental k cost
to go from node n.sub.0 to node n.sub.2. The h cost assigned by the
tooling expert is 600, since a predicted additional stage will be
necessary to go from node n.sub.2 to the goal node. The motion
expert assigns a k cost of 4, and an estimated h (future) motion
cost of 12. The k cost assigned by the motion expert for node
n.sub.2 is less than the k cost assigned for node n.sub.1. This is
because bend line 2 is longer than bend line 1, and thus requires a
larger stage. In a typical bending workstation, such as the Amada
EM100 workstation illustration in FIG. 1, it is preferred that
longer stages be placed in the center of the die rail, and that
shorter stages be placed off to the sides. Thus, to go from an
initial position before any bends are performed (at node n.sub.0)
to a center stage would require less movement by the robot than
moving to a stage set off to the side of the die rail. Accordingly,
the calculated robot travel time, without regard to the collisions,
from the loader/unloader (L/UL) to the center stage in performing
bend 2 is estimated to be 4 seconds, and less that it would take to
get a stage positioned at the left side of the die rail which is
where the smaller stage would be placed along the die rail. Since
the h cost is calculated as a function of the present ruing average
of the k cost calculated so far, the h cost is also a lower value
of 12 seconds.
[0272] At the first level of the search, the respective total
incremental costs performing bends 1 and 2, respectively, are 1250
and 1246. Accordingly, node n.sub.1 has a total incremental cost of
1250, and node n.sub.2 has a total incremental cost of 1246, the
total cost being assigned by each of the experts queried by the
bend sequence planner.
[0273] It is noted that the only two nodes at the first level of
the search included a node for performing bend 1, and a node for
performing bend 2 (nodes n.sub.1 and n.sub.2). The first level did
not include a node for performing a repo. This is because the
search is constrained so that the first bend to be performed at the
first level after the root node does not include a repo. It would
be unnecessary for a repo to be performed as a first step in the
bend sequence, since the robot gripper can be placed anywhere at
the start to correspond to any particular bend. However, at the
next level of the search, a repo is included as a possible node, in
addition to the one or more bends which comprise the rest of the
bends leading to the goal node. Accordingly, the next level of the
search includes nodes n.sub.0) which corresponds to bend 1, and
n.sub.4 which corresponds to a repo before performing the next bend
in the bend sequence. At node n.sub.3, upon being queried by the
bend sequences planner, the holding expert assigns a cost of
infinity, since there are no available grasp regions that were used
in performing bend 2 that can also be used to perform bend 1. If
there was a grass region that was used in order to perform bend 2
that could also be used to perform bend 1, then the robot gripper
could be placed within that intersecting region, and the
repositioning of the gripper would not be necessary when going from
the completed bend 2 to bend 1 (i.e., from node n.sub.2 to node
n.sub.1). However, in this, case, the holding expert has determined
that there is no such intersection of grasp regions, and thus the
incremental k cost for holding is infinity. The predicted h cost is
not even relevant, nor are any of the other costs which might be
assigned by the other experts such as the tooling expert and the
motion expert, since bend 1 cannot be performed at the present
point in the bend sequence, without first performing a repo. Thus,
node n.sub.3 is no longer considered, and the bend sequence planner
proceeds to the repo node n.sub.4, and queries the respective
experts for their assigned costs associated with that node.
[0274] After repo node n.sub.4, the holding expert assigns a k cost
of 30, which signifies that approximately 30 seconds will be needed
to perform a repo at the present point in the bend sequence. A
predicted h cost of 0 is assigned by the holding expert, since it
is predicted that no additional repos will be needed between the
present node n.sub.4 to the goal nodes. After the holding expert
assigns its cost, the tooling expert, upon being queried by the
bend sequence planner, assigns a k cost of 600, which equals the
approximate time (600 seconds) to install an additional stage which
will be needed in order to perform bend 1 (along bend Line 1),
since the stage which was utilized to perform bend 2 (which has a
length equal to the length of bend line 2) cannot be used to
perform bend 1 since such a stage cannot fit between tab portions c
and d of workpiece 16. No additional predicted stages or tooling
change is expected by the tooling expert; and accordingly, the
tooling expert assigns an h cost of 0 to be associated with node
n.sub.4. It is noted that the tooling expert may initially
determine a total initial h cost based upon the total amount of
predicted stages that will be needed to perform the complete bend
sequence, either at an initial point in the search before
performing the search. ID the present example, a total initial h
cost is calculated to be 1200, since two predicted stages have been
predicted to be necessary to perform bends 1 and 2 on workpiece 16.
Throughout the search, the k cost is either 0 (with no extra stages
needed) or 600 (if an additional stage is needed for the bend
corresponding to the present node). The b cost for a given node is
equal to the total initial h cost minus all of the preceding and
current k costs leading up to and including the given node.
Accordingly, for node n.sub.4, since the preceding k cost leading
to n.sub.4 was 600, and the present k cast for n.sub.4 is 600, he h
cost is 1200-600-600=0.
[0275] The cost assigned by the motion expert to correspond to node
n.sub.4 include a k cost of 8 and an h cost of 4. The k cost is
estimated to be twice the average preceding k cost, since two
motions are needed in order to perform a repo. One movement is
needed to take the workpiece from a stage at which the workpiece
was left from a previous bend to the repo gripper, and the second
movement is to move the robot gripper to the repositioned location
while the repo gripper is grasping workpiece 16. The predicted h
cost assigned by the motion expert for a repo node is the predicted
additional costs needed to perform all future movements in the bend
sequence. In this case, h is estimated to be the h value calculated
for a previous node n.sub.2 minus the present k cost, and thus is
estimated to be 4 seconds for node n.sub.4. The total incremental
costs are then added to the total of all previous k costs preceding
that node (in this case repo node n.sub.4). Thus, all the
incremental associated with node n.sub.4 are added to a total
previous k costs of 604 which were previously calculated in
association with node n.sub.2, to obtain a total cost value of
1246.
[0276] The bend sequence planner will, in performing its
state-space search, thus choose n.sub.4 as the best node and will
proceed with expanding that node to form its successor nodes. The
successor nodes of repo node n.sub.4 include node n.sub.5. In this
case, node n.sub.5 is the goal node, since it results in the
workpiece 16 having all of its bends completed to form a 3D part.
The costs determined by the relative experts include a presumed
holding k cost of 0, a calculated tooling k cost of 600, and a
calculated motion k cost of 4. Since the present node n is known to
be the goal node, no h costs are calculated. The previous total k
costs 642 seconds. Accordingly, 642 is added to the k cost for
tooling of 600 and the k cost for motion of 4 to be equal a total f
value of 1246. Such an f value is the cheapest f value among the
nodes still left on OPEN. Accordingly, this node will be checked to
see is it is a goal node, and if it is a goal node, the solution
path will be generated to include (in order) bend 2 which
corresponds to node n.sub.2, a repo which corresponds to node
n.sub.4, and bend 1 which corresponds to node n.sub.5.
[0277] (d) Permutability Determination
[0278] As described above, in connection with FIGS. 23A-23D, before
asking an expert for the costs associated with a particular node, a
test is performed for the permutability of that node regarding the
subplan and costs for each expert. For example, in step S66 shown
at the top of FIG. 23A, a test is performed for the permutability
of a particular successor node n.sub.j to determine if it is merely
a permutation of another node, and thus has an equivalent set of
subplan and costs if this is the case, it would be wasteful to
again ask the holding expert for a proposed subplan and associated
k and t costs, since these parameters are already known, and can be
obtained by merely referring to the other equivalent nodes. FIG. 28
illustrates a graph of compared histories of nodes b6' and b6,
which have been generated by the bend sequence planner in
performing its state-space search. Assuming that the subplanning
and cost assignment process of the bend sequence planning algorithm
was being performed on a particular node b6, at each of steps S66
(FIG. 23A), S76 (FIG. 23B), and S88 (FIG. 23C), a test will be
performed for the permutability of that node with any other nodes
in the search tree regarding the holding expert's subplan and
costs, the tooling expert's subplan and costs and the motion
expert's subplan and costs, respectively. In testing whether or not
a node is a mere permutation of another node within the search
tree, a node such as node b6 illustrated in FIG. 23 will be
compared to another node in the search tree, such as node b6', also
illustrated in FIG. 28. In making the comparison, the history of
node b6, which includes nodes b2, r1, b4, b3, r2, and b5, is
compared to the history of b6', which includes b2', r1', b2', b4',
r2' and b5'.
[0279] Depending on the particular implementation of the bend
sequence planner and the particular calculations made by each of
the experts, the method to be used to determine whether one node is
a permutation of another will vary. However, an analysis can be
performed of the various permutations of nodes, and the various
subplans and costs that can be associated with each node at various
levels of the search, in order to determine under what conditions a
node is a mere permutation of another node in the search. Based
upon the results of the analysis, an appropriate method may be
formed for determining whether a node is a permutation of another
node, in terms of the subplan and costs assigned for the node.
Thus, while the above-described examples have been given for
determining the permutability or a node regarding the subplan and
costs assigned by the holding pert and the motion expert,
respectively, alternative methods may be used depending upon
particular variations and implementations of the bend sequence
planner and the experts of a system. A similar method can be
provided for determining whether or not a node is permutable with
another node in terms of the subplan and costs assigned by a motion
expert. Thus, a specific embodiment for making that determination
is not described in detail herein.
[0280] 3. Expert Modules, Subplanning, and Dialogue Between
Modules
[0281] FIGS. 29-31 respectively include charts which depict he
dialogue between the bend sequence planner and the holding expert,
tooling expert, and motion expert of the illustrated embodiment
planning system 71 as shown in FIG. 5A Referring to FIG. 29, which
illustrates the dialogue between bend sequence planner 72 and
holding expert 82, several query arrows Q1, Q2, Q3, Q4 and Q5 are
illustrated to represent a query message being forwarded from the
bend sequence planner 72 to holding expert 82. In addition, several
response arrows R1, R2, R3, R4, and R5 are illustrated to represent
response messages from holding expert 82 to bend sequence planner
72. While the queries and responses are indicated in FIG. 29 with
consecutive numbers from 1 to 5, this is not meant to indicate that
there could not be additional queries and responses, in between,
before, or after the queries and responses illustrated in FIG. 29.
Rather, these numerals are merely provided to facilitate the
description of the dialogue between the modules as shown in FIG.
29.
[0282] At some point before commencing its search (e.g., at step
S30 as illustrated in FIG. 22A), bend sequence planner 72 forwards
an initial query Q1 to holding expert 82, which includes, among
other things, a start command, and a file name for the part to be
produced. This query Q1 could be forwarded utilizing a VERB "plan .
. . " (which is utilized to initialize a module for planning a
part). Upon receipt of query Q1, the holding expert then performs
an input operation indicated by I1, which includes reading an
appropriate file which includes geometric, topological, feature
information, and other information regarding the parts to be
produced. After the part is read, initial planning steps will be
performed, as indicated in block P1. More particularly, holding
expert 82 will perform gripper selection, which includes picking a
robot gripper, and which includes picking a temporary repo gripper.
In addition, holding expert 82 will predict the minimum number of
repos that will be needed to complete the overall bend sequence.
After performance of the initial planning steps in P1, holding
export 82 then sends the resulting information back to bend
sequence planner 72 via a response R1. The response includes a
savelist which includes a list of names of attributes to he saved
by bend sequence planner 72. The savelist further includes, along
with each attribute name, the parameters and values accompanying
each attribute to be saved by bend sequence planner 72. The
attributes to be saved by bend sequence planner 72 at this paint
include the selected robot gripper, the temporarily selected repo
gripper, and the values indicative of the m predicted number of
repos which will be necessary to complete all of the bends of the
bend sequence.
