U.S. patent application number 15/793125 was filed with the patent office on 2018-03-01 for robot, robot system, and robot control device.
The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Yasuhiro SHIMODAIRA.
Application Number | 20180059637 15/793125 |
Document ID | / |
Family ID | 53007607 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180059637 |
Kind Code |
A1 |
SHIMODAIRA; Yasuhiro |
March 1, 2018 |
ROBOT, ROBOT SYSTEM, AND ROBOT CONTROL DEVICE
Abstract
A robot includes a robot arm, a force sensor, and a control unit
configured to control the operation of the robot art. The control
unit initializes the force sensor while the robot arm is moving at
uniform speed. It is preferable that the control unit initializes
the force sensor while the robot arm is moving at the uniform speed
and the amplitude of a detection value of the force sensor is
smaller than a threshold.
Inventors: |
SHIMODAIRA; Yasuhiro;
(Matsumoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
53007607 |
Appl. No.: |
15/793125 |
Filed: |
October 25, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15131483 |
Apr 18, 2016 |
9829878 |
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15793125 |
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14529364 |
Oct 31, 2014 |
9342066 |
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15131483 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B 2219/39058
20130101; G05B 2219/45064 20130101; Y10S 901/41 20130101; B25J
13/085 20130101; Y10S 901/31 20130101; G05B 19/401 20130101; B25J
9/1694 20130101; Y10S 901/02 20130101; G05B 2219/39529 20130101;
Y10S 901/46 20130101; B25J 9/1692 20130101; G05B 2219/45058
20130101; G05B 2219/40599 20130101 |
International
Class: |
G05B 19/401 20060101
G05B019/401; B25J 13/08 20060101 B25J013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2013 |
JP |
2013-228813 |
Mar 24, 2014 |
JP |
2014-059822 |
Claims
1. A control device comprising: a processor that is configured to
execute computer-executable instructions so as to control a robot
that includes a robot arm to which a hand is attached and a force
detector, wherein the processor is configured to bring a machining
target gripped by the hand into contact with a fixed machining tool
fixed to machine the machining target.
2. The control device according to claim 1, wherein the processor
is configured to maintain a contact state in which the machining
target and the machining tool are in contact with each other so
that an output value of the force detector is at a predetermined
value set in advance.
3. The control device according to claim 1, wherein the machining
target is a workpiece gripped by the hand, the machining tool is a
rotating tool, and the machining target is brought into contact
with a polishing tool attached to a rotating shaft of the rotating
tool.
4. The control device according to claim 2, wherein the machining
target is a workpiece gripped by the hand, the machining tool is a
rotating tool, and the machining target is brought into contact
with a polishing tool attached to a rotating shaft of the rotating
tool.
5. The control device according to claim 3, wherein the machining
target is a workpiece gripped by the hand, the machining tool is a
rotating tool, and the machining target is brought into contact
with a polishing tool attached to a rotating shaft of the rotating
tool.
6. A robot that is controlled by the control device according to
claim 1.
7. A robot that is controlled by the control device according to
claim 2.
8. A robot that is controlled by the control device according to
claim 3.
9. A robot that is controlled by the control device according to
claim 4.
10. A robot that is controlled by the control device according to
claim 5.
11. A robot system comprising: the control device according to
claim 1; and a robot that is controlled by the control device and
includes the robot arm to which the hand is attached and the force
detector.
12. A robot system comprising: the control device according to
claim 2; and a robot that is controlled by the control device and
includes the robot arm to which the hand is attached and the force
detector.
13. A robot system comprising: the control device according to
claim 3; and a robot that is controlled by the control device and
includes the robot arm to which the hand is attached and the force
detector.
14. A robot system comprising: the control device according to
claim 4; and a robot that is controlled by the control device and
includes the robot arm to which the hand is attached and the force
detector.
15. A robot system comprising: the control device according to
claim 5; and a robot that is controlled by the control device and
includes the robot arm to which the hand is attached and the force
detector.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional patent application of U.S. application
Ser. No. 15/131,483, filed Apr. 18, 2016, which is a continuation
patent application of U.S. application Ser. No. 14/529,364, filed
Oct. 31, 2014, now U.S. Pat. No. 9,342,066, issued May 17, 2016,
which claims priority to Japanese Patent Application No.
2013-228813 filed Nov. 1, 2013 and Japanese Patent Application No.
2014-059822, filed Mar. 24, 2014. The entire disclosures of these
applications are expressly incorporated by reference herein.
BACKGROUND
1. Technical Field
[0002] The present invention relates to a robot, a robot system,
and a robot control device.
2. Related Art
[0003] A robot including a robot arm has been known. A plurality of
arm members are coupled via joint sections in the robot arm. For
example, a hand is attached to the arm member on the most distal
end side as an end effector. The joint sections are driven by
motors. The arm members turn according to the driving of the joint
sections. The robot performs work for, for example, gripping a
target with the hand, moving the target to a predetermined place,
and inserting the target into an opening.
[0004] A force sensor is provided between the arm member on the
most distal end side and the hand. In performing the work, the
robot detects a force and a moment with the force sensor and
performs impedance control (force control) on the basis of a
detection result of the force sensor.
[0005] In the force sensor, accuracy of force detection is
deteriorated because of a temperature change, an output drift due
to a leak current of a circuit, and the like. Therefore, in
performing the work, the robot performs zero-point correction
(initialization) of the force sensor (see, for example,
JP-A-2009-23047 (Patent Literature 1)). According to the zero-point
correction of the force sensor, it is possible to improve the
accuracy of the force detection.
[0006] JP-A-2005-81477 (Patent Literature 2) discloses, as a robot
system, an automatic polishing apparatus that performs polishing by
moving a polishing tool (a Leutor). The automatic polishing
apparatus performs operation for measuring, with a polishing force
measuring device (a force sensor), a polishing force applied to the
polishing tool, moving the polishing tool on the basis of the
measured polishing force, and keeping the polishing force fixed
(see paragraph "0014" and FIG. 4 of Patent Literature 2).
[0007] However, in the robot in the past, as shown in FIG. 17, as
work performed using the force sensor, when the robot arm is moved
from a first position to a second position, the target is inserted
into the opening, and thereafter the robot arm is moved to a third
position, the zero-point correction of the force sensor needs to be
performed in a state in which the robot arm is stopped in the first
position. Consequently, a cycle time increases in the work
performed using the force sensor.
