U.S. patent application number 11/102910 was filed with the patent office on 2006-10-12 for coordination in a distributed system.
This patent application is currently assigned to PALO ALTO RESEARCH CENTER INCORPORATED. Invention is credited to Lara S. Crawford, Craig Eldershaw, Markus P. J. Fromherz, Haitham A. Hindi, Kimon D. Roufas, Wheeler Ruml.
Application Number | 20060230403 11/102910 |
Document ID | / |
Family ID | 37084524 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060230403 |
Kind Code |
A1 |
Crawford; Lara S. ; et
al. |
October 12, 2006 |
Coordination in a distributed system
Abstract
Respective coordinators are spawned or activated to coordinate
activities with regard to respective tasks. Where the respective
tasks require cooperative efforts of a plurality of controllers,
the respective coordinators ensure cooperative efforts by
generating and communicating cooperative commands to the plurality
of controllers. The coordinators may act as clearinghouses for
system data, selectively requesting and relaying system information
to appropriate controllers. For example, a document processing
system activates respective coordinators for respective sheets of
print media. The respective coordinators orchestrate the
transportation of the sheets by sequentially orchestrating the
activities of sequentially selected pluralities of transportation
actuator controllers. Selected sheet position information from
sensors and/or from models maintained by the actuator controllers
may be relayed by the coordinators to selected actuator controllers
as appropriate to the sheet transportation tasks.
Inventors: |
Crawford; Lara S.; (Mountain
View, CA) ; Hindi; Haitham A.; (Menlo Park, CA)
; Fromherz; Markus P. J.; (Palo Alto, CA) ;
Eldershaw; Craig; (Mountain View, CA) ; Ruml;
Wheeler; (Palo Alto, CA) ; Roufas; Kimon D.;
(Cambridge, MA) |
Correspondence
Address: |
Patrick R. Roche;FAY, SHARPE, FAGAN, MINNICH & McKee, LLP
SEVENTH FLOOR
1100 SUPERIOR AVENUE
CLEVELAND
OH
44114-2579
US
|
Assignee: |
PALO ALTO RESEARCH CENTER
INCORPORATED
|
Family ID: |
37084524 |
Appl. No.: |
11/102910 |
Filed: |
April 8, 2005 |
Current U.S.
Class: |
718/100 |
Current CPC
Class: |
G05B 2219/32297
20130101; G05B 2219/33273 20130101; G06F 3/1296 20130101; G05B
19/41865 20130101; Y02P 90/02 20151101; G05B 2219/45187 20130101;
Y02P 90/20 20151101 |
Class at
Publication: |
718/100 |
International
Class: |
G06F 9/46 20060101
G06F009/46 |
Claims
1. A method for coordinating controllers in a distributed control
system that is operative to perform a plurality of simultaneous
tasks, the method comprising: determining a respective task of the
plurality to be performed; activating a respective coordinator in
association with the respective task, the respective coordinator
then: identifying a plurality of respective subtasks to be
performed in order to complete the respective task; identifying,
based on the identified respective subtasks, a plurality of
respective controllers, for controlling a plurality of actuators to
perform the respective subtasks; generating respective commands for
directing the performance of the respective plurality of subtasks;
communicating the respective commands to the respective controllers
as appropriate to the respective subtasks; collecting respective
progress information from at least one respective information
source; and communicating the respective progress information to
the respective controllers as appropriate to the respective
subtasks.
2. The method of claim 1 further comprising: deactivating
respective controllers as respective subtasks are determined to be
completed based on the collected respective progress information,
thereby releasing the respective controllers to execute commands
communicated from another coordinator associated with another
task.
3. The method of claim 1 further comprising: deactivating the
coordinator when the respective task is determined to be
completed.
4. The method of claim 1 further comprising: maintaining at least
one model of the respective subtasks; and deactivating at least one
of the coordinator and the respective controllers when the
respective subtasks are completed according to the at least one
model.
5. The method of claim 1 further comprising: identifying at least
one respective information source that is able to provide progress
information regarding a performance of the respective subtasks.
6. The method of claim 5 wherein identifying at least one
respective information source comprises: at least one of
identifying at least one feedback variable from at least one
controller and identifying at least one sensor.
7. The method of claim 1 further comprising: maintaining at least
one of a command model of the respective task based on the
communicated respective commands and a progress model of the
respective task based on the collected respective progress
information.
8. The method of claim 1 further comprising; maintaining a command
model of the respective task based on the communicated respective
commands; maintaining a progress model of the respective task based
on the collected respective progress information; comparing a first
indicated status of the respective task from the progress model to
a second indicated status from the command model, thereby
generating a respective task progress error value; and comparing
the respective task progress error value to a respective task
progress error limit; and performing an error task if the
respective task progress error value is beyond the respective task
progress error limit.
9. The method of claim 8 wherein performing the respective error
task comprises: generating at least one of a respective error
message identifying the respective task and describing the
respective task progress error and at least one updated command
message for correcting or compensating for a respective task
progress error associated with the respective task progress error
value.
10. A system comprising: at least one supervisory element that is
operative to generate respective task descriptions describing
respective tasks, to activate respective coordinators to be
responsible for orchestrating a completion of the respective tasks
and to communicate the respective task descriptions to the
respective coordinators; a plurality of controllers that are
operative to control a plurality of actuators according to
respective subtask descriptions received from the respective
coordinators; and a plurality of information sources that are
operative to report status information regarding respective
progress of respective tasks to the respective coordinators;
wherein the respective coordinators are operative to receive the
respective task descriptions, identify, based on the respective
task descriptions, a plurality of respective subtasks to be
performed in order to complete the task, identify, based on the
respective subtasks, a subset of the plurality of respective
controllers, for controlling a subset of the plurality of actuators
to perform the respective subtasks, generate respective commands
for performing the respective plurality of subtasks, communicate
the respective commands to the respective controllers as
appropriate to the respective subtasks, collect the respective
progress information from the respective subsets of information
sources and communicate the respective progress information to the
respective controllers as appropriate to the respective
subtasks.
11. The system of claim 10 wherein the respective coordinators are
further operative to monitor the respective progress of the
respective subtasks.
12. The system of claim 11 wherein the respective coordinators are
further operative to deactivate the respective controllers as the
subtasks are completed.
13. The system of claim 10 wherein the respective coordinators are
further operative to report the respective progress of the
respective tasks to the supervisor and wherein the supervisor is
further operative to deactivate the respective coordinators when
the respective tasks are completed.
14. The system of claim 10 wherein the at least one supervisory
element is operative to activate the respective coordinators by
spawning or instantiating the respective coordinators.
15. The system of claim 10 wherein the supervisor is operative to
activate the respective coordinators by communicating respective
task descriptions to respective idle coordinators.
16. The system of claim 10 wherein the plurality of controllers
comprises: at least one of a transport actuator controller, a nip
controller, a feeder controller, finisher controller and a marking
engine controller.
17. The system of claim 10 wherein the plurality of actuators
comprises: at least one of a xerographic marking engine actuator, a
transport actuator, a nip driver, a feeder actuator and a finisher
actuator.