[0283] After response R1 (egg., in step S38 of the bend sequence
planning process illustrated in FIG. 22B), the search is started.
After commencing the search, a query Q2 is sent to holding expert
82 (e.g., at step S72 of the bend sequence planning process
illustrated in FIG. 23A). The query Q2 includes bend sequence
information, and a request for a proposed subplan, a k cost and an
h cost associated with that particular node. In this regard, a
"get" FEL command may be utilized to perform this query. After
receipt of query, Q2, holding expert 82 will then perform planning
steps indicated in block P2, which include predicting the number of
repos which will be needed after performance of the presently
proposed bend-related operation, determining the grasp location
(i.e., the location at which the robot should grasp a workpiece in
order to perform the presently proposed bend), and potential repo
locations (for the repo gripper's grasp on the workpiece), and will
also determine k and h costs associated with the particular
proposed bend-related operation (which would include either a bend
or a repo). Once all the planning is performed in block P2, holding
expert 82 will then respond with a response R2 to bend sequence
planner 72, the response including the k and h costs, a subplan,
and various attributes which will be saved by bend sequence planner
72 as specified in a savelist forwarded by holding expert to bend
sequence planner 72. If the presently proposed node is not a repo
node, k will either be equal to 0 or infinity, 0 indicating that no
repo is necessary at the present node, and infinity indicating that
there are no available places for the robot to grasp the workpiece
without first performing a repo. The h value will be equal to 30
(an estimated amount of time it takes to perform a repo) times the
predicted number of repos from the present node to the goal nodes.
If the present node is a repo node, k will be equal to 30, if the
repo is possible, or infinity if a repo cannot be performed at the
present level of the search for the present node. The h cost will
be 30 times the predicted number of repos which will need to be
performed after performance of the present node bend-related
operation.
[0284] After performance of processing in relation to query Q2 and
response R2, bend sequence planner 72 will then very various other
exerts including tooling expert 80 and motion expert 84, in order
to obtain their respective subplans and costs, and repeatedly will
query each of the experts in association with each node generated
during the search in order to form a complete bend sequence plan
which includes nodes from the start node to the goal node. Once the
search has ended and a solution has been obtained, bend sequence
planner 72 will forward another query Q3 to holding expert 82 which
includes a request for the suction cup plan, again utilizing the
"get" verb of EEL. In reasons to query Q3, holding expert 82 will
perform suction cup planning as indicated by block P3. Suction cup
planning will include a determination of what locations along the
workpiece loader/unloader may place its suction cups during loading
and unloading of the workstation. Once the suction cup planning has
been completed, holding expert 82 will pond with response R3 to
bend sequence planner 72. Bend sequence planner 72 will
subsequently again query, by query Q4, holding expert 82, for the
final repo gripper that will be used and the location of the repo
gripper on the workpiece for various stages of the bend sequence.
The "get" verb of FEL may be used for this query. After receipt of
query Q4, holding expert 82 will perform the planning indicated in
block P4, which includes repo planning to be performed after the
searched. In performing the repo planning after the search, holding
expert 82 chooses a true repo gripper to be utilized in execution
of the resulting bend sequence plan, and finalizes the repo
position based upon the chosen repo gripper. After completion of
the repo plan after the search, holding expert 82 will forward a
response R4 to bend sequence planner 72. Thereafter, in query Q5,
bend sequence planner 72 will further query holding expert 82 for a
backgage plan. Accordingly, holding expert 82 will perform backgage
planning as indicated by block P5, and will respond to bend
sequence planner 72 with the appropriate backgage plan in response
R5.
[0285] Once all the planning has been performed by holding expert
82, including the final planning after the search, bend sequence
planner 72 will have queried the motion expert 84 for its final
plan information, and will await, before execution of the plan, the
results of the final motion plan from motion expert 84. After
receipt of the final motion plan from motion expert 84, bend
sequence planner 82 will then proceed to forward the final plan to
sequencer 76.
[0286] In the illustrated dialogue between bend sequence planner 72
and tooling expert 80 in FIG. 30, several queries are illustrated
from bend sequencer planner 72, indicated by query lines Q11, Q12,
and Q13, and several responses are illustrated by response line
R31, R12, and R13. As indicated by the first query line Q11, at
some point in time before commencing its search (e.g., at step S32
in the bend sequence planning process illustrated in FIG. 22A),
bend sequence planner 72 will command tooling expert 80 to start
its processing, and will forward the name of the part to be
produced with the use of a "plan" verb in FEL. Upon receipt of
query Q1, as indicated by input line I2, tooling expert 80 will
then read an appropriate part file. Subsequently, tooling expert 80
will perform various planning steps as indicated by blacks P11, P12
and P13. These planning steps include selection of a tool profile,
bin-packing, and performing a calculation of an initial h value
(which corresponds to the total number of predicted stages that
will be needed to perform all of the bends of the bend sequence).
The bin-packing algorithm comprises the selection of tool segments
that will together add up to the appropriate stage length far each
stage to he utilized by the bending workstation in performing the
bends of the bend sequence. Once all of the appropriate plan
information is gathered in planning blocks P11, P12, and P13,
tooling expert 80 will respond as indicated by response line R11,
to bend sequence planner 72, and will indicate to bend sequence
planner 72, via a savelist, various attributes to be saved.
Subsequently (e.g., at step S38 in FIG. 22B), the bend sequence
planner 72 will commence it search. Once the search is commenced
and after the information has been gathered form holding expert 82,
bend sequence planner 72 forward a query Q12 to tooling expert 80,
which includes the bend sequence at that point of the search and a
query far the subplan and associated k and h cosmos. The verb "get"
in FEL is utilized for this query. Tooling expert so then performs
planning steps, as indicated by planning block P14, which include
picking of a stage length to correspond to a bend and a location
along that stage where the bend should be performed, arranging the
stages, calculating the k and h costs, and performing fine motion
planning. Then, tooling expert 80 responds to bend sequence planner
72 via response R12, and forwards the k and h costs and the
associated subplan information to bend sequence planner 72. A
savelist is also included in response R12 which indicates
information and attributes that should be saved by the planner.
Subsequent queries and responses may be exchanged throughout the
search, with tooling expert 80 and with other experts 82 and 84
before the search is finished. Once the search ends and a solution
has been found (e.g., in step S56 in FIG. 22D of the bend sequence
planning process), a query Q13 instructing the tooling experts to
finalize will be forwarded to tooling expert 80. Tooling expert 80
will then perform its appropriate final processing, and return, via
response R13, any final information to bend sequence planner 72.
Subsequently bend sequence planner 72 requests final information
and final processing to be performed by motion expert 84 and will
await the results thereof. Once the final motion planning results
have been obtained by motion expert 84, bend sequence planner 72
will compile all information to form a final plan, and will forward
the same to sequencer 76.
[0287] As illustrated in FIG. 31, bend sequence planner 72
communicates with motion expert 84 before during and after
performing a search, in the form of queries and responses which may
include the queries indicated by query lines Q21, Q22 and Q23, and
respective response lines R21, R22 and R23. Initially (e.g., as
indicated at step S34 in FIG. 22A), a first query Q21 may be
forwarded to motion expert 84 which includes a start command, and
the name of the part to be produced. Upon receipt of query Q21,
motion expert 84 will then input the appropriate part file and a
channel file which represents all of the free space channels
through which the part and the robot may be manipulated in
performance of the various bends and operations of the bend
sequence. This input is indicated by I3. Thereafter, motion expert
84 will send a response R21 to bend sequence planner 72,
indicating, essentially, that the information was read in and
acknowledging that it is ready for the next query by bend sequence
planner 72. Sometime thereafter (e.g., at step S38 in FIG. 22B),
the state-space search of the bend sequence planner 72 will
commence. Then, bend sequence planner 72 will query holding expert
82 for various information while performing the first level of the
search, then query tooling expert 80, and thereafter send a query
Q22 to motion expert 84. Query Q22 includes information about the
bend sequence, the gripper location and the bend locations an the
stages (in the form of a bend map). This query may be sent to
motion expert 84 by using "get" verb in FEL. Upon receipt of query
Q22, motion expert 84 will perform processing in processing black
P21, and thus will develop a subplan and determine the k and h
costs for performing the bend proposed by bend sequence planner 72
at that particular point in the bend sequence. The resulting k and
h costs and subplan are returned to bend sequence planner in
response R22. Afterward, additional processing by other experts 80,
82, and by motion expert 84 may be performed in order to complete
the search.
[0288] Once the search has ended and the solution has been
obtained, bend sequence planner 72 will send an additional query
Q23, which includes a finalize command. With query Q23, bend
sequence planner 72 will forward information to motion expert 84 so
that motion expert 84 may perform all final planning operations.
Such forwarded information would include the bend sequence, the
gripper locations for each bend in the sequence, the repo locations
for each repo to be performed, the bend maps corresponding to the
bends of the bend sequence, and all fine motion plans which have
been developed by tooling expert 80, in order to bring the
workpiece into and cut at the die space when performing each bend
in the bend sequence. Motion expert 84 utilizes that information to
perform the processing indicated in processing block P22. More
particularly, motion expert 84 will figure out the various starting
and finishing paints in order to develop a gross motion plan. A
search algorithm is then performed in order to form paths between
the gross motion starting and finishing locations. Then, the
resulting gross motion paths are linked with the fine motion paths
so that a complete motion scheme is formed, commencing with
acquiring the workpiece from the loader/unloader during loading at
the workstation, bringing the workpiece to each of its bends, and
finally bringing the finished workpiece to the loader/unloader to
be unloaded from the workstation.
[0289] The complete motion plan is then returned to bend sequence
planner 72 in a response R23. Once the complete motion plan has
been received by bend sequence planner 72, bend sequence planner 72
may compile the complete plan, and forward the same to sequencer 76
for execution.
[0290] FIG. 32 illustrates a flow chart of an example process for
performing robot gripper selection. This process is performed,
e.g., in planning block P1 in FIG. 29. In a first step S128, a
library of grippers is read in. Then, in step S130, the process
prunes obviously bad grippers, e.g., if they have certain
dimensions which are inappropriate for the type of work being
performed by the bending workstation. In step S132, a minimum
number of repos for each gripper is predicted. Thereafter, in step
S134, the one or more grippers having the smallest predicted number
of repos is selected. Then, in step S136, among the selected
grippers, all of the grippers having the largest width are
selected. Among the remaining grippers, those with the smallest
length form the tool center point to the front tip of the gripper,
are selected. Among those selected grippers, the grippers with the
shortest knuckle height are selected. If there is only one gripper
having the largest width among the selected grippers, then that
gripper will be selected and no further determination is needed as
to the length of the gripper or as to the knuckle height of the
gripper. Similarly, if several grippers have the largest width
among the select grippers, but only one gripper has the smallest
length, then that gripper will be selected and no further
determination will be needed as to the knuckle height of the
gripper. If there are several grippers left that have an equal
shortest knuckle height, as determined in step S136, then any one
of those grippers may be chosen. Thereafter, in step S138, the
chosen gripper is returned to the holding expert.
[0291] As illustrated in FIG. 22, a prediction must be made as to
the minimum number of repos needed for each gripper in step S132.
Such a prediction of the minimum number of repos, before the
search, a be performed by utilizing the exemplary process
illustrated in FIG. 34A. The goal of the process depicted in FIG.