[0008] In the robot system described in Patent Literature 2, since
the force sensor is present on the Leutor side where a rotating
shaft rotates at high speed, a vibration component (noise) caused
by the high-speed rotation of the Leutor is superimposed on the
polishing force detected by the force sensor. In the case of the
rotating polishing tool such as the Leutor, reaction due to a gyro
effect, which occurs when an object having an inertial moment is
moved, also occurs. Therefore, the polishing tool is moved on the
basis of an output value of the force sensor affected by the noise
and the reaction is moved. Therefore, the control for keeping the
polishing force (the force applied to the target) fixed cannot be
accurately performed.
SUMMARY
[0009] An advantage of some aspects of the invention is to solve at
least a part of the problems described above, and the invention can
be implemented as the following application examples or
aspects.
Application Example 1
[0010] A robot according to this application example includes: a
robot arm; a force sensor; and a control unit configured to control
the operation of the robot art. The control unit initializes the
force sensor while the robot arm is moving at uniform speed.
[0011] With this configuration, when work is performed, the
initialization of the force sensor is performed during the movement
of the robot arm. Therefore, it is possible to reduce a cycle time
in work performed using the force sensor.
Application Example 2
[0012] In the robot according to the application example described
above, it is preferable that the control unit initializes the force
sensor while the robot arm is moving at the uniform speed and the
amplitude of a detection value of the force sensor is smaller than
a threshold.
[0013] With this configuration, it is possible to properly
initialize the force sensor.
Application Example 3
[0014] In the robot according to the application example described
above, it is preferable that the control unit initializes the force
sensor while the robot arm is moving at the uniform speed and when
the amplitude of the detection value of the force sensor is smaller
than the threshold.
[0015] With this configuration, it is possible to properly
initialize the force sensor and further reduce the cycle time.
Application Example 4
[0016] In the robot according to the application example described
above, it is preferable that the threshold is equal to or smaller
than 10 N.
[0017] With this configuration, it is possible to properly
initialize the force sensor.
Application Example 5
[0018] In the robot according to the application example described
above, it is preferable that the force sensor is provided in the
robot arm, and the control unit determines on the basis of speed of
apart of the robot arm in which the force sensor is provided
whether the robot arm is moving at the uniform speed.
[0019] With this configuration, it is possible to properly
initialize the force sensor.
Application Example 6
[0020] In the robot according to the application example described
above, it is preferable that the control unit determines on the
basis of speed of the distal end section of the robot arm whether
the robot arm is moving at uniform speed.
[0021] With this configuration, it is possible to properly
initialize the force sensor.
Application Example 7
[0022] A robot system according to this application example
includes: a robot including a robot arm and a force sensor; and a
control unit configured to control the operation of the robot arm.
The control unit initializes the force sensor while the robot arm
is moving at uniform speed.
[0023] With this configuration, when work is performed, the
initialization of the force sensor is performed during the movement
of the robot arm. Therefore, it is possible to reduce a cycle time
in work performed using the force sensor.
Application Example 8
[0024] A robot control device according to this application example
is a robot control device that controls the operation of a robot
including a robot arm and a force sensor. The robot control device
initializes the force sensor while the robot arm is moving at
uniform speed.
[0025] With this configuration, when work is performed, the
initialization of the force sensor is performed during the movement
of the robot arm. Therefore, it is possible to reduce a cycle time
in work performed using the force sensor.
[0026] An aspect of the invention is directed to a robot including:
a force sensor; and an arm including a gripping section. The robot
brings a machining target gripped by the gripping section into
contact with a fixed machining tool to machine the machining
target.
[0027] With this configuration, in the robot, the force sensor is
provided in the robot itself rather than on the machining tool
side. Consequently, the robot keeps a contact state of the
machining target and the machining tool according to an output
value of the force sensor on which noise is not superimposed.
Therefore, it is possible to provide the robot that can accurately
keep a force applied to the machining target fixed.
[0028] In the aspect of the invention, to set the output value of
the force sensor to a predetermined value set in advance, the robot
may keep a state in which the machining target and the machining
tool are set in contact with each other.
[0029] With this configuration, to set the output value of the
force sensor to the predetermined value set in advance, control for
keeping the state in which the machining target and the machining
tool are set in contact with each other is performed. Consequently,
it is possible to provide the robot that can accurately keep the
force applied to the machining target fixed.
[0030] In the aspect of the invention, in the robot, the machining
target may be a workpiece gripped by the gripping section of the
robot. The machining tool may be a rotating tool. The machining
target may be brought into contact with a polishing tool attached
to a rotating shaft of the rotating tool.
[0031] With this configuration, control for keeping a state in
which the workpiece and the polishing tool are set in contact with
each other is performed. Consequently, it is possible to provide a
robot that can accurately keep a polishing force applied to the
workpiece from the polishing tool fixed. For example, a polishing
amount can be adjusted by changing the predetermined value set in
advance. Therefore, when a character is drawn on the workpiece, it
is possible to adjust shading of the character.
[0032] Another aspect of the invention is directed to a robot
system including: a robot including a force sensor and an arm
including a gripping section; and a control device. The control
device brings a machining target gripped by the gripping section
into contact with a fixed machining tool to machine the machining
target.
[0033] With this configuration, in the robot, the force sensor is
provided in the robot itself rather than on the machining tool
side. Consequently, the control device keeps a contact state of the
machining target and the machining tool according to an output
value of the force sensor on which noise is not superimposed.
Therefore, it is possible to provide the robot system that can
accurately keep a force applied to the machining target fixed.
[0034] Still another aspect of the invention is directed to a
control device that causes a robot including a force sensor and an
arm including a gripping section to bring a machining target
gripped by the gripping section into contact with a fixed machining
tool to machine the machining target.
[0035] With this configuration, in the robot, the force sensor is
provided in the robot itself rather than on the machining tool
side. Consequently, the control device keeps a contact state of the
machining target and the machining tool according to an output
value of the force sensor on which noise is not superimposed.
Therefore, it is possible to provide the control device that can
accurately keep a force applied to the machining target fixed.
[0036] According to the aspects explained above, the force sensor
is provided in the robot itself rather than on the machining tool
side. Therefore, the robot keeps a contact state of the machining
target and the machining tool according to an output value of the
force sensor on which noise is not superimposed. Consequently, it
is possible to provide the robot, the robot system, and the control
device that can accurately keep a force applied to the machining
target fixed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0038] FIG. 1 is a perspective view showing a robot according to a
first embodiment of the invention.