18. The system of claim 10 wherein the respective coordinators are
operative to identify respective subsets of the plurality of
information sources that are able to provide progress information
regarding the performance of the respective subtasks by at least
one of identifying at least one sensor and identifying at least one
feedback variable from at least one controller of the plurality of
controllers.
19. The system of claim 11 wherein the respective coordinators are
operative to monitor the respective progress of the respective
subtasks by at least one of maintaining a command model of the task
based on the communicated respective commands and maintaining a
progress model of the task based on the respective progress
information.
20. The system of claim 11 wherein the respective coordinators are
operative to monitor the respective progress of the respective
subtasks by maintaining respective models of the respective tasks
based on the communicated respective commands and maintaining
respective progress models of the respective tasks based on the
respective progress information and wherein the respective
coordinators are further operative to compare respective first
indicated statuses of the respective tasks from the progress model
to respective second indicated statuses of the respective tasks
from the command based model, thereby generating respective task
progress error values, to compare the respective task progress
error values to respective task progress error limits and to
perform respective error tasks if the respective task progress
error values are beyond the respective error limits.
21. A method for processing a sheet in a document processing
system, the method comprising: receiving a sheet description
specifying a document processing job to be performed on the sheet;
activating a coordinator as a proxy for the sheet, the coordinator
then: identifying a plurality of respective subtasks to be
performed in order to process the sheet according to the sheet
description; identifying, based on the identified respective
subtasks, a plurality of respective controllers for controlling a
plurality of actuators to perform the respective subtasks;
generating respective commands for directing the respective
plurality of subtasks; communicating the respective commands to the
respective controllers as appropriate to the respective subtasks;
collecting respective progress information from at least one
respective information source; communicating the respective
progress information to the respective controllers as appropriate
to the respective subtasks; estimating the respective progress of
the respective subtasks; deactivating the respective controllers as
the subtasks are completed; and deactivating the coordinator when
the task is completed.
22. A document processing system comprising: a first xerographic
marking engine; a transportation system that is operative to
transport sheets of print media to and/or from the first engine,
the transportation system including a plurality of transport
actuators, at least one supervisory element that is operative to
generate respective sheet processing task descriptions describing
respective sheet processing tasks, to activate respective sheet
coordinators to be responsible for orchestrating the respective
sheet processing tasks according to the respective sheet processing
task descriptions; a plurality of respective transport controllers
that are operative to control respective sets of transport
actuators, of the plurality of transport actuators, according to
respective sheet processing subtask descriptions received from the
respective sheet coordinators; a first marking module controller
that is operative to control aspects of processing of the first
marking engine according to respective sheet processing subtask
descriptions received from the respective sheet coordinators, and a
plurality of information sources that are operative to report
status information regarding respective progress of respective
sheet processing tasks to the respective sheet coordinators;
wherein the respective sheet coordinators are operative to receive
the respective sheet processing task descriptions, identify, based
on the respective sheet processing task descriptions, a plurality
of respective sheet processing subtasks to be performed in order to
complete the respective sheet processing tasks, identify, based on
the respective sheet processing subtasks, a subset of the plurality
of respective transport controllers and the first marking module
controller, for controlling a subset of the plurality of transport
actuators and the first marking engine to perform the respective
sheet processing subtasks, identify respective subsets of the
plurality of information sources that are able to provide progress
information regarding the performance of the respective sheet
processing subtasks, generate respective commands for performing
the respective plurality of sheet processing subtasks, communicate
the respective commands to the respective transport controllers
and/or first marking engine controller as appropriate to the
respective subtasks, collect the respective progress information
from the respective subsets of information sources and communicate
the respective progress information to the respective
transportation controllers and/or first marking engine controller
as appropriate to the respective sheet processing subtasks.
23. The document processing system of claim 22 wherein the
plurality of transport controllers comprises: at least one of a nip
controller, an air jet controller, a flipper controller and a
spherical nip controller.
24. The document processing system of claim 22 further comprising:
at least a second marking engine; at least a second marking module
controller that is operative to control aspects of processing of
the at least a second marking engine according to respective sheet
processing subtask descriptions received from the respective sheet
coordinators, wherein the transportation system is further
operative to transport sheets of print media to and/or from the at
least a second marking engine; and wherein the respective sheet
coordinators are further operative to identify, based on the
respective sheet processing subtasks, at least a respective one of
the at least a second marking module controller, for controlling at
least a respective one of the at least a second marking engine to
perform the respective sheet processing subtasks, and communicate
the respective commands to at least a respective one of the at
least a second marking module controller as appropriate to the
respective subtasks.
25. A method for coordinating controllers in a distributed control
system that is operative to simultaneously perform operations on a
plurality of workpieces, the method comprising: activating a
respective coordinator for each respective workpiece, wherein each
respective coordinator encompasses knowledge regarding an itinerary
of operations to be applied to each respective workpiece, each
respective coordinator thereby: issuing respective commands to a
series of actuator controllers for directing a series of actuators
to perform respective operations on the respective workpiece
according to the itinerary; maintaining at least one respective
estimate of progress of the respective operations performed on the
respective workpiece; and deactivating the respective coordinator
when the itinerary of operations is completed.
Description
CROSS REFERENCE
[0001] The following applications, the disclosures of each being
totally incorporated herein by reference are mentioned: U.S. patent
application Ser. No. ______, filed, for Communication in a
Distributed System by Markus P. J. Fromherz, et al.
(20041213-US-NP, XERZ 2 00864); U.S. patent application Ser. No.
______, filed, for Synchronization in a Distributed System by Lara
S. Crawford, et al. (20041209-US-NP, XERZ 2 00862); and U.S. patent
application Ser. No. ______, filed, for On-The-Fly State
Synchronization in a Distributed System by Haitham A. Hindi, et al.
(20041214-US-NP, XERZ 2 00865).
BACKGROUND
[0002] There is illustrated herein in embodiments, an architecture
including methods and systems for coordinating activities in a
distributed system. For example, a distributed system may include a
collection of modules, each with its own function. The collection
of modules is interconnected to carry out a particular function or
functions. The interconnection may be physical and/or logical in
nature. Modules may be connected by a network or other
communications scheme. Communications media may include wire,
coaxial cable, fiber optics and/or radio frequency (RF)
transmissions. Embodiments will be described with reference to
document processing systems. However, embodiments of the
architecture may be beneficially applied in a wide variety of
control system environments.
[0003] Document processors include, for example, printers, copiers,
facsimile machines, finishers and devices for creating documents,
such as word processors and desk top publishers. In some instances,
document processors provide the services of two or more of these
devices. For instance, document processors that provide printing,
copying, scanning, and faxing services are available. Printers and
copiers can include finishers that staple, shrink wrap or otherwise
bind system output. Finishers may also fold or collate
documents.
[0004] In order to increase throughput, some printers and copiers
are being developed which include two or more marking engines. For
example, U.S. patent application Ser. No. 10/924,113 filed Aug. 23,
2004 by Jonas M. M. deJong, et al. for a Printing System with
Inverter Disposed for Media Velocity Buffering and Registration;
U.S. patent application Ser. No. 10/924,106 filed Aug. 23, 2004 by
Robert M. Lofthus, et al. for a Printing System with Horizontal
Highway and Single Pass Duplex; U.S. patent application Ser. No.