34A is to, for a given robot gripper and a given part, predict the
minimum number of repos that will be needed in order to form the
complete 3D part. Among the information utilized. In order to
perform form the prediction, information is needed regarding both
the 2D part, and 3D part (the completely formed bent part). In a
first step, discrete points are generated around a periphery of a
part of a 2D representation of the part. Such discrete points,
located a set distance from the edge of the part, are illustrated
in FIG. 33A. The granularity shown in FIG. 33A is merely for the
purpose of explanation of the algorithm, and does not necessarily
reflect a preferred granularity. The granularity of the discrete
points may be tied in order to obtain an optimum accuracy, while
not sacrificing the speed of the search process.
[0292] Assuming a grasp position at a first one of the discrete
points, a bend set including all of the possible bends for that
robot grasp position will be identified in step S142, assuming that
the part is still flat, (in 2D) and that the part is at the L/UL.
This is repeated for each discrete point around the periphery of
the 2D part 16a (e.g., as shown in FIG. 33A), and all bend sets for
each corresponding robot grasp point are identified.
[0293] Thereafter, in step S144, a determination is made as to the
minimum number of unions of the bend sets determined in step S142
that will form a complete set of bends (i.e., all of the bends of
the bend sequence). This minimum number of unions will be
identified as a 2D minimum number of repos R2. Thereafter, in step
S146, the discrete points are generated around the periphery of a
3D part 16h (e.g., as shown in FIG. 33B). It is noted that the
granularity shown in FIG. 33B is only shown by way of example, and
does not necessarily represent the preferred granularity for
performing the present algorithm. The appropriate granularity for
the generation of points around the outer periphery of the part may
be modified in accordance with the desired accuracy and speed of
the algorithm. For each point generated around the periphery of 3D
part 16b, the corresponding bend set (i.e., all of the possible
bends that may be performed when the robot is grasping the part at
that location) is identified, thereby identifying all of the, bend
sets for all of the discrete points around a periphery of 3D part
16b. Then, proceeding to step S150 (in FIG. 34B), the minimum
number of unions required to get a complete set of bends (i.e., all
of the bends of the bend sequence) is determined, and is called R3
which represents the minimum number of 3D repos. In performing step
S148, all of the possible sets of bends in grasping at the
respective discretized X positions an 3D part 16b are formed
assuming a particular gripper, and further assuming that the 3D
part is located at the repo station. At step S152, the values R2
and R3 are returned to the algorithm for selecting the robot
gripper (e.g., as disclosed in FIG. 32) and to the holding expert.
The value R3 represents an upper bound number of predicted repos,
since it is more difficult to hold the workpiece when it is
completely bent, i.e., a 3D part, than it is to hold the workpiece
in performing bends when it is a flat part. The value R2 represents
a lower bound number of predicted repos. The selection of robot
gripper algorithm and the holding expert may each utilize either
the lower value R2, the upper value R3, or a combination of the two
in performing their calculations and determinations. For example,
for purposes of choosing a robot gripper (in step S134 shown in
FIG. 32), the lower number R2 may be first considered. IF there are
more than one grippers with an, equal smallest predicted number of
repos R2, but with different values R3, then the grippers with the
smallest value R3 may be selected. These selected grippers, if more
than one, would then be further evaluated in accordance with step
S136, as shown in the flow chart of FIG. 32.
[0294] FIG. 35A illustrates a process for predicting the minimum
number of repos which can be used during the search. The algorithm
for predicting the minimum number of repos used before the search
did not include an evaluation of intermediate pats, in order to
save time. In order to have better accuracy throughout the search,
the algorithm depicted in FIG. 35A also considers a formed
intermediate part, and the variations of the part as it moves
throughout the various bends.
[0295] In a first step S154, an intermediate part is formed, by
calling an appropriate function in a geometric modeling library.
The intermediate part includes all of the bends in the bend
sequence so far up to the present node of the search. Thereafter,
in step S156, discrete points are generated around the periphery of
the intermediate part, in a manner similar to that described in the
process of FIGS. 34A-34B, and in a manner similar to that
illustrated in FIGS. 33A and 33B. Once the discrete points are
generated, in step S158, a bend set is determined for each grasp
location point. In other words, a determination is made as to all
of the possible bends that may be performed while the robot gripper
is grasping the part at each discretized point. In step S160, a
determination is made as to the minimum number of unions of the
bend sets generated in step S158 needed to form a complete set of
bends (i.e., all of the bends of the bend sequence). This number is
called Ri. Once the value Ri is determined, then, in step S162,
discrete points are generated around the periphery of the 3D cart.
A bend set (i.e., the possible bends that may be performed for each
gripper position along the discretized points) is then identified
in step S164. The minimum nether of unions of the bend sets is then
determined which would be necessary to form a complete set of bends
(i.e., all of the bends of the bend sequence). That minimum number
of unions is referred to as R3 Then, in step S168, a low h cost
Ri(c) and a high h cost R3 (c) are assigned and returned to the
planner. The cost values Ri(c) and R3(c) are estimates of the
amount of time it takes to perform a repo times the minimum number
of repos (Ri and R3 respectively). Instead of sending the low h
cost and high h cast as noted in step S168 to the holding expert,
the process for predicting the minimum number of repos during the
search may send the values Ri and R3 themselves.
[0296] FIG. 36A illustrates an example process for determining the
robot rasp locations, as performed in planning block P2 in the
chart depicted in FIG. 29 by holding expert 82. In a first step,
S170, an intermediate part (having the bends corresponding to the
present node of the state-space search of the bend sequence
planner) is constructed. Thereafter, in step S172, all edges which
are not appropriate for grasping are rejected. For example, an edge
may be rejected if it is not a face which is parallel to the
robot's XY plane. In addition, an edge may be rejected if it is
inaccessible by the robot gripper when the part is loaded in the
die space. In addition, the edge may be rejected if the edge is too
close to the die, so that the robot would collide with the tooling
before and/or during the bend operation. The edge may also be
rejected if grasping the workpiece on such an edge would cause the
robot to be outside of its work space.
[0297] For each non-rejected edge, the steps following step S172
are performed (shown in FIG. 36A). In step S174, for each
non-rejected edge, every vertex is transformed from sheer
coordinates to edge coordinates. In this regard, by way of example,
an illustration is provided in FIG. 37 in order to define an
example set of sheet coordinates X.sub.5 and Y.sub.5 on a workpiece
16 having bend lines 1, 2, 3, and 4, which may be transformed to
edge coordinates X.sub.e and Y.sub.e which correspond to the edge
of workpiece 16 which is next to bend line 1.
[0298] In terms of edge coordinates, each edge is discretized ties
into points along the X axis n step S176. Thereafter, in step S178,
for each discretized ties point, X.sub.p, grasp lines are generated
which extend along the Y axis. In order to generate the grasp lines
along the Y axis, several process steps are performed. For example,
referring to FIG. 38, for a discretized point x.sub.p, a (broken)
grasp line 306 is formed along the Y axis. For the discretized ties
point x.sub.p, an initial Y value Ys is proposed which is set at a
distance from the edge (e g., 3 mm). It is assumed that the gripper
is oriented to be normal to the X axis in edge coordinates. A
determination is then made as to whether or not the point Ys is out
of the robot's work space, while the workpiece is at the loader,
the repo station, or at one of the stages. If this is the case, a
new point along a line corresponding to the discretized ties point
Xp and normal to the edge is found that is within the work space.
For the first valid Yp, a determination is made as to whether Yp is
beyond the gripper's maximum reach. If so, the value Yp is rejected
in addition, a determination is made as to whether or not the
gripper can make good pad contact with the part if the gripper is
at the position Yp. If no good pad contact can be made, the
position Yp is rejected. New values for Yp are proposed, until line
306 reaches a first maximum location at which the robot can grasp
the part, that first maximum position being Yf. This distance is
defined by the fact that pads cannot have goad contact any more due
to holes or due to a boundary in the part. For example, a maximum
position Yf is found right before a first hole 307 in the workpiece
16 shown in FIG. 38. The next viable or potential Yp is then found
along the line running perpendicular to the edge and is defined as
a new initial or starting position Ys'. Y values Yp are then
proposed and tested until an additional final position Yf' is found
due to limits because the pads cannot have good contact or due to
the fact that the part has a boundary at that location. Thus, as
shown in the workpiece in FIG. 38, Yf' is determined to be just
before second hole 308. This process is repeated until the end of
the line 306 reaches the gripper's maximum reach or the boundary an
the apposite side on workpiece 16. Thus, an additional line segment
extending from Ys" to Yf" is generated.
[0299] Once the grasp lines have been generated for each
discretized point Xp, later in step S130, a common grasp area is
defined for the present bend in the search, and is defined to be
the intersection of the current grasp lines with the grasp lines
determined for previous bends since the last chosen repo in the
search. A k cost of 0 is assigned if the intersection is not equal
to 0, and a k cost of infinity is assigned if the intersection is
0. This signifies that the present bend cannot be performed since
the grasp areas needed to perform the bend are not common with the
previous bend. Thereafter, in step S182, a temporary grasp location
is selected within a defined common area.
[0300] Whenever it is determined that there is no intersection of
grasp regions, and thus a repo is necessary, final grasp locations
are selected for the bends preceding the repo, since it is known
that the grasp location will not change any further for that set of
bends. A final grasp location is selected such that a large repo
are is generated.
[0301] FIG. 39 illustrates the evolution of the common grasp area
as determined throughout a search, as calculated by a determined
robotic grasp locations process, e.g., as illustrated in FIGS.
36A-36B. The grasp area for bend 1 is first determined as
illustrated in view A. Then, with bend 1 having been already
performed, and the corresponding flange being bent (indicated by
the cross-hatched lines in view 3), the potential grasp regions
which can be utilized to perform bend 2 are determined as
illustrated, in view B. The intersection of the regions in views A
and B is then determined as illustrated in view C. Then, bend 2 is
performed (indicated by cross-hatched lines in view D), and the
total available grasp regions which may be utilized to perform bend
3 are determined as shown in view D. To go from bend 2 to bend 3,
an intersection is made of the regions in views C and D as shown in
view E. This signifies that there is no different intersecting
region and that a repo must be done before bend 3 can be performed
(as indicated by the cross-hatched lines in view F). The repo is
then performed, and bend 3 is performed. Before performing bend 4,
the potential robot grasp regions for that bend are determined as
illustrated in view F. In order to determine the exact grasp
position to perform bend 4, an intersection is made of the regions
in views D and F, as indicated in view G. This is the region for
the robot grasp location that can be utilized in order to perform
both bends 3 and 4.
[0302] Each bend, which has already been performed, is indicated by
cross-hatched lines being placed on the flange that is bent. The
grasp regions are indicated by a solid black line.
[0303] FIG. 40 illustrates first and second views of a workpiece
16, the views showing the grasp line regions determined before
performing a first bend, and before performing a second end,
respectively. As can be seen in FIG. 40, the grasp line region 309
comprises a certain large area of the workpiece 16. The lower view
illustrates the intersection of the grasp line region (i.e., the
grasp area) shown in the top view which can be utilized to perform
the first bend and a grasp line region (not shown) which may be
utilized to perform the second bend. Thus, grasp line region 310 is
a small subset of the grasp line region 309, and may be utilized as
a grasp location to perform both the first bend and the second
bend.