[0039] FIG. 2 is a schematic diagram of the robot shown in FIG.
1.
[0040] FIG. 3 is a block diagram of a main part of the robot shown
in FIG. 1.
[0041] FIG. 4 is a circuit diagram showing the configuration of a
part of a force sensor of the robot shown in FIG. 1.
[0042] FIG. 5 is a timing chart showing the operation of the robot
shown in FIG. 1 in a period including a period of initialization of
a force sensor.
[0043] FIG. 6 is a flowchart for explaining a control operation of
a robot control device of the robot shown in FIG. 1.
[0044] FIG. 7 is a diagram for explaining an operation in a
workpiece of the robot shown in FIG. 1.
[0045] FIG. 8 is a diagram for explaining the operation in the
workpiece of the robot shown in FIG. 1.
[0046] FIG. 9 is a diagram for explaining the operation in the
workpiece of the robot shown in FIG. 1.
[0047] FIG. 10 is a diagram for explaining a robot according to the
workpiece of the robot shown in FIG. 1.
[0048] FIG. 11 is a schematic diagram showing a robot according to
a second embodiment of the invention.
[0049] FIG. 12 is a perspective view showing a robot system
according to a third embodiment of the invention.
[0050] FIG. 13 is a diagram showing a schematic configuration
example of a robot system according to a fourth embodiment of the
invention.
[0051] FIG. 14 is a diagram for explaining a specific example of
the robot system shown in FIG. 13.
[0052] FIG. 15 is a flowchart for explaining processing of control
by a robot control device shown in FIG. 13.
[0053] FIG. 16 is a diagram showing a schematic configuration
example of a robot system according to a fifth embodiment of the
invention.
[0054] FIG. 17 is a timing chart showing the operation of a robot
in the past in a period including a period of initialization of a
force sensor.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0055] A robot, a robot system, and a robot control device
according to preferred embodiments of the invention are explained
in detail below with reference to the drawings.
First Embodiment (Robot)
[0056] FIG. 1 is a perspective view of a robot according to a first
embodiment of the invention viewed from the front side. FIG. 2 is a
schematic diagram of the robot shown in FIG. 1. FIG. 3 is a block
diagram of a main part of the robot shown in FIG. 1. FIG. 4 is a
circuit diagram showing the configuration of a part of a force
sensor of the robot shown in FIG. 1. FIG. 5 is a timing chart
showing the operation of the robot shown in FIG. 1 in a period
including a period of initialization of a force sensor. FIG. 6 is a
flowchart for explaining a control operation of a robot control
device of the robot shown in FIG. 1. FIGS. 7 to 10 are diagrams for
explaining an operation in work of the robot shown in FIG. 1.
[0057] Note that, in the following explanation, for convenience of
explanation, the upper side in FIGS. 1, 2, and 7 to 10 is referred
to as "up" or "upward" and the lower side in the figures is
referred to as "down" or "downward". The base side in FIGS. 1, 2,
and 7 to 10 is referred to as "proximal end" and the opposite side
of the base side is referred to as "distal end".
[0058] In FIGS. 7 to 10, to prevent the figures from being
complicated, in a robot 1, only members necessary for explanation,
that is, a second arm member 13, a third arm member 14, a wrist 16
(a fifth arm member 17), and a hand 91 are shown.
[0059] The robot (an industrial robot) 1 shown in FIGS. 1 to 3 can
be used in a manufacturing process for manufacturing, for example,
a precision instrument such as a wristwatch. The robot 1 includes a
robot main body (a main body section) 10 and a robot control device
(a control unit) 20 that controls the operation of the robot main
body 10 (the robot 1). The robot control device 20 is incorporated
in the robot 1. The robot main body 10 and the robot control device
20 are electrically connected. The position of the robot control
device 20 in the robot 1 is not particularly limited. However, in
the configuration shown in the figure, the robot control device 20
is set in a base 11. The robot control device 20 can be configured
by, for example, a personal computer (PC) incorporating a CPU
(Central Processing Unit). Note that the robot control device 20 is
explained in detail below.
[0060] The robot main body 10 includes the base (a supporting
section) 11 and a robot arm 5. The robot arm 5 includes six arm
members (arm sections) 12, 13, 14, 15, 17, and 18 and six driving
sources 401, 402, 403, 404, 405, and 406. A wrist 16 is configured
by the arm member 17 and the arm member 18. An end effector (see
FIG. 2) such as the hand 91 can be attached to the distal end of
the arm member 18. That is, the robot 1 is a vertical multi-joint
(six-axis) robot in which the base 11, the arm members 12, 13, 14,
15, 17, and 18, and the wrist 16 are coupled in this order from the
proximal end side to the distal end side. Note that, in the
following explanation, the arm member 12 is also referred to as
"first arm member", the arm member 13 is also referred to as
"second arm ember", the arm member 14 is also referred to as "third
arm member", the arm member 15 is also referred to as "fourth arm
member", the arm member 17 is also referred to as "fifth arm
member", and the arm member 18 is also referred to as "sixth arm
member". The driving source 401 is also referred to as "first
driving source", the driving source 402 is also referred to as
"second driving source", the driving source 403 is also referred to
as "third driving source", the driving source 404 is also referred
to as "fourth driving source", the driving source 405 is also
referred to as "fifth driving source", and the driving source 406
is also referred to as "sixth driving source".
[0061] The arm members 12 to 15 and the wrist 16 are supported
displaceably with respect to the base 11 independently from one
another. The lengths of the arm members 12 to 15 and the wrist 16
are not particularly limited. However, in the configuration shown
in the figure, the lengths of the first arm member 12, the second
arm member 13, and the fourth arm member 15 are set larger than the
lengths of the third arm member 14 and the wrist 16.
[0062] As shown in FIGS. 1 and 2, the base 11 and the first arm
member 12 are coupled via a joint 171. The joint 171 includes a
mechanism for supporting the first arm member 12 to be turnable
with respect to the base 11 to which the first arm member 12 is
coupled. Consequently, the first arm member 12 is configured to be
turnable with respect to the base 11 about a first turning axis O1
parallel to the vertical direction. The first turning axis O1
coincides with the normal of the upper surface of a floor 101,
which is a setting surface of the base 11. The turning about the
first turning axis O1 is performed according to driving by the
first driving source 401 including a motor 401M. The first driving
source 401 is driven by the motor 401M and a cable (not shown in
the figures). The motor 401M is controlled by the robot control
device 20 via a motor driver 301 electrically connected to the
motor 401M (see FIG. 3). Note that the first driving source 401 may
be configured to transmit a driving force from the motor 401M with
a reduction gear (not shown in the figures) provided together with
the motor 401M. The reduction gear may be omitted.