10/924,459 filed Aug. 23, 2004 by Barry P. Mandel, et al. for a
Parallel Printing Architecture Consisting of Containerized Image
Marking Engine Modules; U.S. patent application Ser. No. 10/860,195
filed Jun. 6, 2004 by Robert M. Lofthus, et al. for a Universal
Flexible Plural Printer to Plural Finisher Sheet Integration
System; U.S. patent application Ser. No. 10/881,619 filed Jun. 30,
2004 by Daniel G. Bobrow for a Flexible Paper Path Using
Multidirectional Path Modules; U.S. patent application Ser. No.
10/761,522 filed Jan. 21, 2004 by Barry P. Mandel, et al. for a
High Print Rate Merging and Finishing System for Parallel Printing;
U.S. patent application Ser. No. 10/785,211 filed Feb. 24, 2004 by
Robert M. Lofthus, et al. for a Universal Flexible Plural Printer
to Plural Finisher Sheet Integration System; and U.S. patent
application Ser. No. 10/917,768 filed Aug. 13, 2004 by Robert M.
Lofthus for a Parallel Printing Architecture Consisting of
Containerized Image Marking Engines and Media Feeder Modules, all
of which are incorporated herein by reference, describe aspects of
tightly integrated document processing systems including a
plurality of marking engines.
[0005] Additionally, some printers and copiers are being developed
using a hypermodular structure to increase modularity and
flexibility. These systems may possess a number of distributed
processors, sensors, and actuators. For example, U.S. patent
application Ser. No. 10/357,687 filed Feb. 4, 2003 by David K.
Biegelsen, et al., for Media Path Modules; U.S. patent application
Ser. No. 10/357,761 filed Feb. 4, 2003 by Markus P. J. Fromherz, et
al., for Frameless Media Path Modules; U.S. patent application Ser.
No. 10/740,705 filed Dec. 19, 2003 by David K. Biegelsen, et al.,
for a Flexible Director Paper Path Module; and U.S. patent
application Ser. No. 10/812,376 filed Mar. 29, 2004 by David G.
Duff, et al., for a Rotational Jam Clearance Apparatus, all of
which are incorporated herein by reference, describe aspects of
tightly integrated document processing systems including
hypermodules.
[0006] Some systems, including some document processing systems,
are based on a centralized control architecture wherein a single
computational platform controls all system actuators and receives
all system feedback information. These architectures work well
where the systems are relatively small and are of a fixed or
unchanging configuration. However, as system size increases, the
computational capabilities of a single platform can be overwhelmed.
Additionally, providing individual interfaces between the single
computational platform and each of the sensors and actuators of the
system can be impractical. Furthermore, where it is desirable to
assemble or reconfigure a system from various subcomponents, the
direct interfacing of sensors and actuators to the central platform
becomes problematic.
[0007] These factors have led to the development of systems based
on network communications. For example, U.S. Pat. No. 6,615,091 B1
to Birchenough, et al. for a Control System and Method Therefore
allegedly disclosed an embodiment of a distributed control system
including a main control coordinator, three local process station
controllers and a designated number of process module controllers,
each associated with a process module. The control system allegedly
provides a real time operating system and has a communication bus
platform provided via an Ethernet.TM. communication bus and a
second bus to connect the controllers in a distributed control
network. The Ethernet.TM. bus connects the main control coordinator
and each of the local process station controllers and a continuous
motion conveyer controller. Each of the process module controllers
are connected via the second bus to designated local process
station controllers.
[0008] In the system of Birchenough, the main controller agent
interacts with each of the process station agents, and each of the
process station agents interacts with each of the process module
agents that are assigned thereto. During normal manufacturing
operation, the main controller coordinator agent sends article
notice messages to the process station agents to notify the process
station agents of the oncoming articles of manufacture. A process
station normally will not process the article of manufacture unless
the process station agent that controls a particular process module
has received an article notice message indicating that it should do
so and the continuous feed indexer has returned a report that it is
in proper position. In response, the process station agent notifies
the designated process module agent to initiate its programmed
process operation. Once the process module has completed its
intended operation, the process module agent issues a work report
message which is sent to the process station agent. The process
station agent then broadcasts the work report message to other
process stations as well as to the main control coordinator.
[0009] It appears that in the system of Birchenough, et al., a
single entity (e.g., the main coordinator) is aware of and
maintains information regarding each task, object or workpiece
being processed by the system. This may limit the scalability of
the system. For example, as the size of the system increases, the
capabilities and/or resources of the main control coordinator (or
processor running the main control coordinator) may be
overwhelmed.
[0010] Accordingly, there has been a desire for a distributed
control architecture, including systems and methods, that provides
for scalability and reconfigurability in a modular system
environment.
BRIEF DESCRIPTION
[0011] A method for coordinating controllers in a distributed
control system that is operative to perform a plurality of
simultaneous tasks includes determining a respective task of the
plurality to be performed and activating a respective coordinator
in association with the respective task. The respective coordinator
may then identify a plurality of respective subtasks to be
performed in order to complete the respective task, identify a
plurality of respective controllers for controlling a plurality of
actuators to perform the respective subtasks, generate respective
commands for directing the performance of the respective plurality
of subtasks and communicate the respective commands to the
respective controllers as appropriate to the respective subtasks.
The respective coordinator may also identify at least one
respective information source that is able to provide progress
information regarding the performance of the respective subtasks,
collect the respective progress information from the respective at
least one information source and communicate the respective
progress information to the respective controllers as appropriate
to the respective subtasks.
[0012] The method may also include deactivating respective
controllers as respective subtasks are determined to be completed
based on the collected respective progress information, thereby
releasing the respective controllers to execute commands
communicated from another coordinator associated with another task
and/or deactivating the coordinator when the respective task is
determined to be completed. For example, one or more model may be
maintained to estimate progress of the respective subtasks and the
coordinator and/or controllers may be deactivated when the
respective subtasks are completed according to the one or more
models.
[0013] For instance the models can be based on commands the
coordinator generates and/or on progress information received from
progress information sources. The output of command based models
and progress information models can be compared to determine a task
progress error value. The error value can be compared to an error
limit. An error task, such as generating an error message or taking
corrective or compensatory action, can be performed if the error
value is beyond the error limit.
[0014] Some embodiments include a method for coordinating
controllers in a distributed control system that is operative to
simultaneously perform operations on a plurality of workpieces.
These embodiments can include activating a respective coordinator
for each respective workpiece, wherein each respective coordinator
encompasses knowledge regarding an itinerary of operations to be
applied to each respective workpiece. Each respective coordinator
may then issue respective commands to a series of actuator
controllers for directing a series of actuators to perform
respective operations on the respective workpiece according to the
itinerary, maintain at least one respective estimate of progress of
the respective operations performed on the respective workpiece and
deactivate the respective coordinator when the itinerary of
operations is completed.