[0304] FIG. 41A illustrates an example embodiment of a process for
determining the repo gripper locations which will be performed
during repo planning after the search as indicated by planning
block P4 in FIG. 29. In a first step S184, an intermediate part is
constructed. The edges which are not appropriate are then rejected
in step S186. For example, the process may reject an edge if it
does net correspond to a face which is parallel to the robot's X-Y
plane. For each non-rejected edge, the steps following step S186
are performed. In step S188, the intermediate part is transformed
from sheet coordinates to edge coordinates. Thereafter, in step
S190, the edge of concern is discretized along the X axis in a
manner similar to that illustrated in FIGS. 33A and 33B) with an
appropriate granularity. Then, in step S192, grasp lines are
generated along the Y axis, by generating points along the Y axis
from a first point Ys (e.g., 3 mm) to the gripper's maximum reach
along the line which is placed on the discrete X point. For every
point along that line, if the repo gripper interferes with a
previous robot gripper location, that Y location is rejected. In
addition, for each Y position, if the repo gripper interferes with
any portion of the part, that Y position is rejected. In addition,
if there is no good pad contact between the repo gripper and the
part, that Y position is rejected. A line is thus drawn as shown ii
FIG. 38 from an initial position Ys to a final position Yf which is
a first maximum position that the repo gripper may grasp the part
until it hits a boundary portion (e.g., a hole in the part).
Additional sets of initial and final positions Ys and Yf are formed
until the repo gripper reaches its maximum reach (e.g., at Yf" as
shown in FIG. 33), in a manner similar to that performed in the
process for determining the robot 's grasp locations as disclosed
in conjunction with FIGS. 36A and 36B.
[0305] A final repo location is assigned (in consideration of
previous and current robot gripper location) when the search
reaches the goal or another repo becomes necessary.
[0306] FIG. 42 illustrates an example embodiment of the process for
performing repo gripper selection before the search. This may not
be actually implemented. In a first step S198, a library of
grippers is read, and in a second step S200, a conservative repo
gripper is selected. A consecutive repo gripper is defined as a
gripper which is narrow and short, and is capable of holding the
part (in either 3D or 2D shapes). The selected repo gripper is a
temporary solution, since a final repo gripper selection will be
performed after the search is completed. The repo gripper selection
after the search is illustrated in FIGS. 43A-43B. In a first step
S202, all the intermediate part geometries for the various bends
throughout the bend sequence are constructed in other words, in
accordance with the order of bends determined from the search, the
appropriate intermediate part geometries corresponding to each bend
within the bend sequence are constructed. Then, in step S204.,
grippers are pruned, which are deemed inappropriate due to obvious
reasons (erg., they cannot grasp a part because of insufficient
dimensions). Then, in step S206 available repo grippers are
identified based upon two robot grasp locations which include an
initial robot (rasp location before the repo and a repositioned
robot grasp location. Each of these positions has been already
determined in the search process. If the previously determined
temporary repo position, determined during the search, could be
improved upon in view of the repo grippers that are identified as
available, then the position is adjusted. In step S208, if there
are more than one available repo grippers (after pruning), then the
repos with the largest width are selected. If there are more than
one repo grippers with the largest width, then the ones with the
smallest length are chosen. If there is more than one repo gripper
with the smallest length, then the one with the shortest knuckle
height is chosen. If there are several repo grippers with the same
smallest knuckle height, then any one of those is chosen.
Currently, a repo gripper is selected such that it allows a larger
robot gripper to be selected and it guarentees a successful
generation of repo gripper locations. The width of a repo gripper
is determined by the dimension of possible area of 3D part for
grasping. The knuckle height of a repo gripper is determined to be
taller than the minimum flange height of 3D part.
[0307] As shown in FIG. 30, in a planning block P12, a bin-packing
algorithm is performed before the search is started. During the
execution of the bin-packing algorithm, a plan is produced that
specifies how the segments should be put together to form each
stage in a list of stages to be chosen from FIG. 44 illustrates an
examples bin-packing algorithm. In a first step S210, the process
builds a list of bend line lengths, and forms a stage length list
having stage lengths equal to the lengths of the bend lines to be
formed an the workpiece. In addition, the process builds or reads a
list of available segment lengths which may be chosen from in order
to form the stages in the stage length list. Then, for each
different bend line length (i.e., for each stage length) each of
steps S212 and S214 is performed. In step S212, an A* search is
performed in order to determine a combination of segments which
could be used to form the particular stage. Then, in step S214, the
process returns a solution set of tool/die segments to the tooling
experts.
[0308] In performing the A* search, the initial node n.sub.0 is
expanded to include a plurality of nodes at the first level of the
search, each of the expanded/successor nodes at the first level
corresponding to one of the available segment lengths (i.e.,
lengths of a tool punch and corresponding die segments). For
example, if the available tool segment lengths are 10 mm, 15 mm, 22
mm, 40 mm, 80 mm and 160 mm, the nodes at the first level would
correspond to each of those segment lengths. The k cost assigned
for each successor node is the length of the segment corresponding
to the present node and the h cost is set equal to the length of a
remaining portion of the stage which is yet to be formed by the
segments (i.e., how far the search process is from the goal)
[0309] FIGS. 45-46 illustrate how the h cost that is assigned by
the tooling expert throughout execution of the search, and
forwarded to the bend sequence planner 72 (in response R12, as
shown in FIG. 30), is calculated. The tooling h cost is determined
as a function of the total number of predicted stages that will be
needed to perform all of the bends in the bend sequence.
[0310] More specifically, h.sub.TE for n.sub.j, h initial is an
initial h cost equal to the total number of predicted stages needed
to perform all bends of the bend sequence multiplied by an
approximate amount of time (e.g., 60 seconds) needed to install
each stage, and k'.sub.TE for n.sub.j is the summed tooling k costs
from node n.sub.0 to node n.sub.j. In order to determine initial h
cost (h.sub.initial) (the total predicted number of stages) a
process is performed before the search (in planning block P13 in
FIG. 30), as shown in FIGS. 45 and 46. A first example workpiece is
illustrated in the top portion of FIG. 45, and a second example
workpiece is illustrated in the bottom portion of FIG. 45. In the
first example workpiece, a total of four bends are to be performed,
and the workpiece is to have a total of five faces after the bends
are performed. In the second example workpiece, a total of four
bends are to be performed, and the workpiece will have a total of
five faces after the bends are performed. In order to assist in the
prediction of the total amount of stages which will be needed to
perform the bends, a bend "test strip" 370 is laid across each bend
line of the 2D representation of the workpiece. In each of the
examples shown in FIG. 45, such a bend "test strip" 370 is laid
across the bend line which is darkened.
[0311] FIG. 46 illustrates an example flow chart of the steps that
may be performed in order to determine the initial tooling h-cost
(h.sub.initial), which is the total number of predicted stages
needed to perform all of the bends on the workpiece. In a first
step S216, a first stage length which is equal to the length of the
longest bend line is placed within the set of assigned stages.
Thereafter, a test is performed for each bend line, by performing
step S218 and the steps following step S218 for each bend. In step
S218, a determination is made as to whether or not an extra stage
is needed. This is done by placing a narrow "test strip" across the
bend line in the manner illustrated by the examples shown in FIG.
45. If a difference value, equal to the total number of faces after
placing the test strip over the bend line minus the total number of
faces before the test strip, is less than or equal to 3, then no
extra stage is needed. Otherwise, an extra stage is needed. In a
next step S220, if an extra stage is needed (i.e., predicted), the
longest stage (from the stage list) that can be used to perform the
bend being tasted is assigned, i.e., placed in the set of assigned
stages. Then, a determination is made in step S222 as to whether
the newly assigned stage is equal to a stage already in the set of
assigned stages. If the newly assigned stage is already in the set
of newly assigned stages, the newly assigned stage is not appended
to the set, as indicated in step S226. However, if it is not
already in the set of assigned stages, the newly assigned stage
will be appended to the assigned stage set in step S224.
Thereafter, the process returns from either of steps S224 and S226
to step S218, if therefore additional bend lines which need to be
evaluated. Once all the bend lines have been evaluated by the
process, the process proceeds to step S228, where the initial
tooling h_cost is set to the product of 600 and the predicted
number of stages (which is the total number of stages which have
been placed in the set of assigned stages).
[0312] Applying the process steps as shown in FIG. 46 to Example 1
of FIG. 45, the faces after placement of the test strip along the
bend line are equal to 8, and the number of faces before the
placement of the test strip along the bend line is equal to 5.
Thus, 8-5=3, and no extra stage is predicted. In Example 2 shown in
FIG. 45, the number of faces after the test strip is placed over
the bend line is 10. 10-5=5, which is greater than 3. Accordingly,
an extra stage is predicted for Example 2.
[0313] FIG. 47A illustrates a tool selection process overview which
forms part at the tool profile selection planning block P11 in FIG.
30. The process begins at the bend sequence planner in step S471,
and proceeds to the tooling expert (tooling module) which operates
in step S472. In response to receipt of a "PLAN" command in FEL
from the bend sequence planner, the tooling expert forwards the
part's geometric model, bend-graph data, and a tool library to a
tool filter module. In step S473, the tool filter module determines
a selected die, die-holder, die-rail and a list of feasible
punches. In determining such information, the total filter module
performs several steps for each bend to be performed an the
workpiece as indicated by the bend-graph data. The tool filter
module reads necessary data for the bend, and selects the die,
die-holder, and die-rail based upon tonnage, V-width, angle and
inside-radius requirements. The tool filter module then prunes the
list of punches (to form a list of feasible punches) based upon
tonnage, tip radius and tip angle constraints.
[0314] The process then returns to the tooling module in step S473,
which then forward the part's geometric model, bend-graph data and
a list of feasible punches to a profile select module. Then, in
step S474, the profile select module selects the punch and punch
holder to be utilized by the bending apparatus. In performing the
profile selection, for each bend, the profile select module selects
only those punches from the feasible list whose profile matches the
geometry of the part. Punches with matching profiles will not
collide with the part during the bending process. The profile
select module then selects the best punch and punch-holder
accordingly. The appropriate selected punch and punch holder are
then returned to the tooling module which continues its functions
at step S475.
[0315] A more detailed explanation of the algorithm performed by
the tool filter module will now be provided. In a first step, the
tool filter module reads the following data: the desired inside
radius (IR) of each bend; the part material thickness (T), the part
material tensile strength; the minimum adjacent flange length (the
minimum/preferred minimum length (height) of the shorter flange
which runs along the bend line of the particular bend of concern);
the bend length and bend angle; and a tool library (the tool
library includes inverted profiles of the punches which can he
used).
[0316] In a second step, for each bend, the tool filter module
performs the following steps:
[0317] (a) A list of FEASIBLE_DIES is set to empty.
[0318] (b) The list of available dies in the library is scanned,
and for each die:
[0319] if its v-width can produce the desired IR within some
tolerance, and if its v-angle closely matches the bend angle, and
if the tonnage-per-meter required for this v-width and T (competed
using a bend force chart and tonnage equations), is within the
tonnage capacity of this die,
[0320] then, add this die to FEASIBLE_DIES.
[0321] It is noted that the tonnage-meter requirement for the
v-width and T may be computed using a force chart and tonnage
equations provided by Amada in their press brake tooling
catalogues. In addition, or in the alternative, the
tonnage-per-meter value may be calculated using the bend chart and
tonnage equations provided in the text entitled "New Know-how on
Sheet-Metal Fabrication Bending Technique," written by the Amada
Sheet Metal Working Research Association, Machinists Publishing
Company, Ltd., First Edition (May 15, 1931), the content of which
has-been incorporated by reference herein in its entirety.