[0063] The first arm member 12 and the second arm member 13 are
coupled via a joint 172. The joint 172 includes a mechanism for
supporting one of the first arm member 12 and the second arm member
13, which are coupled to each other, to be turnable with respect to
the other. Consequently, the second arm member 13 is configured to
be turnable with respect to the first arm member 12 about a second
turning axis O2 parallel to the horizontal direction. The second
turning axis O2 is orthogonal to the first turning axis O1. The
turning about the second turning axis O2 is performed according to
driving by the second driving source 402 including a motor 402M.
The second driving source 402 is driven by the motor 402M and a
cable (not shown in the figures). The motor 402M is controlled by
the robot control device 20 via a motor driver 302 electrically
connected to the motor 402M (see FIG. 3). Note that the second
driving source 402 may be configured to transmit a driving force
from the motor 402M with a reduction gear (not shown in the
figures) provided together with the motor 402M. The reduction gear
may be omitted. The second turning axis O2 may be parallel to an
axis orthogonal to the first turning axis O1.
[0064] The second arm member 13 and the third arm member 14 are
coupled via a joint 173. The joint 173 includes a mechanism for
supporting one of the second arm member 13 and the third arm member
14, which are coupled to each other, to be turnable with respect to
the other. Consequently, the third arm member 14 is configured to
be turnable with respect to the second arm member 13 about a third
turning axis O3 parallel to the horizontal direction. The third
turning axis O3 is parallel to the second turning axis O2. The
turning about the third turning axis O3 is performed according to
driving by the third driving source 403. The third driving source
403 is driven by a motor 403M and a cable (not shown in the
figures). The motor 403M is controlled by the robot control device
20 via a motor driver 303 electrically connected to the motor 403M
(see FIG. 3). Note that the third driving source 403 may be
configured to transmit a driving force from the motor 403M with a
reduction gear (not shown in the figures) provided together with
the motor 403M. The reduction gear may be omitted.
[0065] The third arm member 14 and the fourth arm member 15 are
coupled via a joint 174. The joint 174 includes a mechanism for
supporting one of the third arm member 14 and the fourth arm member
15, which are coupled to each other, to be turnable with respect to
the other. Consequently, the fourth arm member 15 is configured to
be turnable with respect to the third arm member 14 (the base 11)
about a fourth turning axis O4 parallel to the center axis
direction of the third arm member 14. The turning about the fourth
turning axis O4 is performed according to driving by the fourth
driving source 404. The fourth driving source 404 is driven by a
motor 404M and a cable (not shown in the figures). The motor 404M
is controlled by the robot control device 20 via a motor driver 304
electrically connected to the motor 404M (see FIG. 3). Note that
the fourth driving source 404 may be configured to transmit a
driving force from the motor 404M with a reduction gear (not shown
in the figures) provided together with the motor 404M. The
reduction gear may be omitted.
[0066] Further, the fourth arm member 15 and the fifth arm member
17 of the wrist 16 are coupled via a joint 175. The joint 175
includes a mechanism for supporting one of the fourth arm member 15
and the fifth arm member 17 of the wrist 16, which are coupled to
each other, to be turnable with respect to the other. Consequently,
the fifth arm member 17 of the wrist 16 is configured to be
turnable with respect to the fourth arm member 15 about a fifth
turning axis O5 parallel to the horizontal direction (a y-axis
direction). The fifth turning axis O5 is orthogonal to the fourth
turning axis O4. The turning about the fifth turning axis O5 is
performed according to driving by the fifth driving source 405. The
fifth driving source 405 is driven by the motor 405M and a cable
(not shown in the figures). The motor 405M is controlled by the
robot control device 20 via a motor driver 305 electrically
connected to the motor 405M (see FIG. 3). Note that the fifth
driving source 405 may be configured to transmit a driving force
from the motor 405M with a reduction gear (not shown in the
figures) provided together with the motor 405M. The reduction gear
may be omitted.
[0067] The fifth arm member 17 of the wrist 16 and the sixth arm
member 18 are coupled via a joint 176. The joint 176 includes a
mechanism for supporting one of the fifth arm member 17 of the
wrist 16 and the sixth arm member 18, which are coupled to each
other, to be turnable with respect to the other. Consequently, the
sixth arm member 18 of the wrist 16 is configured to be turnable
with respect to the fifth arm member 17 about a sixth turning axis
O6. The sixth turning axis O6 is orthogonal to the fifth turning
axis O5. The turning about the sixth turning axis O6 is performed
according to driving by the sixth driving source 406. The sixth
driving source 406 is driven by a motor 406M and a cable (not shown
in the figures). The motor 406M is controlled by the robot control
device 20 via a motor driver 306 electrically connected to the
motor 406M (see FIG. 3). Note that the sixth driving source 406 may
be configured to transmit a driving force from the motor 406M with
a reduction gear (not shown in the figures) provided together with
the motor 406M. The reduction gear may be omitted. The fifth
turning axis O5 may be parallel to an axis orthogonal to the fourth
turning axis O4. The sixth turning axis O6 may be parallel to an
axis orthogonal to the fifth turning axis O5.
[0068] As shown in FIG. 3, in the motors or the reduction gears of
the respective driving sources 401 to 406, a first position sensor
(a first angle sensor) 411, a second position sensor (a second
angle sensor) 412, a third position sensor (a third angle sensor)
413, a fourth position sensor (a fourth angle sensor) 414, a fifth
position sensor (a fifth angle sensor) 415, and a sixth position
sensor (a sixth angle sensor) 416 are provided. The position
sensors are not respectively particularly limited. For example, an
encoder, a rotary encoder, a resolver, and a potentiometer can be
used. The position sensors 411 to 416 respectively detect rotation
angles of shaft sections of the motors or the reduction gears of
the driving sources 401 to 406. The motors of the driving sources
401 to 406 are not respectively particularly limited. Examples of
the motors include servomotors such as an AC servo motor and a DC
servo motor and a piezoelectric motor including a piezoelectric
element.