[0015] A method for processing a sheet in a document processing
system can include receiving a sheet description specifying a
document processing job to be performed on the sheet and activating
a coordinator as a proxy for the sheet. The coordinator may then
identify a plurality of respective subtasks to be performed in
order to process the sheet according to the sheet description,
identify, based on the identified respective subtasks, a plurality
of respective controllers for controlling a plurality of actuators
to perform the respective subtasks, generate respective commands
for directing the respective plurality of subtasks and communicate
the respective commands to the respective controllers as
appropriate to the respective subtasks. The coordinator may also
identify at least one respective information source that is able to
provide progress information regarding the performance of the
respective subtasks, collect the respective progress information
from the respective at least one information source, communicate
the respective progress information to the respective controllers
as appropriate to the respective subtasks, estimate the respective
progress of the respective subtasks and deactivate the respective
controllers as the subtasks are completed. The coordinator may be
deactivated when the task is completed.
[0016] A system that is operative to perform embodiments of the
methods can include a plurality of controllers, at least one
supervisor element, and a plurality of information sources. The at
least one supervisory element may be operative (alone or in
combination) to generate respective task descriptions describing
respective tasks, to activate respective coordinators to be
responsible for orchestrating completion of the respective tasks
and to communicate the respective task descriptions to the
respective coordinators. The plurality of controllers may be
operative to control a plurality of actuators according to
respective subtask descriptions received from the respective
coordinators. The plurality of information sources may be operative
to report status information regarding respective progress of
respective tasks to the respective coordinators. For example, the
information sources may be sensors of the system or models or
estimators of the controllers. The respective coordinators may be
operative to receive the respective task descriptions, identify,
based on the respective task descriptions, a plurality of
respective subtasks to be performed in order to complete the task,
identify, based on the respective subtasks, a subset of the
plurality of respective controllers, for controlling a subset of
the plurality of actuators to perform the respective subtasks,
identify respective subsets of the plurality of information sources
that are able to provide progress information regarding the
performance of the respective subtasks, generate respective
commands for performing the respective plurality of subtasks,
communicate the respective commands to the respective controllers
as appropriate to the respective subtasks, collect the respective
progress information from the respective subsets of information
sources and communicate the respective progress information to the
respective controllers as appropriate to the respective
subtasks.
[0017] A document processing system embodiment can include one or
more marking engines, including, for example a xerographic marking
engine. Additionally, the system can include a transportation
system that is operative to transport sheets of print media to
and/or from the first marking engine. Some embodiments may also
include a plurality of information sources that are operative to
report status information regarding respective progress of
respective sheet processing tasks to the respective sheet
coordinators. The transportation system can include a plurality of
transport actuators, at least one supervisory element, a plurality
of respective transport controllers and a module controller. The at
least one supervisory element can be operative (alone or in
combination) to generate respective sheet processing task
descriptions describing respective sheet processing tasks and to
activate respective sheet coordinators to be responsible for
orchestrating the respective sheet processing tasks according to
the respective sheet processing task descriptions. The plurality of
respective transport controllers can be operative to control
respective sets of transport actuators, of the plurality of
transport actuators, according to respective sheet processing
subtask descriptions received from the respective sheet
coordinators. The first marking module controller may be operative
to control aspects of processing of a first marking engine
according to respective sheet processing subtask descriptions
received from the respective sheet coordinators.
[0018] For example, the respective sheet coordinators are operative
to receive the respective sheet processing task descriptions,
identify, based on the respective sheet processing task
descriptions, a plurality of respective sheet processing subtasks
to be performed in order to complete the respective sheet
processing tasks, identify, based on the respective sheet
processing subtasks, a subset of the plurality of respective
transport controllers and the first marking module controller, for
controlling a subset of the plurality of transport actuators and
the first marking engine to perform the respective sheet processing
subtasks, identify respective subsets of the plurality of
information sources that are able to provide progress information
regarding the performance of the respective sheet processing
subtasks, generate respective commands for performing the
respective plurality of sheet processing subtasks, communicate the
respective commands to the respective transport controllers and/or
first marking engine controller as appropriate to the respective
subtasks, collect the respective progress information from the
respective subsets of information sources and communicate the
respective progress information to the respective transportation
controllers and/or first marking engine controller as appropriate
to the respective sheet processing subtasks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a block diagram of a system wherein a supervisory
element has activated, spawned or instantiated a plurality of
respective coordinators that are responsible for orchestrating
respective tasks.
[0020] FIG. 2 is a flow chart outlining a method for coordinating
controllers.
[0021] FIG. 3 is a flow chart outlining a method for coordinating
controllers that includes collection and relaying of
information.
[0022] FIG. 4 is a block diagram of a document processing system
wherein a supervisory element has activated, spawned or
instantiated a plurality of respective coordinators that are
responsible for orchestrating respective document processing
tasks.
DETAILED DESCRIPTION
[0023] Referring to FIG. 1, a first system 104 embodiment includes
a plurality 106 of controllers. For example, the plurality 106 of
controllers includes a first, second, third, fourth and fifth
controller 108, 110, 112, 114, 116. The controllers may, for
example, be associated with actuators and sensors. For instance,
the first, second and third controllers 108, 110, 112 are
associated with first, second and third sets of actuators 118, 120,
122 and first, second and third sets of sensors 124, 126, 128. The
fourth controller 114 is associated with a fourth set of actuators
130. The fifth controller 116 is associated with a fourth set of
sensors 132. The actuators 118, 120, 122, 130 and sensors 124, 126,
128, 132 manipulate or sense objects in, or aspects of, respective
portions of the system 104. For example, the first set of actuators
118 and first set of sensors 124 are associated with a first
portion 140 of the system 104. The second set of actuators 120 and
the second set of sensors 126 are associated with a second portion
142 of the system 104. The third set of actuators 122 and the third
set of sensors 128 are associated with a third portion 144 of the
system 104. The fourth set of actuators 130 are associated with a
fourth portion 146 of the system 104 and the fourth set of sensors
132 are associated with a fifth portion 148 of the system 104.
[0024] Some or all of the system portions may be tightly coupled.
Tightly coupled systems or system portions are those wherein the
performance or activities of a first system portion has an effect
on the performance or activities of a second portion, even to the
point where, if the activities of the first portion and the second
portion are not coordinated, they may interfere with or disrupt
each other. For instance, in an automotive system, an
engine/transmission subsystem may be considered to be tightly
coupled with a braking subsystem because an uncoordinated
application of the braking system may interfere with or prevent the
engine/transmission system from propelling a vehicle.
[0025] In the embodiment illustrated in FIG. 1, first, second and
third elements of system dynamics 152, 154, 156 tightly couple the
second system portion 142 to the third system portion 144, tightly
couple the third system portion 144 to the fourth system portion
146 and tightly couple the fourth system portion 146 to the fifth
system portion 148. The first system portion 140 is illustrated as
having only a loose or minimal interaction with the second system
portion 142 and is not tightly coupled thereto.