[0322] (c) The die is selected from FEASIBLE_DIES, which most
closely satisfies the IR, bend angle, the minimum flange, and total
tonnage requirements. If the minimum flange length constraint is
still not satisfied, then a warning is issued. The appropriate
die-holder and die-rail for the selected die are then selected for
the selected die.
[0323] (d) The list of available punches in the library is then
scanned, and for each punch:
[0324] if the tip angle is less than but close to the selected
die's v-angle, and if the tip radius is less than and close to the
ER, and if the tonnage-per-meter required for this bend is within
the tonnage capacity of this punch,
[0325] then this punch is added to the, list of FEASIBLE_PUNCHES,
for this bend.
[0326] A more detailed explanation of the seeps performed by the
profile select module will now be provided.
[0327] In an initial step performed by the profile select module,
for each bend, the final (finished) 3D model of the part is aligned
in relation to the appropriate tooling in a position in which it
would be in the bending press after completion of the bend being
evaluated. Then, for each bend:
[0328] (a) The list of FEASIBLE_PUNCHES is scanned for this bend,
and for each punch, if the 3D geometric model of the punch does not
intersect the 3D geometric model of the part at the end of this
bend, then this punch is a FEASIBLE_PUNCH for this bend. The 3D
part model is a sufficient condition, but may be over constraining
and may be modified at a future date. For example, intermediate
part models, representative of the actual shape of the part at each
bend in the sequence could be used as the profile selection is
performed throughout the search process being performed by the bend
sequence planner.
[0329] (b) The punch is selected among the FEASIBLE_PUNCHES, which
most closely satisfies the IR, bend angle, and tonnage
requirements. The standard "robot-tooling" punch will be selected
if feasible. It is noted that the selected punch may have to be
used with its profile inverted (i.e., inverted in the Y
direction/rotated around the Z axis by 180.degree.), in order to
satisfy the intersection test in step (a) above of the profile
selection module.
[0330] It is noted that one or both of the tool filter module and
profile selection module calculations may be performed either
before, during or after the search is performed by the bend
sequence planner.
[0331] FIGS. 47B-47C illustrate a stage planning process which pick
a stage and a location along the stage at which the workpiece will
be loaded when performing a particular bend in the bend sequence,
such planning being indicated in block P14 of the dialogue dialogue
shown in FIG. 30. In a first step S230, an intermediate part model
of the part is formed (with the part having the bends up to the
present bend in the bend sequence).
[0332] In step S232, the biggest non-evaluated stage is chosen from
the stage list (of available stages). Then, in step S234, the
present bend in the search is simulated with tooling expert (TE)
collision checking, with the part being loaded at onto the tooling
stage at a center position with respect to the stage. Then, in step
S236, a determination is made as to whether or not there was a
collision during simulation of the bend. If there was a collision,
the process proceeds to step S238, where the bend being evaluated
in the search is simulated with TE collision checking while the
part is loaded at the left side of the tooling stage, with the left
end of the bend line being placed just to the left of the left side
of the tooling stage. If a collision is then determined in step
S242, the process proceeds to step S246.
[0333] If, however, a collision is not determined to have occurred
in step S236, the position at which the workpiece will be loaded
onto the stage is set to the center position in step S240, and the
process proceeds (via connector B) to step S254 which is shown in
FIG. 47C.
[0334] If a collision is not determined in step S242, after
simulating the bend with the part positioned on the left side of
the stage, the process proceeds from step-S242 to S244, where the
position for loading the workpiece. On the stage is set to the left
position. Then the process proceeds directly to step S254 (via
connector B).
[0335] In stem 5246, the bend is simulated with TE collision
checking with the part positioned at the right side of the tooling
stage (e g., as shown in FIG. 48B), with the part being placed an a
tooling stage so that the right end of the bend line is placed just
to the right of the tooling stage while the bend is performed if a
collision is determined to have occurred during this simulation,
the process proceeds to step S252. If no collision occurred during
this simulation as determined in step S248, the process proceeds
from step S248 to step S250, wherein the loading position is set to
the right position, before the process proceeds to step S254. If a
collision did occur as determined at step S248, the process
proceeds to step S252, wherein the chosen stage (chosen in step
S242) is disregarded, and the process proceeds (via connector C) to
step S232 at the top of FIG. 47B. It is noted that the next
non-evaluated biggest stage from the stage list will be chosen in
step S232 at this point. However, the stage planning process may be
designed so that it will go from a "failed" biggest stage straight
to a stage having a length approximately equal to the bend line of
the particular bend being evaluated.
[0336] In step S254, the evaluated stage is deemed a solution
stage. Thereafter, in step S258, the stages are arranged along the
die rail, and in step S256, the necessary left-right clearances for
stage juxtapositioning are computed.
[0337] The above-referenced tooling expert (TE) collision checking
process, referred to in each of steps S234, S238 and S246, may be
performed as follows:
[0338] The tooling expert collision checking comprises mainly an
intersection determination. The intermediate part corresponding to
the particular bend being evaluated in the search is formed, and is
further converted to a B-rep (boundary representation) which is
compatible with the NOODLES geometric modeler. Then, an
intersection is performed utilizing the appropriate NOODLES
function. First, the number of faces of the part, as it changes
shape throughout performance of the bend, are monitored. For each
of a plurality of discretized shapes of the part throughout
performance of the bend, each of these shapes are intersected with
the appropriate tools of the bending workstation during the
performance of the bend. The resulting number of faces of the part,
for each shape, is then counted. If the resulting number of faces,
intersected with the tools, is greater than the expected number for
that shape, then there has been a collision.
[0339] The above-described steps define a preferred algorithm for
performing a tooling expert collision checking process. In the
alternative, the intermediate part before and after the bend may be
modeled by a bounding box, and the basic solid intersection
function provided by NOODLES may be utilized to determine if the
tools intersect with the bonding box representation of the
workpiece for the particular bend being evaluated during the
search.
[0340] A description will now be given of a process for determining
the necessary left-right clearances for juxtapositioning the stages
along the die rail, as computed in step S256 of the process
illustrated in FIGS. 47A-47B. The lateral limits of the part at the
particular bend being evaluated are calculated based upon the
amount by which the workpiece extends beyond a side edge of the
solution tooling stage, and a largest lateral limit for each side
of the stage is determined. The stages arranged adjacent to the
present solution stage are then appropriately spaced to have a gap
between the adjacent side edges which is greater than or equal to
the larger of the determined largest lateral limits of ate adjacent
side edges.
[0341] In arranging the stages, in step S258 of the stage planning
process shown in FIGS. 47B-47C, the present solution stage
(corresponding to the presently evaluated bend) is placed in the
middle of the die rail if it is the longest solution stage that has
been evaluated so far in the search. On the other hand, if it is
the shortest stage that has been decided upon at the present point
in the search, then it is placed at the first or left position
along the die rail. All middle gradations, roam the second largest
down, are respectively positioned from the third position to the
last position along the die rail, the third position being
positioned just to the right of the middle position, and the last
position being the position furthest to the right.
[0342] Additional considerations must be taken into account by the
bend sequence planner to arrange the layout of the stages when
co-linear bends are to be performed simultaneously in performance
of the operation sequence. There are issues which must be taken
into account, such as the clearance of the part with respect to the
stages when the co-linear bend is being performed, and the sizes,
arrangement, and number of stages that are needed in order to
accommodate the co-linear bend while at the same time best using
the resources at hand. One particularly important resource that
must be conserved is the use of space along the die rail in order
to set up the stages. The number, sizes, and spacings of the stages
may be limited because of limitations in die rail space.
[0343] When planning the staging for performance of a particular
co-linear bend, a decision should be made as to whether the
co-linear bend can be done with only one stage, or whether two
spaced stages are needed in order to allow clearance therebetween.
Accordingly, the tool expert should consider whether the co-linear
bends are interrupted (as is the case in FIG. 20E) or
non-interrupted (meaning that one stage can be used for bath bends,
as is the case in FIG. 20D)
[0344] A search algorithm could be used, such as A*, in order to
come up with an appropriate stage layout that can accommodate
co-linear bends, while minimizing the number of stages and the
spacing between stages that are needed. A significant cost to be
taken into account by such a such algorithm is the total length of
the die rail, the amount of space along the die rail a certain
staging solution will occupy, and amount of space along the die
rail remaining at the present level of the bend sequence (being
generated by the bend sequence planner).
[0345] FIGS. 48A-48C illustrate respective intermediate
representations of a workpiece, being modeled in relation to the
tooling during performance of a bend. In FIG. 4B, the workpiece is
at a right position along the stage. In each of FIGS. 48A and 48B,
the bend line is shorter than the length of the tooling stage. In
FIG. 48C, the workpiece centered along the tooling stage, where the
bend line is slightly longer than the length of the tooling
stage.
[0346] In each of the graphic representations shown in FIGS.
48A-48C, the various components of the bend press are modeled,
including the tool punch and the die, along with an intermediate
representation of the workpiece.
[0347] FIG. 49 illustrates a fine motion planning process, which
may be performed in planning block P14 of the dialogue chart shown
in FIG. 30. In a first stem S260 of the process illustrated in FIG.
49, parameters are set and initialization steps are performed. In
this regard, the 3D models of the tooling and the part are read,
and various initialization functions are performed. The goal
parameters are set up based upon the tool and part geometry, and
the desired clearance. In addition, the portion of the part inside
the bend line is rapidly analyzed, and a bounding box that
surrounds the part is computed.
[0348] In step S262, a determination is made as to whether or not a
simple solution path is readily available, by testing if the to a
of the part can clear the bottom edge of the tooling punch, and if
certain features of the part satisfy constraints imposed by the
tool geometry and the die opening. If such a simple solution path
is readily available, the process proceeds to step S264, where a
fine motion plan is quickly generated. The process is then
forwarded to step S270 where it returns to the tooling expert with
the sine motion plan and the fine motion cost, which is equal to
the amount of time that it takes to unload the part from the bend
press.
[0349] If a simple solution is not available as determined at step
S262, the process proceeds to step S266, in which a modified A*
search is performed. In performing the search, a plurality of
feasible virtual configuration space nodes are generated and placed
on the OPEN list with their respective costs. The first level of
the search includes several generated intelligent direction
feasible VC (virtual configuration) space nodes that were appended
to the OPEN list. When a node from the OPEN list is expanded, it is
expanded to include several neighborhood nodes representative of
locations in the general neighborhood of the parent node. Each
expanded node is tested for feasibility by utilizing a geometric
intersection test. If the test is positive (i.e., there is no
collision by the use of a negative intersection function), the
expanded node is appended to the OPEN list along with its cost. The
cost is an h cost which is set equal to the Euclidean distance from
the expanded node to the goal. The nodes on the OPEN list are
continually expanded to lower levels in the search tree until the
goal is reached or until the OPEN list becomes empty.
[0350] At step S263, a determination is made as to whether or not
the goal was reached. If the goal was reached, the tine motion
planning process returns to the tooling expert with the fine motion
costs and the fine motion plan in step S270. If the goal was not
reached, the process proceeds to stem S272, where the fine motion
cost is set to infinity, and is sent to the tooling expert.