[0069] As shown in FIG. 2, the robot main body 10 includes a force
sensor 81 provided at the distal end section of the arm member 18
of the wrist 16 of the robot arm 5 (between the arm member 18 of
the wrist 16 and the hand 91).
[0070] The force sensor 81 detects a force such as reaction and a
moment received via an insertion object 41 gripped by the hand 91.
The force sensor 81 is not particularly limited. Various force
sensors can be used. Examples of the force sensors include a
six-axis force sensor that detects forces in the axial direction of
three axes (an X axis, a Y axis, and a Z axis) orthogonal to one
another and moments around the axes. Note that, in the following
explanation, the force and the moment are collectively referred to
as force as well. A detection result of the force sensor 81, that
is, a signal output from the force sensor 81 is input to the robot
control device 20.
[0071] An example of initialization of the force sensor 81 is
explained. For the explanation, a circuit configuration of a part
of the force sensor 81 is explained.
[0072] As shown in FIG. 4, the force sensor 81 includes a
piezoelectric element 82 that outputs charges (a signal) according
to a received external force and a conversion circuit 86 that
converts the charges output from the piezoelectric element 82 into
a voltage. The conversion circuit 86 includes an operational
amplifier 83, a capacitor 84, and a switching element 85. An
inverted input terminal (a minus input) of the operational
amplifier 83 is connected to the piezoelectric element 82. A
non-inverted input terminal (a plus input) of the operational
amplifier 83 is earthed to the ground (a reference potential
point). An output terminal of the operational amplifier 83 is
connected to a circuit at a later stage. The capacitor 84 is
connected between an inverted input terminal and the output
terminal of the operational amplifier 83. The switching element 85
is connected between the inverted input terminal and the output
terminal of the operational amplifier 83 and connected in parallel
to the capacitor 84. The switching element 85 is connected to a
driving circuit (not shown in the figure). The switching element 85
executes a switching operation according to ON and OFF signals
received from a driving circuit (not shown in the figure).
[0073] When the switching element 85 is off, the charges output
from the piezoelectric element 82 are accumulated in the capacitor
84 and output to a circuit at a later stage as a voltage.
Consequently, force detection can be performed. Subsequently, when
the switching element 85 is turned on, both terminals of the
capacitor 84 are short-circuited. As a result, the charges
accumulated in the capacitor 84 are discharged and decrease to 0
coulomb. The voltage output to the circuit at the later stage
decreases to 0 volt. Turning on the switching element 85 is
referred to as resetting the conversion circuit 86. In this
example, this is initialization (zero-point correction) of the
force sensor 81. Note that a voltage output from an ideal
conversion circuit 86 is proportional to an amount of charges
output from the piezoelectric element 82. The switching element 85
is not particularly limited. For example, a semiconductor switching
element such as a MOSFET (Metal Oxide Semiconductor Field Effect
Transistor) can be used. Note that the switching element 85 is not
limited to the semiconductor switching element. For example, a
mechanical switch may be used. It goes without saying that the
configuration of the force sensor 81 is not limited to the
configuration explained above.
[0074] As shown in FIG. 3, the robot main body 10 is electrically
connected to the robot control device 20. That is, the driving
sources 401 to 406, the position sensors 411 to 416, and the force
sensor 81 are electrically connected to the robot control device
20.
[0075] The robot control device 20 can cause the arm members 12 to
15 and the wrist 16 to operate independently from one another. That
is, the robot control device 20 can control the driving sources 401
to 406 independently from one another via the motor drivers 301 to
306. In this case, the robot control device 20 performs detection
with the position sensors 411 to 416 and the force sensor 81 and
controls the driving of the driving sources 401 to 406, for
example, angular velocities, rotation angles, and the like
respectively on the basis of detection results of the sensors. In
this case, the robot control device 20 performs predetermined
control such as impedance control (force control) and position
control. A control program for the control is stored in advance in
a recording medium incorporated in the robot control device 20.
[0076] Note that, as shown in FIG. 1, when the robot 1 is a
vertical multi-joint robot, the base 11 is a portion located in the
lowermost part of the vertical multi-joint robot and fixed to the
floor 101 of a setting space. In the base 11, for example, the
motor 401M and the motor drivers 301 to 306 are housed.
[0077] In the wrist 16, as an end effector, the hand 91 that grips
a precision instrument such as a wristwatch is detachably attached
to the distal end section (an end on the opposite side of the
fourth arm member 15) of the wrist 16 (see FIG. 2). Note that the
hand 91 is not particularly limited. Examples of the hand 91
include a hand including a plurality of finger sections (fingers).
The robot 1 can convey the precision instrument by controlling the
operations of the arm members 12 to 15, the wrist 16, and the like
while gripping the precision instrument with the hand 91.
[0078] The configuration of the robot control device 20 is
explained with reference to FIGS. 1 to 3.
[0079] The robot control device 20 includes a first driving-source
control unit 201 that controls the operation of the first driving
source 401, a second driving-source control unit 202 that controls
the operation of the second driving source 402, a third
driving-source control unit 203 that controls the operation of the
third driving source 403, a fourth driving-source control unit 204
that controls the operation of the fourth driving source 404, a
fifth driving-source control unit 205 that controls the operation
of the fifth driving source 405, and a sixth driving-source control
unit 206 that controls the operation of the sixth driving source
406.
[0080] The robot control device 20 calculates, on the basis of
contents of processing performed by the robot 1, a target position
of the distal end section of the wrist 16, that is, a target
position of the hand 91 attached to the wrist 16 and generates a
track for moving the hand 91 to the target position. The robot
control device 20 measures rotation angle of the driving sources
401 to 406 at each predetermined cycle and outputs values
calculated on the basis of results of the measurement respectively
to the driving-source control units 201 to 206 as position commands
for the driving sources 401 to 406 such that the hand 91 (the wrist
16) moves along the generated track. The robot control device 20
performs detection with the position sensors 411 to 416 and the
force sensor 81 and controls driving of the driving sources 401 to
406 respectively on the basis of results of the detection.
[0081] In performing work using the force sensor 81, the robot 1
performs initialization (zero-point correction) of the force sensor
81 according to the control by the robot control device 20. The
robot 1 performs the initialization while the robot arm 5 is moving
at uniform speed. Unless the robot arm 5 is not stopped,
acceleration is not applied if the robot arm 5 is moved at the
uniform speed. Therefore, it is possible to properly initialize the
force sensor 81. The robot 1 initializes the force sensor 81 while
the robot arm 5 is moving. Therefore, it is possible to reduce a
cycle time in the work performed using the force sensor 81. Note
that the robot control device 20 grasps on the basis of an
operation instruction (a command, etc.) of the robot 1 whether the
robot arm 5 is moving at the uniform speed. In the following
explanation, the initialization of the force sensor 81 is also
simply referred to as "initialization".