[0026] The first system 104 may also include a supervisor 160 or
supervisory element. For example, the supervisory element 160 may
be a scheduler and/or a planner. The supervisor 160 determines
which tasks are to be performed or which workpieces are to be
processed. This element and/or one or more other supervisory
elements activate, spawn or instantiate a separate coordinator for
each task or workpiece. For example, a first coordinator 170 is
activated or spawned in association with a first task or workpiece,
and a second coordinator 180 is activated or spawned in association
with a second task or workpiece. The coordinators 170, 180 are
activated and initialized in such a manner as to prevent
interference between the coordinators.
[0027] For example, if the first task or workpiece and the second
task or workpiece both require the services of the first, second,
third, fourth and fifth system portions 140, 142, 144, 146, 148,
then, for example, the first coordinator 170 is activated and takes
control of the first system portion 140 by communicating with the
first controller 108. The activation of the second coordinator 180
may be delayed until the first coordinator 170 no longer requires
the services of the first system portion 140. Alternatively, the
second coordinator 180 is activated early and directed to wait or
idle until such a time as the first coordinator 170 no longer needs
the services of a first system resource (e.g., 140).
[0028] The first coordinator 170 releases the first controller 108
when the first task or workpiece no longer needs the services of
the first system portion 140. The first coordinator 170 may then
send commands requesting the services of another system resource
(e.g., the second system portion 142) for accomplishing a second
subtask. Alternatively, the first coordinator 170 may begin
requesting services from the second resource before the first
resource has completed a first subtask. In either case, the first
coordinator 170 sequentially sends commands to the controllers
(e.g., 110, 112, 114, 116) requesting services of their respective
system portions (e.g., 142, 144, 146, 148). When appropriate, the
first coordinator 170 sends coordinated commands to a plurality of
controllers. For example, if a subtask requires coordinated
activity between two or more system portions at once, then the
coordinator generates coordinated commands to two or more
controllers associated therewith.
[0029] In FIG. 1, the first system 104 embodiment is depicted at a
point in time wherein the first task or workpiece requires the
services of the fourth system portion 146 and the first coordinator
is communicating with the fourth controller 114. Proximate to
issuing commands to, or taking control of, the fourth controller
114, the third controller 112 may have been deactivated or released
from the control of the first coordinator 170. For example,
commands previously issued to the third controller 112 might have
been associated with an expiration parameter. The expiration
parameter may have been, for example, a time limit or a processing
milestone. When an event occurs that matches or surpasses the value
of the expiration parameter, the third controller 112 may be
deactivated or released from the control of the first coordinator
170.
[0030] Alternatively, the first workpiece or task may require
simultaneous services of both the third system portion 144 and the
fourth system portion 146. In that case, the first coordinator
generates and communicates coordinated or cooperative commands to
the third 112 and fourth 114 controllers.
[0031] At an appropriate point, the first coordinator will generate
commands and transmit or communicate them to the fifth controller
116 requesting services of the fifth system portion 148. If the
services of the fifth system portion are required contemporaneously
with the services of fourth 146 and/or third 144 system portions,
then the first coordinator 170 generates and communicates
cooperative commands to the fifth 116, fourth 114 and/or third 112
controllers.
[0032] FIG. 1 also illustrates the second coordinator 180 to be in
communication with the second controller 110. For example, the
second coordinator 180 is requesting services of the second system
portion 142. The first controller 108 is being, or has been,
released from serving the second coordinator 180, and the second
coordinator 180 is preparing or will prepare to take control, or
request the services of, the third system portion 144 through the
third controller 112. Since the second 142 and third system
portions are tightly coupled 152, the second controller may
generate and communicate cooperative commands to the second 110 and
third 112 controllers, thereby directing them to perform
cooperative operations or processes on the second task or
workpiece. In some instances, the first coordinator 170 and the
second coordinator 180 may communicate with each other to
facilitate coordination or for other reasons.
[0033] When the first controller 108 is released or deactivated, it
becomes available to execute commands of yet another coordinator
(not shown) which the supervisor 160 may activate, spawn or
instantiate to coordinate and orchestrate a third task or workpiece
for processing.
[0034] Referring to FIG. 2, a first method 210 for coordinating
controllers in a distributed control system can include determining
214 a task to be performed by the system and activating 218 a
coordinator (e.g., 170, 180) in association with the task. The
coordinator (e.g., 170, 180) may then identify 222 subtasks to be
performed in order to complete the task, identify 226 controllers
for performing the subtasks, generate 230 commands to direct the
controllers to perform the subtasks and communicate 234 the
commands to the controllers as appropriate to the subtasks. The
coordinator (e.g., 170, 180) may also monitor 238 the progress of
the subtasks.
[0035] Determining 214 may be done by any known task determination
method. For example, a supervisory element (e.g., 160) may
autonomously determine that a task should be performed. For
instance, sensor readings may indicate that a particular action is
required. Alternatively, the supervisory element may receive
instructions from another device or higher level supervisory
device. For example, a system user may enter commands, through a
user interface, directing that a task or series of tasks be
performed. Alternatively, commands may be received over a network
or via a wireless link from another system or remote user. The
supervisory element may translate or transform such commands into a
task description or specification and activate 218 a coordinator in
accord with the task specification.
[0036] Activating 218 a coordinator in association with the task
may include initializing a coordinator according to the task
specification. For instance, a coordinator (e.g., 170, 180) may be
embodied in software run by a computational platform such as a
microprocessor. One or more coordinators may be loaded into program
memory in an idle state. The supervisory element selects an idle
coordinator and initializes it in accord with the task
specification, thereby activating the coordinator. Alternatively,
activating 218 a coordinator may include spawning or instantiating
a coordinator by creating or loading a new process or by
referencing a program or subprogram. The spawned or instantiated
element may be initialized or loaded with the task specification or
may simply be selected for spawning or instantiation based on the
task specification. In a further alternative, the task
specification may be transmitted or otherwise communicated to the
coordinator at some point after the coordinator has been activated
218.
[0037] Identifying 222 subtasks to be performed to complete the
task and identifying 226 controllers to perform the subtasks are
related to each other and may occur simultaneously or
contemporaneously. For example, identifying subtasks may be
dependent on the capabilities of the controllers (e.g., 108, 110,
112, 114, 116) and modules or system portions (e.g., 140, 142, 144,
146, 148) associated with the controllers. For instance, if the
task specification indicates that a hole is to be drilled in a
workpiece, the coordinator (e.g., 170, 180) may have to determine
how one system portion (e.g., 140, 142, 144, 146, 148) manipulating
the piece will have to adjust its control to compensate for the
forces applied by another system portion doing the drilling.
[0038] In some embodiments, it is assumed that all task
specifications are valid. For example, a task specification
requiring that a hole be placed in a workpiece would only be
communicated to a coordinator if the system included a system
portion capable of providing the hole. In other embodiments, the
coordinator (e.g., 170, 180) checks the validity or feasibility of
a task specification and communicates an error or exception message
to the requesting entity (e.g., 160) if the specified task is not
feasible or valid. In still other embodiments, validity or
feasibility is determined by the controllers (e.g., 108, 110, 112,
114, 116) and communicated to the coordinators (e.g., 170, 180),
and from the coordinators to the supervisor (e.g., 160).