[0351] FIG. 50 illustrates an example process for determining the
motion expert k and h costs, as indicated in planning box P21 of
the dialogue chart shown in FIG. 31. In a first stem S274, the k
cost is calculated to be equal to a calculated robot travel time to
take the part from a position at a stage of an immediate preceding
bend to the stage location corresponding to the presently evaluated
bend in the search, without regard to collisions. Then, in step
S276, the h cost is calculated to be equal to the product of the
running average of the k cost values for the previous bends and the
presently evaluated bend, and the sum of the number of remaining
bends and twice the number of remaining predicted repos that will
have to be performed before all of the bends in the bend sequence
are completed.
[0352] In forcing the gross motion scheme and the gross motion
paths after the search is performed, as indicated in planning block
P22 of the dialogue chart shown in FIG. 31, a state-space search
algorithm, particularly an A* algorithm, may he performed to form
each of the steps along the path from one point to another in order
to bring the workpiece throughout its various stages in the bend
sequence. When generating a path from an initial start position to
a goal position, for a particular operation of the bend sequence,
before deciding that the path will be the final path to be used,
collision checking may be performed. In order to perform this
collision checking, the workpiece, the robot, and the bend press
may each be modeled, and intersection tests may be performed using
the appropriate NOODLES functions. FIG. 51 illustrates a geometric
model of a press brake 304, a workpiece bounding box 300, and a
robot 302. In performing collision checking in connection with the
gross motion planning, the workpiece is modeled by a bounding box
300. In FIG. 51, the position of the robot 302 and the modeled part
300 is shown in three positions extending between a stage used for
the final bend of the bend sequence to a position at the far right
of the diagram which corresponds to a position ready for unloading
by the loader/unloader.
[0353] 4. Geometric Modeling
[0354] Each module of planning system 71 utilizes geometric
modeling functions in order to analyze the physical relationships
between various components of the bending workstation and the
workpiece as it is being moved and developed. Such geometric
modeling functions may include representing stock, intermediate,
and final parts, checking for interferences during motion planning
and assisting in selecting robot grip positions. In addition,
needed geometry information may be provided to assist the
sub-planners in determining punch geometry selection, tool
placement, loader/unloader suction cup 31 placement, and
interpretation of sensing signals. Simplified geometric
representations may be provided for fast computations (e g.,
bounding boxes, convex hulls, and 2D cross-sections), which may be
needed to perform geometric-based reasoning methods (e.g., oct-tree
representations, and configuration spaces). A geometric database of
physical components may be provided which includes both symbolic
descriptions (e.g., labeled features) along with actual geometry
data of physical components. Other geometric modeling functions may
be provided, although they are not specifically enumerated
herein.
[0355] In a particular embodiment of the present invention, NOODLES
is utilized to perform many of the noted modeling functions.
Several reasons may be given for using NOODLES to implement the
geometric modeling functions. NOODLES includes a large package of
geometric routines and is accessible to C/C+C++ source code. In
addition, NOODLES is capable of handling non-manifold geometry
(e.g., 0D, 1D, 2D, 3D, etc.) with the same routines, and has a
hierarchal structure which can be used to build geometry libraries
and to store various types of information regarding features of
parts.
[0356] A modeling mechanism (not shown) nay be provided for
modeling both upper and lower surfaces (i.e., the thickness) of
each sheet metal workpiece throughout one or more of the design,
planning, and execution phases of the bending process. It may be
useful to have such a complete thickness representation in the
workpiece for certain aspects of the system. For example, holding
expert 82 may benefit from the added knowledge of knowing both the
upper and lower surfaces of the workpiece, and motion expert 84 may
be able to better plan for and control fine motion of the work
piece when it is close to the die and punch tool before and after a
bending operation.
[0357] Referring to FIG. 10, an upper/lower surface modeling
mechanism (not shown) performs a thickness transformation between a
flat representation 114 and a representation with thickness 116,
shown at the right of FIG. 10. Essentially, the representation with
thickness 116 comprises two flat representations juxtaposed one on
the other.
[0358] FIG. 11 illustrates an overlapped flange 118 modeled as a
flat representation 114 at the left of FIG. 11, and transformed to
a representation with thickness (i.e., a solid model). Solid model
116 is shown to be equal to an upper surface representation 120
together with a lower surface representation 122. Upper surface
representation 120 is shown in solid lines, and lower surface
representation 122 is shown in dotted lines.
[0359] FIG. 12 represents an exemplary tree structure which may be
utilized to model the design representation of a sheet metal
workpiece 16. At a first level, a plurality of shapes 126 are
indicated corresponding to workpiece 16. For each shape 126,
several faces 128 are defined, and for each face, several edges 130
are defined. For each edge, a plurality of vertices 132 are
indicated. For each vertex, a 2D (i.e., stock part) representation
134 may be maintained, along with a 3D (i.e., final part)
representation 136 and an intermediate representation 13.
[0360] A thickness transformation may be performed, as represented
by arrow 140, resulting in upper and lower surface representations
142, 144, which each have a tree structure similar to that
illustrated above the line in FIG. 12.
[0361] FIGS. 17A-17B and 18A-18B illustrate several different types
of geometric libraries which may be provided in order to aid in the
performance of geometric modeling of the system.
[0362] For further information regarding the NOODLES modeling
system, and geometric modeling in general, reference is made to the
Reference Manual for the Noodles Library, by E. Levant Gursoz,
EDRC, Carnegie Mellon University, Pittsburgh, Pa., and a back by
Michael E. Mortezison, entitled Geometric Modeling. The contents of
each of these documents are expressly incorporated herein by
reference herein in their entireties.
[0363] 5. The Query-Based Module Communicating Language (FEL)
[0364] In order to formalize the interface between each of the
modules of the planning system, a query-based language called FEL
may be used. FEL was originally developed by David Bourne in 1988,
and has since been further refined. For more detailed information
regarding FEL generally, reference should be made to the several
user guides provided by the Robotics Institute at Carnegie Mellon
University including: "Feature Exchange Language Programmer's
Guide." David Alan Bourne, Duane T. Willis (Jan. 14, 1994); "Using
the Feature Exchange Language in the next Generation Controller,"
David Alan Bourne, Duane T. Williams, CMU-RI-TR-90-19; and "The
Operational Feature Exchange Language," David Alan Bourne, Jeff
Baird, Paul Erion, and Duane T. Williams, CMU-RI-TR-90-06. The
contents of each of these FEL documents are hereby expressly
incorporated by reference herein in their entireties.
[0365] FIG. 19 illustrates an exemplary F-L planning message 145
which is being sent from bend sequence planner 72, as is indicated
by expression 146, to motion expert 84, as indicated by expression
148 FEL planning message 145 comprises a query command sent from
bend sequence planner 72 to motion expert 84, which provides
preliminary information to motion expert 84 so that it may satisfy
the query. An initial parameter setting-portion 150 of message 143
is provided immediately after a main verb/command "get" 152, and
includes expressions "type message" 147, "from planning" 146, "to
moving" 148, and "state request" 149. The expression "type cost" is
provided immediately after setting portion 150, and signifies that
a request is being made for the motion expert to tell the planner
how much a particular operation will cost. The next expression
"bends . . . " 156 queries how expensive it will be to perform bend
number 3, after having done bend number 6. The numbers 7 and 1
represent a face of the workpiece that will be inserted into the
die space of the bending workstation for bends 6 and 3,
respectively.
[0366] A next expression "average_cost 2-321" 158 informs the
motion expert that this is the average cost (k-cost) for motion per
bend for the bends that have previously been done based upon cost
values previously assigned by the motion expert. In this case, the
average cost is 2.321 seconds per bend previously performed. A next
expression "flange-before_bend" 160 indicates the height (in
millimeters) of the tallest flange of concern (indicated in FIG.
18A as 11 millimeters) to be used by the motion expert to make
clearance determinations. Expression "flange_after_bend" 162
similarly indicates the height (in millimeters) of the tallest
flange of concern which will exist after the bend is performed
(indicated in FIG. 18 as 17.5 millimeters) A next expression
"robot_loc" 164 informs the motion expert there the part is by
specifying the location of the robot (as it was left upon
completion of the previous bend). A last expression in the planning
message 145, "bendmap" 166, indicates the respective tool stages
for the previous bend and presently proposed bend and where the
workpiece should be with respect to the stage for each bend. The
first value 168 represents that the location information is given
for bend number 6, and a second value 170 indicates the stage at
which bend number 6 was performed, which in this case is stage
number 1. Several coordinates are listed to the right of the first
and second values 163, 170. The first coordinate value "257."
represents the position of the left edge of the part with respect
to the left edge of the stage, and the second coordinate value
"-257" represents the position of the left edge of the part with
respect to the stage. The value "350.7" represents the position of
the right edge of the part with respect to the stage. The final
value "320." represents the position of the stage along the die
rail with respect to the left edge of the die rail.
[0367] Generally speaking, the planning message 145 forwards all
the information which the motion expert will need in order for it
to generate a subplan for moving the workpiece from an initial
position (where it is left after performance of a preceding bend)
to a position ready for a proposed next bend.
[0368] A significant feature of the query-based interface structure
between the planner and its various sub-planners (experts) is that
when the planner forwards a query to am expert, it informs the
expert of all background information that the expert will need to
respond to the query. Thus, the experts need not save information,
but can simply respond to the bend sequence planner and return al
related information for the bend sequence planner to save.
[0369] (a) Configuration of FEL-Based Process Planner
[0370] In configuring the process planner 71 illustrated in FIG. 5,
each module including bend sequence planner 72, and experts 80, 82,
and 84, is sent a command to read its startup configuration file.
An example of such a command could be as follows:
[0371] (read((type file (name "config.s 2.fel")))
[0372] ((type message)(from planning)(to tooling)(name
"config")))
[0373] After each module has read is startup configuration file,
the system will be set so that bend sequence planner 72 can use any
specified number of experts, e.g., using a command such as the
following:
[0374] (set((type experts)(experts(tooling grasping moving))))
[0375] After the experts to be used by bend sequence planner 72 are
specified, the part design may then be read from C-D system 74 into
each module as needed, and bend sequence planner 72 may start the
planning process.
[0376] (b) FEL Commands
[0377] The following table lists several commands that may be
specified by bend sequence planner 72 in participating in a
dialogue with the other modules of the system, including the
experts.
1 FEL MODULE DIALOG COMMANDS SEARCH COMMANDS Finalize collect final
plan info from each module Get get cost information (and other
data) for a bend Plan initialize a module for planning a part USER
COMMANDS Quit cleanup and exit a module Read read files for
planning Set set various module options Show show various module
data to user
[0378] The following table lists several commands that may be
specified by bend sequence planner 72 for execution by sequencer
77.
2 FEL SEQUENCER COMMANDS Print print messages for BM100 operator
for Messages setup Programs download programs to NC9R press
controller and backgage controller Startup initialize state of
press and robot Get acquire part from various steps of the process
Put load part into various steps of the process Move move the robot
through a series of points Bend initiate bend sequence (backgage
and bending)
[0379] The `read` command may be used to instruct a module to read
certain files needed for planning, the files being representative
of the design to be produced, and to configure itself in accordance
with the design. With use of the "set" command, various module
functions may be set, e.g., how to display information, how to
interface with other modules, and so on. The `show` user command
may be utilized to show various module data to the user, erg., the
various nodes of the A* algorithm which represents the various
costs or different bends within the proposed bend sequence.