[0082] The initialization of the force sensor 81 means setting an
output value (a force detection value) of the force sensor 81 to a
predetermined value (a reference value). In other words, the
initialization of the force sensor 81 means eliminating or
reducing, for example, the influence of the gravity due to
fluctuation in the weight of a workpiece, the posture of the robot
arm 5, and the like and the influence of drift due to a leak
current, thermal expansion, and the like of a circuit. That is, the
initialization of the force sensor 81 means setting a value output
from the force sensor 81 because of, for example, the influence of
the gravity due to fluctuation in the weight of a workpiece, the
posture of the robot arm 5, and the like and the influence of a
drift due to a leak current, thermal expansion, and the like of a
circuit to a predetermined value. As the predetermined value, "0"
is preferable.
[0083] As a specific example, for example, as explained above, the
initialization of the force sensor means turning on (closing) the
switching element 85 of the force sensor 81 and discharging charges
accumulated in the capacitor 84 (see FIG. 4).
[0084] As another specific example, the initialization of the force
sensor 81 means reading an output value of the force sensor 81 in
order to treat an output value of the initialized force sensor 81
as a predetermined value. For example, when the output value of the
initialized force sensor 81 is treated as "0", the read output
value of the force sensor 81 is "a". When an output value of the
force sensor 81 in force detection after that is "b", an actual
force detection value is "b-a". Note that a signal processing
circuit that performs the arithmetic operation (the signal
processing) explained above may be provided separately from the
force sensor 81 or may be included in the force sensor 81.
[0085] The uniform speed not only means that speed does not change
at all but also means that an absolute value of a difference
between a maximum and a minimum of the speed is equal to or smaller
than 2 mm/sec.
[0086] When it is determined whether the robot arm 5 is moving at
the uniform speed, speed of which part of the robot arm 5 is set as
a target of the determination is not particularly limited and is
set as appropriate according to conditions. However, the part is
preferably a part where the force sensor 81 of the robot arm 5 is
provided. That is, it is preferable to determine on the basis of
speed of the part where the force sensor 81 of the robot arm 5 is
provided whether the robot arm 5 is moving at the uniform speed.
Note that, in this embodiment, the force sensor 81 is set between
the sixth arm member 18 of the wrist 16 and the hand 91. Therefore,
speed of the distal end section of the robot arm 5, that is, the
distal end section of the sixth arm member 18 of the wrist 16 is
the target of the determination. That is, it is determined on the
basis of the speed of the distal end section of the robot arm 5
whether the robot arm 5 is moving at the uniform speed.
Consequently, in the initialization, it is possible to suppress
acceleration from being applied to the force sensor 81 because of
movement (displacement) of the robot arm 5. It is possible to
properly initialize the force sensor 81.
[0087] As explained above, the initialization only has to be
performed while the robot arm 5 is moving at the uniform speed.
However, it is preferable that the initialization is performed
while the robot arm 5 is moving at the uniform speed and when the
amplitude of a detection value of the force sensor 81 is smaller
than a predetermined threshold T. When it is determined on the
basis of an operation instruction of the robot 1 that the robot arm
5 is moving at the uniform speed, actually, the robot arm 5 may not
be moving at the uniform speed. Therefore, it is possible to surely
determine that the robot arm 5 is moving at the uniform speed.
[0088] Timing of the initialization is not particularly limited if
the robot arm 5 is moving at the uniform speed. However, it is
preferable that the timing is a point in time while the robot arm 5
is moving at the uniform speed and when the amplitude of the
detection value of the force sensor 81 is smaller than the
threshold T. That is, it is preferable to initialize the force
sensor 81 while the robot arm 5 is moving at the uniform speed and
when the amplitude of the detection value of the force sensor 81 is
smaller than the threshold T. Consequently, it is possible to
properly initialize the force sensor 81. It is possible to further
reduce the cycle time.
[0089] The threshold T is preferably equal to or smaller than 10 N
and more preferably equal to or smaller than 1 N.
[0090] By setting the threshold T to the value, in the
initialization, it is possible to suppress acceleration from being
applied to the force sensor 81 because of the movement
(displacement) of the robot arm 5. It is possible to properly
initialize the force sensor 81.
[0091] It is preferable to fix the postures of the wrist 16 and the
hand 91 until the initialization ends. By fixing the postures of
the wrist 16 and the hand 91, it is possible to more surely move
the wrist 16 and the hand 91 at uniform speed. Consequently, it is
possible to properly initialize the force sensor 81.
[0092] A specific example of the work performed using the force
sensor 81 of the robot 1 and the initialization of the force sensor
81 are explained in detail below with reference to FIGS. 5 to 10.
In the following explanation, a control operation of the robot
control device 20 is also explained.
[0093] The work performed using the force sensor 81 is not
particularly limited. However, in this embodiment, an example is
explained in which, as shown in FIGS. 7 to 10, the insertion object
41, which is a first member (a first assembly target), including a
protrusion (an insertion section) 42 is gripped by the hand 91 and
the insertion object 41 (the protrusion 42) is inserted into a hole
(an opening) 47 of an insertion target 46, which is a second member
(a second assembly target), according to impedance control. In this
work, the insertion target 46 is arranged in a second position. The
robot arm 5 is moved from a first position to the second position
according to the control by the robot control device 20. The
insertion object 41 is inserted into the hole 47 of the insertion
target 46. Thereafter, the robot arm 5 is moved to a third
position. Note that in the above explanation and the following
explanation, "move the robot arm 5 to the first position, the
second position, and the third position" means moving the wrist 16
and the hand 91 to the first position, the second position, and the
third position.
[0094] In this work, first, as shown in FIGS. 6 and 7, the robot
control device 20 moves the robot arm 5 to the first position (step
S101).
[0095] Subsequently, as shown in FIGS. 8 and 9, the robot control
device 20 starts movement of the robot arm 5 to the second position
(step S102). The robot control device 20 starts force detection
with the force sensor 81 (step S103). As explained above, a result
of the force detection by the force sensor 81 is used to determine
whether the amplitude of a detection value of the detection is
smaller than the threshold T.