[0039] Identifying 226 the controllers or system elements to be
used to complete the task helps identify 222 the subtasks to be
performed. For instance, subtasks for the hole-stamping example
task mentioned above might include operating a motor in a transport
system so as to move the workpiece to a hole-stamping module,
operating a set of registration motors to align the workpiece in
the hole-stamping module according to a desired hole location
defined in the task specification, installing a stamp appropriate
for stamping a hole of a size defined in the task specification in
a chuck, operating actuators so as to stamp the hole in the
workpiece, operating clamps and alignment motors to hold the
workpiece in place in while the hole is being stamped, and
operating motors in a transport system to move the workpiece out of
the stamping module. Several of these subtasks would have to be
coordinated; for example, the registration operation must be
coordinated with the clamping and stamping operations.
[0040] System configuration and/or capabilities information is made
available to the coordinator (e.g., 170, 180). For example, the
coordinator may be initialized, spawned or instantiated with all
the required system configuration information. Alternatively, the
coordinator may have access to a database or may be able to query
or poll all the available controllers in a system to determine
their capabilities and, if appropriate, their relative
locations.
[0041] Generating 230 commands to direct the performance of the
subtasks is also system or embodiment dependent. In the hole
stamping example from above, the activated 218 coordinator may
generate 230 a command to direct a first controller (e.g., 108) to
drive a workpiece ejection mechanism to eject one workpiece onto a
transport mechanism. Another generated command may be for a second
controller (e.g., 110), directing the second controller to drive
the transport mechanism at a particular speed for a particular
period of time or until a sensor indicates the workpiece has
arrived at a particular position. Additional commands would be
generated 230 to load and orient the workpiece in the hole punch
module and to select, install and drive the punch as well as
transport the finished workpiece to an output device.
[0042] Communicating 234 the commands to the controllers as
appropriate to the subtasks can include any desired communication
mechanism. For example, the activated 218 coordinator (e.g., 170,
180) may communicate with the controllers (e.g., 108, 110, 112,
114, 116) over a system network, such as Ethernet.TM. or the
Controller Area Network (CAN) developed by Robert Bosch GmbH.
Information regarding the format or protocol used to communicate
with each controller (e.g., 108, 110, 112, 114, 116) is made
available to the activated 218 coordinator, either during
initialization or from some system resource such as a memory or
database.
[0043] As indicated above, the activated 218 coordinator (e.g.,
170, 180) may optionally monitor the progress of subtasks. For
example, the controller may receive subtask completion messages
from the controllers as each subtask is completed. Additionally, or
alternatively, the activated 218 coordinator may establish and
maintain a model of each subtask (or the task as a whole). For
instance, where a communicated 234 command directs a controller to
drive an actuator to move a workpiece at a given speed, the
activated 218 coordinator may maintain a command model that
estimates a position of the workpiece based on the commanded speed.
The model assumes that the command will be followed. Additionally,
or alternatively, the activated 218 coordinator may receive
progress information from one or more progress information sources.
For instance, the activated 218 coordinator (e.g., 170, 180) may
receive progress information from a controller (e.g., 108, 110,
112, 114, 116) and/or from sensors (e.g., 124, 126, 128, 132). The
activated 218 coordinator may maintain a progress model of the
subtasks (or task as a whole) based on this progress information or
may use the progress information to fine tune or update a
command-based model.
[0044] Additionally, or alternatively, progress information and/or
progress model information may be compared to output from the
command model. If the progress information or progress model
information is very different from progress estimates of the
command model (i.e., the difference is beyond an error threshold),
the activated 218 coordinator (e.g., 170, 180) may perform some
error or exception handling task. For instance, a coordinator may
send an error message or warning to a supervisory element (e.g.,
160). Additionally, or alternatively, the activated 218 coordinator
may generate 230 and communicate 234 commands to compensate for or
correct the source of the error. For example, if the progress
information indicates that processing in a first module or system
portion is occurring slower than anticipated or directed by the
commands, updated commands may be sent to a second module or system
portion indicating a delayed start time for processing at that
module or system portion. Alternatively, commands may be generated
230 and communicated 234 to the first module or system portion
directing it to process a task or workpiece at a faster rate.
[0045] The activated 218 coordinator may also act as a
clearinghouse for progress information. Such a service may serve to
conserve communication bandwidth in some systems. For example,
referring to FIG. 3, a second embodiment or method 310 for
coordinating controllers in a distributed control system includes
determining 214 a task, activating 218 a coordinator, identifying
222 subtasks, identifying 226 controllers, generating 230 commands
and communicating 234 the commands to the controllers as described
above. Additionally, the second method 310 includes identifying 314
information sources for providing subtask progress information,
collecting 318 the subtask progress information from the
information sources and communicating 322 the subtask progress
information to the controllers as appropriate to the subtasks.
[0046] Identifying 314 information sources proceeds in a manner
similar to identifying 226 controllers for performing the subtask.
System configuration and capabilities information is received from
a memory or database or is provided at activation 218 time. The
location and capabilities of available sensors (e.g., 124, 126,
128, 132) and controllers (e.g., 108, 110, 112, 114, 116) are
evaluated in light of the identified 126 subtasks. If information
from a controller or sensor that is not immediately available to an
active controller (e.g., 114, 110) would be of benefit to the
active controller in completing a subtask, that information source
is identified 314. For example, information from the third set of
sensors 128 may indicate that a workpiece is about to become
available to the fourth system portion 146. Therefore, the
coordinator 170 may request that information from one or more of
the third set of sensors 128 be delivered to the first coordinator
170. The first coordinator may then relay 322 the delivered
information to the fourth controller 114.
[0047] Collecting 318 the subtask progress information may include
receiving the information from information sources after requesting
or subscribing to the information from the identified 314
information sources. Again, the information may be received from a
network or through other communication means.
[0048] Communicating 322 the subtask progress information to the
controllers as appropriate to the subtasks may include
communicating information only when it would be useful to a
particular controller. In some embodiments, the progress
information is communicated only to those controllers for which the
information would be useful. This may reduce network traffic.
[0049] Identifying 222 subtasks, identifying 226 controllers,
generating 230 commands, and communicating 234 the commands can be
performed one time for each coordinator activation. Communicated
234 commands can include start times. Therefore, subtasks that need
to occur in the future can be requested in advance. Alternatively,
as indicated by the dashed line in FIG. 2, identifying 222
subtasks, identifying 226 controllers, generating 230 commands,
communicating 234 the commands and, where included, monitoring 238
(e.g., 314, 318), can occur on a repeated, iterative, or on-going
basis as the task or workpiece sequentially requires the services
of a new or next system portion (e.g., 140-148). In a further
alternative, the identifying 222, 226 and generating 230 commands
may occur at an initial phase and the communicating 234 of the
commands may occur as the task or workpiece requires the services
of the new or next system portion. Furthermore, generated 230
commands may be revised or replaced as needed.