[0380] 6. Part Design and Modeling
[0381] In the illustrated embodiments shown in FIG. 5A, a C-D
system 74 performs several functions relating to part design and
part modeling for planning system 71 CAD system 74 allows a user to
form a design of a given workpiece by working with simplified,
primitive components (in either 2D or 3D form) on a graphic
interface, each primitive component having certain desired
dimensions which may be input by the user, in order to design the
workpiece. The user may then utilize a user interface with CAD
system 74 to connect the primitive components and, in addition, to
remove portions, such as holes, slots, etc., from the connected
primitive components. CAD system 74 may then perform feature
labeling functions including labeling several geometric features of
the workpiece, such features having a particular significance in
the context of sheet metal bending. CAD system 74 may also build a
bend graph which associates various bend-related information with
the geometric design of the workpiece CAD system 74 thereby forms
an output file which includes geometric, topological, and
bend-related feature information (including a list of labeled
features and a bend graph). All of this information is then placed
into an output shape file which will form the basis of
communication with other modules of planning system 71. In this
regard, a part modeler may be provided to form an interface between
the design system's output shape file and the various expert
modules 80, 82, and 84 (and 85) along with bend sequence planner
72.
[0382] A part modeler may be provided which performs various
conversions on the data provided in the output shape file in order
to form developed part data structures which can be used for
geometric modeling purposes by each of the modules of planning
system 71. Part modeler may be implemented in the form of a library
which is accessible to each of the modules in planning system 71,
which may be utilized to manipulate the information in the
developed part data structures and/or undeveloped data structures
provided in the output shape file, in order for the various modules
to utilize the information provided therein to serve any particular
purpose that they may be addressing at a particular point in
time.
[0383] FIG. 13A illustrates a functional black diagram of a design
system 311 which may be provided to perform the functions of CAD
system 74 of the illustrated embodiment. Design system 311 performs
several design-related functions which may be implemented in the
form of function modules as illustrated in FIG. 13A. Each function
module may be implemented by a particular function prided in a
library of functions comprised by the design system. The functions
shown in FIG. 13A include a user interface 312, file I/0 314, view
316, simulation 318, shape defining 320, hole defining 322, editing
324, and feature labeling 323. Each of these functions may be
controlled by a design system control module 326. In order to
perform several feature labeling functions, bend graph module 330
and bend deduction module 332 are each connected to feature
labeling module 328.
[0384] Each of the functions are illustrated in FIG. 13A in the
form of function modules. However, it is not necessary that each of
these functions be separated into separate modules in the specific
manner as illustrated. In the alternative, an overall program or
hardware system may be provided which allows each of these
functions to be performed without having any specific interface
with other functions of the design system. For example, one
complete routine may be provided within a processor of a computer
to implement each and every one of the functions of the overall
design system, without removing several of the general benefits
provided by the design system disclosed herein.
[0385] The file I/O module 314 performs functions such as reading,
writing, printing, and performing data exchanges between modules.
The view function module 316 performs functions such as zooming
in/cut, and panning during display of the part an a graphic
interface. The shape module 320 is provided to allow a user to
specify particular shares, including rectangular shapes, angles, a
Zee, a box, a hat, and so on, which may be put together to form a
particular workpiece design. Hole module 322 is provided for the
user to specify various type of cavities to be provided in the
workpiece, such as cutouts, holes, slots, notches and so an, to
further allow the user to design the workpiece in a manner similar
to that provided by shape module 320. Edit module 324 is provided
to allow the user to perform various editing functions such as a
fillit function, a chamfer function, and changing the workpiece
material type and/or thickness. Simulation module 318 is provided
so that the user can is simulate bending and unfolding of various
bends on the workpiece, thus to get a visual representation of such
bends on the graphic interface to be utilized by the design
system.
[0386] Feature labeling module 328 is provided to automatically
assign feature labels which pertain to sheet metal bending, and
which will thus be useful to the planning system 71 illustrated
herein in forming or generating a bend sequence plan with the use
of such feature labels. Feature labeling module 328 may generate
feature-related information such as corners, setbacks, form
features (e.g., dimples, louvers), holes, large radius bend, etc.
In addition, feature labeling module 328 may be designed so that it
directs a bend graph module 330 to farm a bend graph which includes
information organized in a certain way to relate the geographic and
topological information to the various bends to be performed on the
2D workpiece to form the desired 3D finished workpiece. In
addition, feature labeling module 328 may be designed so that it
directs the performance of bend deduction calculations by a bend
deduction module 332. The resulting bend deduction information may
then be placed within a Bend graph listing provided by bend graph
module 330.
[0387] Various modules provided in the planning system 71
illustrated herein perform various geometric modeling functions
which require that a part (i.e., a workpiece) be modeled.
Accordingly, a part modeler should be provided, and may be provided
in the form of a library of functions accessible to the various
modules in order to interface between the design system's output
shape files and the various modules within planning system 71. FIG.
13B illustrates a part modeling system 333 for performing this
function. Part modeler 333 includes two main function modules: a
B-REP rearrangement module 336 and an intermediate shape conversion
module 342. The B-REP rearrangement module 336 converts an is
undeveloped part data structure 334 to either or both of a
developed 3D part data structure (in B-REP) 338 and a developed 2D
part data structure (in B-R) 340. Intermediate shape conversion
module 342 converts the developed 2D part data structure (in B-REP
340) to a developed intermediate part data structure (in B-REP)
344.
[0388] The undeveloped part data structure 334 (provided by the
design system 311 as illustrated in FIG. 13A) defines a
geometric/topological data structure that does not take into
account bend deduction and that forms part of the output shape file
produced by CAD system 74. A developed part data structure, such as
developed 3D part data structure 338 and developed 2D part data
structure 340, includes a modified representation of the part that
takes into account bend deduction. The noted developed part data
structures are further converted to be in the form of a boundary
representation (B-rep) model.
[0389] The data structure which resides in the shape output file
produced by the CAD system may be designed to include a shape
header which includes part information, followed by a plurality of
shapes in a linked list, the linked list ending with a null. In
each shape, topological and geometric information may be provided
for both a 3D and a 2D representation of the part. The structure of
the shape may include a list of information including the shape
type, shape identification, a face list, an edge list, a 3D
vertices list, and a 2D vertices list. Each face may have its own
structure, which may include a list of information including a face
identification, the number of vertices of the face, a vertices list
for the vertices of the face, and a face normal vector. For each
edge, a structure may be provided which includes information such
as the edge identification, the edge type, the bent line type, and
the vertices index number for that particular edge. For each
vertex, information may be provided including the vertices
identification, vertices coordinate, 2D coordinates, 3D coordinates
and intermediate coordinates. Further information regarding the
details of data structures and the illustrated CAD system in
general are provided in an ME report dated May, 1992 entitled "A
Parallel Design System for Sheet Metal Parts" presented by
Cheng-Hua Wang at the Mechanical Engineering Department, Carnegie
Mellon University, Pittsburgh, Pa., the contents of which are
expressly incorporated by reference herein in its entirety
[0390] As noted above, the CAD system preferably employs a
concurrent "parallel" representation of both the 3D and the 2D
versions of the part as it is being designed, and such
representations are maintained once the part is finally designed
for use by planning system 71. In order to demonstrate one of the
benefits associated with having such a concurrent and parallel
maintenance of 3D and 2D data representations, FIGS. 13C and 13D
are provided. One of the benefits of having a concurrent and
parallel design system is that such a system resolves ambiguities
which may other-wise occur in the design process. For Rumple, a 2D
part 346a is illustrated in FIG. 12C and a 3D part 346b is shown in
FIG. 12D. By viewing just the 3D representation of 346b of the
part, one may not notice that inner tab 347 is too long, and cannot
possibly be formed from a single, malleable piece of sheet metal.
This is only clearly evident by viewing the 2D representation 346a
of the part, which illustrates the overlap of inner tab 347 as it
crosses an inner edge portion 348 of the part. Accordingly, as can
be seen in FIGS. 13C and 13D, by having both the 2D and the
concurrent 3 representations in a graphic form, the designer can
easily resolve ambiguities and recognize errors in the design which
might otherwise be detected due to ambiguities in just viewing one
or the other of the 2D and 3D representations during a design.
Another benefit associated with such a concurrent design approach,
as noted above, is that it may be easier to make modifications to
one representation (e.g., the 2D representation) instead of the
other for a particular type of modification, e.g., adding an inner
tab to the part.
[0391] FIGS. 14A-14E illustrate a design system graphical user
interface 348, with its display changing throughout the process of
designing a certain desired part. Ref erring, e.g., to FIG. 14A,
graphical user interface 348 includes a key pad 350, a parameters
window 352, a primitive shape 3D window 354, a primitive shape 2D
window 356, a model 3D window 358 and a model 2D window 360. FIG.
14A shows the first introduced primitive shape provided on a
graphical interface 348 in order to produce the desired workpiece
as shown in FIG. 14E. The first primitive shape is a box. The
parameters of the box may be specified with the use of key pad 350
and are illustrated in parameters window 352 to have a base which
is 100.times.100 (indicated by parameters PC[1] and P[2]), and a
height equal to 20 (indicated by parameter [3]). The 3D version of
the primitive shape is illustrated in primitive shape 3D window
354, and the 2D shape of the primitive shape is illustrated in
primitive shape 2D window 356. Since this is the first primitive
shape being provided for the part design, model 3D window 358 is
identical to primitive shape 3D window 354, and model 2D window 360
is identical to primitive shape 2D window 356.
[0392] FIG. 14B illustrates the next shape to be added which is a
rectangle having a length of 100 (indicated by parameter [1]), and
a width of 15 (indicated by parameter [2]). The next primitive
shape being added to design the part is another rectangle having
the same parameters as the rectangle of FIG. 14B. The next
primitive shapes are added to the workpiece as shown in FIGS. 14C,
14D and 14E.
[0393] It is noted that for each primitive shape which is added to
the workpiece, a dotted line is utilized to indicate a bend line.
Parameter P[1] corresponds to the X dimension, P[2] corresponds to
the Y dimension, and parameter P[3] corresponds to the Z dimension
of the primitive shape being added.
[0394] FIGS. 15A-15C are provided to illustrate bend deduction, and
the manner in which it relates to the 3D and 2D dimensions of
flanges of a workpiece. Where a workpiece 362 has a thickness t,
and the flanges of the workpiece 362 are desired to have lengths a
and b, a calculation should be performed so that the flat 2D
representation of the part, when bent along the appropriate bend
line, will indeed form the flanges having appropriate dimensions a
and b, taking into account the thickness t of the material, the
material type, and the internal radius of the bend line (to the
inside surface of the sheet metal). Starting with an undeveloped
representation 363 of workpiece 362, the developed 2D
representation 364 of workpiece 362 may be calculated by
subtracting the appropriate bend deduction (BD) value from the
overall dimension a+b. Methods for performing such a calculation
are known manner. Accordingly, no specific details are given herein
regarding the equation used for determining the bend deduction (BD)
value.
[0395] FIG. 16 illustrates a graphic representation of a bend
graph, the graphic representation being a 2D representation of the
workpiece designed in the steps illustrated in FIGS. 14A-14E. The
bend lines of the designed workpiece are labeled as bend lines B1,
B2, . . . B8, and each label comprises a bend line index. Each bend
line index is then assigned a bend sequence number which comprises
an initialization value. The bend sequence number indicates the
order in the bend sequence in which the bend line will be bent, and
is assigned for each bend line in accordance with the plan (i.e.,
the bend sequence) produced by the bend sequence planner of the
illustrated planning system 71. In addition, to the bend line
indices, each bend line is assigned a bend angle. For example, in
the bend graph illustrated in FIG. 16, an angle or -90.0.degree.,
is given for bend B2, and a bend angle of 90.0.degree. is given for
B1. The bend graph further comprises an indication of the various
faces F1-F9 which are formed on the workpiece once the bends are
performed
[0396] Listings are provided in Appendices A and B which
respectively include a geometric/topological data structure and a
bend graph listing for the part designed in FIGS. 13A-13E. In
addition to the above-noted report to the Mechanical Engineering
Department of Carnegie Mellon University, further reference may he
made to an article by Cheng-Hua Wang and Robert H. Sturges,
entitled "Concurrent Product/Process Design with Multiple
Representations of Parts," IEEE (1993) 1050-4729/93, the content of
which is expressly incorporated by reference herein in its
entirety.