[0096] As shown in FIG. 5, when the robot arm 5 moves from the
first position to the second position, first, speed of the robot
arm 5 changes to a uniform speed period through an acceleration
period in which the speed increases and a period until the speed
stabilizes (a stabilization standby period). The robot control
device 20 grasps the uniform speed period on the basis of an
operation instruction of the robot 1 as well. As explained above,
in the equal speed period, when the amplitude of the detection
value of the force sensor 81 is smaller than the predetermined
threshold T, the robot control device 20 performs the
initialization of the force sensor 81 (step S104). In the equal
speed period, the robot control device 20 communicates and sets
operation conditions (parameters) (step S105). The robot control
device 20 fixes the postures of the wrist 16 and the hand 19 until
the initialization ends. Note that, in the configuration shown in
the figure, the postures of the wrist 16 and the hand 91 are fixed
until the insertion object 41 is inserted into the hole 47 of the
insertion target 46.
[0097] Subsequently, before the insertion object 41 comes into
contact with the insertion target 46, the robot control device 20
starts impedance control (step S106). According to the impedance
control, it is possible to cause the insertion object 41 to trace
the insertion target 46. It is possible to prevent an excessive
force from being applied to the insertion object 41 at an instance
when the insertion object 41 comes into contact with the insertion
target 46 and in a contact state in which the insertion object 41
is in contact with the insertion target 46. The robot control
device 20 moves the robot arm 5 to the second position and inserts
the insertion object 41 into the hole 47 of the insertion target 46
(step S107) (see FIG. 10).
[0098] Subsequently, as shown in FIG. 10, the robot control device
20 moves the robot arm 5 to the third position (step S108). The
robot control device 20 ends the impedance control (step S109).
[0099] Subsequently, the robot control device 20 determines whether
the insertion object 41 is inserted into the hole 47 of the
insertion target 46 (step S110). When determining that the
insertion object 41 is not inserted into the hole 47, the robot
control device 20 returns to step S101 and executes step S101 and
subsequent steps again. When determining that the insertion object
41 is inserted into the hole 47, the robot control device 20 ends
the work.
[0100] Note that, when the amplitude of the detection value of the
force sensor 81 is not smaller than the threshold T in the uniform
speed period and the insertion object 41 is more likely to come
into contact with the insertion target 46, for example, the robot
control device 20 may once stop the robot arm 5 and perform the
initialization.
[0101] As explained above, the robot 1 performs the initialization
of the force sensor 81 without stopping the robot arm 5. Therefore,
it is possible to reduce the cycle time in the work performed using
the force sensor 81. Consequently, it is possible to improve work
efficiency.
Second Embodiment (a Robot)
[0102] FIG. 11 is a schematic diagram showing a robot according to
a second embodiment of the invention.
[0103] Differences of the second embodiment from the first
embodiment are mainly explained below. Explanation of similarities
is omitted.
[0104] As shown in FIG. 11, a robot 1A in the second embodiment is
a double-arm robot. The robot main body 10 of the robot 1A includes
two robot arms 5 and a body section 110 functioning as a base (a
supporting section) that supports the robot arms 5. For example,
the robot 1A can perform work by gripping the insertion object 41
with one of two hands 91 and gripping the insertion target 46 with
the other.
[0105] With the robot 1A, effects same as the effects in the first
embodiment can be obtained.
[0106] Since the robot 1A is a double-arm robot, the robot 1A can
perform various operations and can perform various kinds of
work.
[0107] Note that the number of robot arms is not limited to two and
may be three or more.
Third Embodiment (a Robot System)
[0108] FIG. 12 is a perspective view showing a robot system
according to a third embodiment of the invention.
[0109] Differences of the third embodiment from the first
embodiment are mainly explained below. Explanation of similarities
is omitted.
[0110] As shown in FIG. 12, a robot system 100 includes a robot 1B
and a robot control device (a control unit) 20, which is separate
from the robot 1B. In the robot 1B, the robot control device 20 is
excluded from the robot 1 in the first embodiment. The robot 1B and
the robot control device 20 are electrically connected by a cable
25.
[0111] Note that the robot 1B and the robot control device 20 may
be configured to perform communication by radio.
[0112] With the robot system 100, effects same as the effects in
the first embodiment can be obtained. Note that this embodiment can
be applied to the second embodiment as well.
[0113] The robot, the robot system, and the robot control device
according to the embodiments of the invention are explained above.
However, the invention is not limited to this. The components of
the sections can be replaced with any components having the same
functions. Any other components may be added to the invention.
[0114] The invention may be an invention obtained by combining any
two or more components (features) of the embodiments.
[0115] In the embodiments, the impedance control is explained as
the example of the control performed using the force sensor.
However, in the invention, the control is not limited to the
impedance control. Other examples of the control include compliance
control.
[0116] In the first and third embodiments, the number of the
turning axes of the robot arms is six. However, in the invention,
the number of the turning axes is not limited to six and may be,
for example, two, three, four, five, or seven or more. That is, in
the first and third embodiments, since the wrist includes two arm
members, the number of the arm members of the robot arm is six.
However, in the invention, the number of the arm members is not
limited to six and may be, for example, two, three, four, five, or
seven or more.
[0117] In the invention, the robot (the robot main body) may be
robots of other forms. Specific examples of the robots include a
leg walking (running) robot including leg sections, a scalar robot,
a handler, and an apparatus exclusive for production.
Fourth Embodiment (a Robot System)
[0118] A robot system according to a fourth embodiment of the
invention is explained in detail with reference to the drawings.
FIG. 13 is a diagram showing a schematic configuration example of
the robot system according to the embodiment of the invention. A
robot system 1000 includes a robot 1100, a robot control device
1061, a communication line 1121, and a communication line 1122.
[0119] The robot 1100 is controlled by the robot control device
1061. The robot 1100 is, for example, as shown in FIG. 13, a robot
of an arm type that performs, for example, gripping of a workpiece.
An arm of the robot 1100 includes, for example, a plurality of
joints 1200, a plurality of links 1210, a hand 1220 (a gripping
section), and a force sensor 1230.
[0120] The joints 1200 couples the links 1210, couples a body
section and the link 1210, couples the hand 1220 and the link 1210
to be turnable (turnable within a predetermined range). In the
example shown in the figure, the robot 1100 is a six-axis arm
including six joints.