[0050] Referring to FIG. 4, an embodiment of a document processing
system 404 includes a supervisory element 408, a first marking
engine 410, a second marking engine 412 and a transportation system
414.
[0051] For example, the first and second marking engines 410, 412
may be xerographic marking engines. Alternatively, one or more
marking engines of an embodiment may be of other technologies, such
as, but not limited to, ink jet marking technology.
[0052] The transportation system 414 transports print media such as
a first sheet 416 and a second sheet 418 between the first marking
engine 410 and the second marking engine 412. In the illustrated
system 404, the transportation system includes a plurality of
transport modules. For instance, the plurality of transport modules
includes a first, second, third, fourth, fifth, sixth and seventh
transport module 420, 422, 424, 426, 428, 430, 432. The system 404
may include additional modules. For example, the additional modules
may include a media or paper feeder 433, which delivers sheets of
print media or paper to one or both of the marking engines 410,
412. Additional modules (not shown) may transport print media from
either or both marking engines 410, 412 to other devices,
including, but not limited to, additional marking engines and/or
output devices such as paper trays, stackers, collators, staplers
and other binders. Furthermore, the plurality of transport modules
may form paths that branch off from the illustrated path (420, 422,
418, 424, 426, 430, 432) to transport sheets to other marking
engines (not shown) or other devices.
[0053] In the illustrated document processing system 404, each
transport module 420-432 includes transport actuators. For example,
the transport modules 420-432 include motor driven nips 434 for
driving or urging print media through the transport system 414.
Additionally, or alternatively, the modules 420-432 may include
flippers or gates for redirecting print media toward other portions
(not shown) of the transportation system 414. Furthermore, the
modules may include other kinds of transport actuators. For
instance, air jets and/or spherical nips may be included in the
transport modules (e.g., 420-432). For the purposes of
illustration, the modules of FIG. 4 are associated with the nips
434 depicted to their left. The transport modules 420-432 of the
document processor system 404 include sensors. For instance, the
sensors may be sheet presence or position sensors. As illustrated,
each module 420-432 includes a left side sensor 436 and a right
side sensor 438.
[0054] Each transport module 420-432 also includes or is associated
with a respective module controller 440, 442, 444, 446, 448, 450,
452. For example, the module controllers 440-452 control the
actions of the transport actuators of their respective modules
420-432 and receive and relay information from their respective
sensors 436, 438.
[0055] The supervisory element 408 is operative to generate (e.g.,
214) sheet processing task descriptions or itineraries describing
respective sheet processing tasks, to activate (e.g., 218)
respective sheet coordinators (e.g., a first sheet coordinator 460
and a second sheet coordinator 464) and to communicate the
respective sheet processing task descriptions to the respective
sheet coordinators (e.g., 460, 464). For example, the supervisory
element 408 receives a job description 470. The job description 470
may include descriptions of sheets or pages. The descriptions may
include images, or references to images stored elsewhere and
indications as to an order in which the images are to appear on
sheets of print media. For example, the job description 470
includes page description language describing text and fonts and
graphic items as well as their location on particular pages of a
document. The supervisory element 408 activates, instantiates or
spawns (e.g., 218) a sheet coordinator for each sheet or page (a
sheet may have two sides and may, therefore, comprise two pages).
The supervisory element 408 analyses the job description 470 and
may schedule or plan operations to create the document described in
the job description 470. In so doing, the supervisory element 408
generates respective sheet processing task descriptions or
itineraries for the transportation and processing of sheets between
system resources.
[0056] For instance, regarding the transportation of a sheet
between system resources, an example itinerary or sheet processing
task description may have the following form:
[0057] Itin 1 1 11
[0058] feeder1 feed 19.544
[0059] me1 print image27 20.201
[0060] m1 left2right 23.341
[0061] m2 left2right 23.495
[0062] m3 left2right 23.625
[0063] m4 left2right 23.755
[0064] m5 left2right 23.885
[0065] m6 left2right 24.015
[0066] m7 left2right 24.145
[0067] me2 print image28 24.275
[0068] finisher1 stack 27.415
[0069] The first line is, for example, an itinerary or sheet
processing task description identifier. The rest of the itinerary
specifies, for example, that a component named feeder1 (e.g., 433)
should feed a sheet at time 19.544, then a component named me1
should execute a print action on an image named image27 at a later
time, then a component named m1 should execute an action (move the
sheet left to right) at a later time, and so on.
[0070] The respective sheet coordinators (e.g., 460, 464) are
operative to receive the respective sheet processing task
descriptions or itineraries and, based on those respective
descriptions, identify (e.g., 222) a plurality of respective sheet
processing subtasks to be performed in order to complete the
respective sheet processing tasks, identify (e.g., 226) respective
controllers for controlling respective process actuators to perform
the respective sheet processing subtasks, generate (e.g., 230)
respective commands for performing the respective sheet processing
subtasks and communicating (e.g., 234) the respective commands to
the respective module controllers as appropriate to the respective
subtasks. Additionally, the respective sheet coordinators (e.g.,
460, 464) may identify (e.g., 314) respective information sources
that are able to provide progress information regarding the
performance of the respective subtasks, collect (e.g., 318) the
respective progress information from the respective subsets of
information sources and communicate (e.g., 322) the respective
progress information to the respective module controllers as
appropriate to the respective sheet processing subtasks.
[0071] For example, the information sources may include the sensors
436, 438. Additionally, or alternatively, the module controllers
themselves may maintain models or estimators of the progress of
respective subtasks. Such models are referred to as sheet observer
models. In this regard, the module controllers or the estimates or
models of the module controllers may be considered information
sources.
[0072] For instance, in the illustrated document processing
embodiment 404, subtasks for a first sheet may have included
matching a speed of nips 434 of the first module 420 to a speed of
a sheet exiting the first marking engine 410 and receiving the
first sheet 416 therefrom. A second subtask might have been for
nips 434 of the second module 422 to match the speed of the first
sheet 416 as it exited the first module 420. A subtask of the third
module 424 may have been to match the speed of the first sheet 416
as a leading edge thereof exited the second module 422. Yet another
subtask may have been for the nips 434 of the first, second and
third modules 420, 422, 424 to accelerate or to begin to accelerate
the first sheet 416 to a higher transportation system 414 transport
speed.
[0073] Additional subtasks associated with the fourth, fifth and
sixth modules 426, 428, 430 may have included matching associated
nip 434 speeds to the speed of the first sheet 416 as it entered
each module 426, 428, 430 and/or continuing to accelerate the sheet
416.