[0397] 7. Sequencing and Control
[0398] FIG. 52 comprises a block diagram of the various software
modules and their main interfacing components, such modules
including planner 72, sequencer task 76, robot task 92, press and
L/UL task 94 and backgage tasks 96, speed control task 100, and
collision detection task 100. Planner 72 includes interfacing
components such as an output queue 72a and input queue 72b. The
sequencer task 76 includes an input queue 76a, an output queue 76b,
a task response queue 76c and a section corresponding to several
task class member functions 76d. Output queue 72a of planner 76 is
connected to input queue 76a of sequencer task 76. Output queue 76b
of sequencer 76 is connected to input queue 72b of planner 72.
[0399] Robot task 92 includes an input queue 92a, an output queue
92b, and a portion corresponding to robot task functions 92c. Press
and L/UL task 94 includes an input queue 94a, an output queue 94b,
and a portion corresponding to press task functions and L/UL task
functions 94c. Backgage task 96 includes an input queue 96a, an
output queue 96b, and a portion corresponding to backgage task
functions 96c. Each of input queues 92a, 94a, and 96a is connected
to input queue 76a of sequencer task 76. Each of output queues 92b,
94b, and 96b is connected to task response queue 76c of sequencer
task 76.
[0400] The controller software structure shown in FIG. 52 is
representative only of an example of the inner connections between
planner 72, sequencer task 76, and control system 75, the structure
of each of the tasks, and how they are connected. It is within the
scope of the invention disclosed herein to provide variations of a
control system which performs the same essential controlling
functions, without being implemented in the manner illustrated in
FIG. 52.
[0401] FIG. 53 illustrates an example flow of the process performed
by sequencer task 75 illustrated in FIG. 52. Once the sequencer is
started, in a first step S280, the sequencer will obtain a new
message from the FEL listing at input queue 76a. In step S282, the
sequencer will parse the FEL sentence, and in step S284, the
sequencer will create a data object for each task involved. In step
S286, the appropriate data objects will be placed upon their
appropriate task queues (e.g., an one or more of the input queues
of robot task 92, press and L/UL task 94, and backgage task 96). In
stem S288, the sequencer checks the state of all tasks involved.
Thereafter, in step S290, a determination is made as to whether all
the tasks are finished. If not, the sequencer proceeds to step
S292. If all the tasks have finished, the sequencer proceeds from
step S290 to step S294 where appropriate cleanup operations are
performed (e g., destroying data objects and resetting flags).
[0402] If all the tasks have not finished as determined at step
S290, in the next step S292, a determination is made as to whether
or not a time out has been exceeded. If not, the process returns to
step S288. If the time out has been exceeded, the sequencer
proceeds to step S293 where appropriate error recovery processing
is performed. After the cleanup operations are performed in step
S294, a determination is then made in step S296 as to whether the
task exit signal has been set. If the task exit signal has been
set, the process will then terminate. Otherwise, the process will
return to step S280 where a new message will be acquired from the
FEL input queue.
[0403] FIG. 54 is a flow chart of the overall bending process
during execution of a single bend. In execution of the bending
process, in a first step S298, the robot places the part into the
die space. Thereafter, the part is aligned in the X, Y and rotation
directions. This alignment is part of the backgaging operation. In
step S300, the press table is raised to the pinch point, i.e., the
point at which the die contacts the workpiece, which in turn
engages with the punch tool so that the workpiece is in a
semi-stable state pinched between the die and tool punch. In step
S302, the bend is executed with bend following (i.e., with the
robot gripper maintaining its hold on the workpiece throughout the
execution of the bend). Thereafter, in step S304, the press brake
will be opened. Then, in step S306, the part is unloaded from the
die space. Once the part is unloaded, the bend is completed.
[0404] FIG. 55 illustrates the robot task 92 and the various
functions that may be provided therein, including general motion
functions and sensor-based motion functions. The general motion
functions may include a joint space move a cartesian move, and
rotation about a point. The sensor-based motion functions may
include a guarded move, bend following, open loop bend, active
damping, contact control, and compliant-part loading.
Compliant-part loading comprises loading a vibrating compliant-part
into the die space of the proper timing so that the part fits in
the die space and does not collide with the workstation.
[0405] FIG. 56 illustrates the press and L/UL (loader/unloader)
task 94, and the various functions that may be provided within the
task. The functions that may be provided for controlling the press
may include raise press, lower press, and bend. The L/UL functions
may include a load workpiece, release workpiece, grasp product, and
unload product.
[0406] FIG. 57 illustrates the backgage task 9-6, and the various
functions that may be provided therein. The backgage task may
include general motion functions and sensor-based motion functions.
One general motion function may include a move function. The
sensor-based motion functions may include a find part edge and a
guarded move function.
[0407] 8. Learning for Speed and Quality
[0408] The bend system illustrated herein may be provided with one
or more mechanisms for learning from the results of the one or more
initial runs of a plan, and for modifying the plan accordingly in
order to improve the speed of operations and to also improve the
quality of the resulting workpiece. In this regard, a sensor-based
control mechanism may be provided for performing an operation,
including moving a workpiece from one position to another. The
bending apparatus may use a sensor output to modify the movement of
the workpiece, but measure the amount by which the movement of the
workpiece is modified due to the sensor output. Then, by learning
the amount by which the movement of the workpiece was modified, the
operation may-then be controlled, based upon what was learned, so
that the workpiece is moved from one position to another without
modifying the movement of the workpiece utilizing a sensor
output.
[0409] FIG. 58 illustrates an example process for performing
learning measurements and for modifying movement control during
multiple executions of a generated bend sequence plan, where the
movement of the workpiece from one position to another comprises
droop compensation and backgaging in the X direction. The sensor
output comprises a measured amount of X offset and a measured
amount of droop offset of the part.
[0410] In a first step of the illustrated process, S308, the part
is loaded for bending using droop sensing. The amount of offset of
the part, i.e., the amount by which the part is drooping, is sensed
and sent back to the planner (e.g., planner 72 illustrated in FIGS.
5A and 6). Then, in step S312, the part is side-gaged (gaged in the
X direction) to obtain an X offset value. The X offset value
detected for this bend is sent back to the planner (or the process
manager). Backgaging is then performed to align the part in the Y
direction and also to appropriately rotate the part so that it is
in the appropriate yaw position. In step S318, the bend is then
performed.
[0411] In step S320, a determination is made as to whether or not
there are more bends to be performed in the present bend sequence
being executed. If so, the process returns to step S308, where
steps S308-S313 are again performed to obtain values corresponding
to that next bend. If all of the bends have been completed, the
process proceed from step S320 to step S322, at which point the
finished part is unloaded, and a new workpiece is loaded with the
loader/uploader. Then in step S324, the part is loaded for bending
using the measured droop offset and measured X offset values that
were previously determined and forwarded to the planner. By using
such values, the bending apparatus can position the workpiece
without performing sensor-based control (or at least with a
simplified sensor-based control method) while positioning the
workpiece. This should greatly increase the speed with which the
workpiece is introduced into the die space, and reduce. Then, in
step S326, backgaging is performed to align the part in the Y and
rotation (yaw) directions. The bend is then performed in step S328,
and a determination is then made in step S330 as to whether mare
bends in the bend sequence still have to be performed. If all the
bends have been performed, the process proceeds to step S332, at
which point a determination is made as to whether more parts are to
be made. If more parts are to be made, the process returns to step
S322.
[0412] Due to the repeatability of a typical bending workstation,
such as the Amada BM100 bending workstation, the offset values only
need to-be determined by performing one or a few execution runs of
the system. Once the offset values are determined, the offset
values may be used for future batch runs of the system, and should
be considered dependable for many runs. Accordingly, the process in
FIG. 58 is illustrated as returning from step S232 to step S322 for
each new workpiece to be formed, rather than returning all the way
back to step S308 for obtaining new offset values.
[0413] 9. Costing, Scheduling, Part Design and Assembly
[0414] The present invention is described as being directed to
methods and subsystems provided in an intelligent design, planning
and manufacturing system for producing materials such as bent sheet
metal parts. The present invention may be further utilized for
performing such functions as costing (i.e., determining how much it
will cost to develop certain types of parts with a given sheet
metal bending work station), scheduling (e.g., determining how much
time it will take to perform to manufacture various parts with a
given sheet metal bending work station) and part design and
assembly. The planning system 71 of the present invention (e.g., as
disclosed in FIG. 5A) is capable of generating a complete sequence
of bends and bend-related operations which will be needed to form a
given part. The generated sequence of operations may be accompanied
by a complete plan which specifies all steps needed to execute the
bend sequence in a proper order by the sheet metal bending work
station. In generating the bend sequence, the planning system 71,
through use of experts/subplanners, will determine the consequences
of performing each bend and other accompanying operations within
the bend sequence Accordingly, without actually executing the
resulting plan generated by planning system 71, planning system 71
will have information as to what the likely amount of time it will
take to perform all of the necessary operations to manufacture the
part with the sheet metal bending work station. In addition, the
planning system S1 will be able to further confirm whether or not
the sheet metal bending work stations and available tooling are
capable of forming a particular designed part. By knowing the
consequences of performing the various operations in a given plane
planning system 71 can determine the resulting casts, and such
information may be utilized to evaluate the cast of producing a
given set of parts that form a desired assembly.
[0415] In addition, planning system 71 will be able to determine
factory scheduling with its information regarding the time needed
to complete various operations of the plan. In addition, by knowing
the limitations of producing a particular part, the amount of time
it would take to produce the part and the costs, it will be
possible to utilize such information to generate alternative part
designs which may result in less cast and less time needed for
production of the part
[0416] While planning system 71 has been described specifically as
comprising a plurality of experts, with each expert being implement
in the form of a module which is separate from bend sequence
planning module 72, planning system 71 may be implemented without
being separated into modules. Far example, planning system 71 may
be implemented as one overall operations planning module. In
addition, in the implementation shown in FIG. 8A, the language
utilized to communicate between the respective modules may be a
language other than FEL.
[0417] The modular structure shown in FIG. 5A, which utilizes a
query-based language, formalizes the interface between the modules,
resulting in an open architecture which can easily be expanded upon
by adding further modules, and/or by modifying the modules of the
planning system other modifications within the general spirit of
planning system 71 of the invention may be made. In order to
enhance the speed of operations performed by planning system 71,
such as the embodiment shown in FIG. 5A, each module (i.e., bend
sequence planner 72 and subplanners 80, 82, 84 and 85) may be
implemented on a different computer/processor
[0418] While the invention has been described with reference to
several illustrative embodiments, it is understood that the words
which have been used herein are words of description, rather than
words of limitations changes may be made, within the purview of the
appended claims without departing from the scope and the spirit of
the invention in its aspects. Although the invention has been
described herein in reference to particular means, materials, and
embodiments, it is understood that the invention is not to be
limited to the particulars disclosed herein, and that the invention
extends to all equivalent structures, methods, and uses such as are
with in the scope of the appended claims.
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