[0074] The transfer or movement of a sheet from module to module
must be done in a coordinated manner. In the document processing
embodiment 404, the modules 410, 412, 420-433 are tightly coupled
by their relationship to a sheet. For example, at any given point
in time, a plurality of modules may be in contact with the same
sheet. If the nips 434 of modules contacting a sheet are driven at
different speeds or with different rates of acceleration or
deceleration, the sheet (e.g., 416, 418) may be damaged or
distorted in a manner that causes a jam in the transportation
system 414 or system 404 as a whole. The sheet coordinators (e.g.,
460, 464) ensure cooperative or coordinated actuation of the
actuators or modules (e.g., 410, 412, 420-433). For example, at the
instant depicted in FIG. 4, the first sheet 416 is in contact with
portions of the fourth, fifth and sixth modules 426, 428, 430. The
first sheet coordinator 460 is shown in communication with the
fourth, fifth, sixth and seventh module controllers 446-452. For
example, the first sheet coordinator 460 may be sending commands to
the fifth and sixth module controllers 448, 450 that result in the
fifth and sixth modules 428, 430 driving the first sheet 416 in a
cooperative manner. For instance, the fifth and sixth module
controllers 448, 450 may be directed to begin decelerating the
first sheet 416. Additionally, the first sheet coordinator 460 may
be requesting or receiving sensor information or sheet observer
model information from the fourth module controller 446. For
instance, the first sheet coordinator 460 may be requesting to be
notified when a trailing edge of the first sheet 416 passes the
left sensor 436 of the fourth module. Additionally, the first sheet
coordinator 460 may be asking or receiving sensor information from
the sixth module 430. For instance, the first sheet coordinator 460
may be requesting to be notified when a leading edge of the first
sheet 416 passes or enters a field of view of the right sensor 438
of the sixth module.
[0075] This sensor information may be relayed by the sheet
coordinator to the seventh module controller 452. Additionally, or
alternatively, the first sheet coordinator 460 may update a model,
such as a world observer model of the task or of the subtasks based
on the information from the information sources or sensors (e.g.,
436, 438).
[0076] In addition to possibly relaying sensor information, the
first sheet coordinator 460 may be sending commands directing the
seventh module controller 452 to prepare the seventh module 432 to
receive the first sheet 416. For instance, the seventh module
controller 452 may be directed to drive nips 434 of the seventh
module 432 at a speed compatible with the speed of the first sheet
416 as the leading edge thereof exits the sixth module 430.
Additionally, the fifth, sixth and seventh module controllers 448,
450, 452 may be receiving commands directing that they begin
decelerating the first sheet in preparation for its entry into the
second marking engine 412. The first sheet coordinator 460 may also
be transmitting commands to the fourth module controller 446
releasing it from service or subtasks related to the transportation
of the first sheet 416. Alternatively, prior commands may have
included an expiration event, such as a time limit or sensor
reading, the occurrence of which automatically deactivates or
releases the fourth module controller from services related to the
first sheet 416.
[0077] At a point later in time than the instant depicted in FIG.
4, the first sheet 416 may enter the second marking engine 412 for
processing. For example, the second marking engine may be used to
print an image on a second side of the first sheet or may apply
color markings that the first marking engine 410 did not apply. At
that later point in time, the first sheet will no longer be in
contact with the fourth module 426 and the trailing edge of the
first sheet will be about to exit the fifth module 428. The fourth
module controller 446 may have already been released (as described
above) from subtasks associated with processing the first sheet 416
and may have begun performing subtasks associated with processing
the second sheet 418. The fifth module controller 448 may be about
to be similarly released.
[0078] The sixth and seventh transport modules 430, 432 and the
second marking engine (or module) 412 are likely all in contact
with the first sheet 416. Therefore, the first coordinator 460 is
generating or has generated (e.g., 230) and will communicate or has
communicated (e.g., 234) commands for the sixth and seventh
transport modules 430, 432 and the second marking engine 412 or a
marking engine module controller 474. The commands may be
cooperative in nature. For example, the transport modules 430, 432
may be directed to slow the sheet to a speed compatible with
capabilities of the marking engine 412. Additionally, commands for
the second marking engine controller 474 may direct it to control
the second marking engine 412 to accept the first sheet at the
compatible speed and to place specified marks on portions of the
first sheet 416. As the first sheet 416 continues into the second
marking engine 412, the sixth and seventh module controllers 450,
452 will be released from subtasks associated with the first sheet
416, or deactivated. Eventually, the first sheet 416 will exit the
second marking engine or module 412 and be delivered to other
modules (e.g., transport modules, finishers, stackers and/or other
print engines). The first coordinator will continue to send
appropriate commands to the subsequent modules, relay progress
information and release or deactivate controllers, in the
sequential manner described above, until the task described in the
task description, or itinerary, received when the first coordinator
460 was activated 218 is completed. When the task is completed, the
first coordinator 460 may be deactivated.
[0079] Similar processing occurs with regard to the second 464 and
subsequent (not shown) coordinators and second 418 and subsequent
(not shown) sheets. For example, as depicted in FIG. 4, the second
sheet 418 is within the first, second and third modules 420, 422,
424. The second sheet coordinator 464 is depicted as in
communication with the first, second, third and fourth module
controllers 440-446. For example, the second sheet coordinator 464
may be directing the second and third module controllers 442, 444
to drive the second sheet 418 at the same speed and/or with the
same acceleration, receiving or requesting sensor information from
the sensors 436, 438 of the first module 420 and/or the third
module 424, releasing the first module controller 440 from tasks
associated with transporting the second sheet 418, and/or directing
the fourth module controller 446 to prepare to receive the second
sheet 418 by driving nips 434 of the fourth module 426 at a speed
appropriate to, or compatible with, a speed of the second sheet
418, as a leading edge thereof exits the third module 424 and
enters the fourth module 426. As the sheets 416, 418 are
transported through the system 404, the sheet coordinators
deactivate or release module controllers no longer processing their
respective sheets and send commands to downstream controllers
preparing them to receive their respective sheets.
[0080] Prior to the moment depicted in FIG. 4., the first
coordinator generated 230 and sent 234 commands to a feeder module
controller 478 directing it to control the feeder 433 to deliver
the first sheet 416 to the first marking engine (or transport
modules on a path thereto (not shown)) and may have generated 230
and sent 234 commands to a first marking module controller 482
instructing it to control the first marking engine 410 to place
particular marks on portions of the first sheet 416 and deliver the
first sheet 416 to the first transport module 420. As mentioned
above, when their respective tasks, as described in their
respective sheet processing task descriptions or itineraries, are
completed, the respective sheet coordinators (e.g., 460, 464) are
deactivated. For instance, they are de-instantiated or placed in an
idle mode to await re-initialization with information from a new
sheet processing task description.
[0081] Supervisory element and module controller embodiments may be
made substantially in software stored in computer storage devices,
such as memory elements, and run by computational platforms, such
as microprocessors, microcontrollers, and digital signal
processors. Alternatively, supervisory elements and module
controllers may be embodied in various combinations of hardware and
software.
[0082] In a prototype, the transport module controllers were each
embodied in separate computational platforms associated with
transport modules on a one-to-one basis. Each transport module
included a plurality of nips and flippers. Marking engines are
known to include their own controllers. The supervisory element 408
was run on one computational platform and activated or spawned
sheet coordinators (e.g., 460, 464) were software elements run on
another computational platform. However, embodiments wherein the
sheet coordinators, or activating data associated with the sheet
coordinators, move from module controller to module controller
(e.g., 440-452, 474-482) as their respective sheets move from
module to module (e.g., 433, 410, 420-432, 412), are
contemplated.
[0083] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims.
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