[0121] The joints 1200 and the hand 1220 include, for example, an
actuator (not shown in FIG. 13) for causing the joints 1200 and the
hand 1220 to operate. The actuator includes, for example, a servo
motor and an encoder. An encoder value (a coordinate indicating the
present position) output by the encoder is used for feedback
control of the robot 1100 by the robot control device 1061.
[0122] The robot 1100 includes a force sensor 1230 in the hand
1220. For example, when a machining target gripped by the hand 1220
comes into contact another object (a machining tool) or the like,
the force sensor 1230 measures an external force (an acting force)
applied from the machining tool and outputs the external force to
the robot control device 1061 via the communication line 1121. A
sensor value (an output value) output by the force sensor 1230 is
used for impedance control of the robot 1100 by the robot control
device 1061 (explained in detail below).
[0123] Note that the six-axis arm is shown in FIG. 13. However, the
number of axes (the number of joints) may be further increased or
reduced. The number of links may be increased or reduced. The
shapes, the sizes, the arrangement, the structures, and the like of
the various members such as the arm, the hand, the links, and the
joints may be changed as appropriate. The position and the like of
the force sensor 1230 may be also changed as appropriate.
[0124] The robot control device 1061 is a device that controls the
operation of the robot 1100. The robot control device 1061 includes
a control unit 1101, a storing unit 1102, an input unit 1103, and
an output unit 1104.
[0125] The control unit 1101 is configured using, for example, a
CPU (Central Processing Unit) and performs various kinds of
arithmetic processing. The various kinds of arithmetic processing
performed by the control unit 1101 are processing explained below
and the like.
[0126] One kind of processing among the kinds of arithmetic
processing performed by the control unit 1101 is position control
for performing movement of the hand 1220. Note that, as shown in
FIG. 14, positions (X, Y, and Z) of the members of the robot 1100
including the hand 1220 are decided according to the X axis, the Y
axis, and the Z axis with a predetermined position (e.g., the
center of a workpiece placing table 1302 shown in FIG. 14) set as
the origin. Note that, in the position control, postures
(.theta..sub.x, .theta..sub.y, and .theta..sub.z), which are values
indicating the postures of the members, may be further used.
[0127] Note that, concerning the position control, the positions of
the members in a three-dimensional space are set using the
positions (X, Y, and Z) and the motions of the members in the
three-dimensional space are controlled. However, for example, the
position control and posture control may be performed on the basis
of the configuration of a visual servo. That is, by stationarily or
movably setting a camera that photographs a machining target
gripped by the hand 1220 of the robot 1100 and comparing a
photographed image of the camera and a reference image prepared in
advance, the position control and the posture control for the robot
may be performed on the basis of a result of the comparison.
[0128] Another kind of processing of the kinds of arithmetic
processing performed by the control unit 1101 is impedance control.
The impedance control means performing the position control to
equalize a sensor value of the force sensor 1230 with a setting
value (a predetermined value) set in advance. That is, if a
machining target is brought into contact with a machining tool with
a predetermined pressing force, the force sensor 1230 outputs a
sensor value same as the pressing force to the control unit 1101.
Therefore, when the sensor value is equal to or larger than the
predetermined value, position control for moving the machining
target away from the machining tool is performed. On the other
hand, when the sensor value is smaller than the predetermined
value, position control for bringing the machining target close to
the machining tool is performed. According to such impedance
control, it is possible to press the machining target against the
machining tool with the predetermined pressing force. Note that,
when an external force is not detected by the force sensor 1230,
the impedance control is not performed.
[0129] The control unit 1101 performs the position control and the
impedance control and outputs a control signal for causing the
robot 1100 to operate to the robot 1100 via the communication line
1122. The robot 1100 grips the machining target with the hand 1220
and moves the machining target to a predetermined position
according to a control signal input from the control unit 1101. The
robot 1100 can press the machining target against the machining
tool with the predetermined pressing force.
[0130] The storing unit 1102 includes a storage medium that stores
various kinds of information. The storing unit 1102 stores, for
example, information concerning a computer program used by the
control unit 1101 and information concerning parameters (e.g.,
target values such as coordinates of the members) used in various
kinds of processing.
[0131] The input unit 1103 receives an input from the outside. The
input unit 1103 includes a keyboard, a mouse, and the like that
receive an operation input of operation by a user. The input unit
1103 may include, for example, a function for receiving an input
from an external apparatus.
[0132] The output unit 1104 performs an output to the outside. The
output unit 1104 includes, for example, a screen (e.g., a liquid
crystal display) that displays various kinds of information to the
user as images and a speaker that outputs information concerning
sound to the user. The output unit 1104 may include a function for
outputting information to the external apparatus.
[0133] A specific example is explained in which the robot system
1000 including the configuration explained above is applied to a
polishing apparatus that polishes (machines) the surface of a
workpiece (a machining target). FIG. 14 is a diagram for explaining
a specific example of the robot system shown in FIG. 13. In FIG.
14, a workpiece 1301 is a machining target that the hand 1220 of
the robot 1100 grips. The workpiece 1301 is, for example, a SUS304
center-less polished round bar .phi.50 mm. In FIG. 14, nine
workpieces 1301 are placed on the workpiece placing table 1302.
[0134] The workpiece placing table 1302 is configured by, for
example, MC Nylon (registered trademark). In the workpiece placing
table 1302, clearance between workpieces is set to make it possible
to mount ten workpieces. When a control signal, which is an
arithmetic result by the position control, is input from the robot
control device 1061, the robot 1100 shown in FIG. 13 grips, with
the hand 1220, one workpiece 1301 placed on the workpiece placing
table 1302 and brings the workpiece 1301 close to a position (an
initial position) away from a rotating tool 1312 by a predetermined
distance such that the workpiece 1301 is polished by a Leutor (the
rotating tool 1312; a machining tool).
[0135] The rotating tool 1312 includes a rotating shaft 1312a
rotated by an electric motor. For example, a grindstone is attached
to the rotating shaft 1312a as a polishing member 1312b (a
polishing tool). The rotating tool 1312 is sandwiched and fixed by
a fixing member 1311a and a fixing member 1311b. The fixing member
1311a and the fixing member 1311b are configured by an aluminum
alloy A5052 and have a system explained below. The fixing member
1311a and the fixing member 1311b are holding and screwing
stationary dies by V blocks. The fixing member 1311a and the fixing
member 1311b hold the rotating tool 1312 in V-shape grooves.
Slip-stop rubber is stuck to contact sections of the fixing member
1311a and the fixing member 1311b with the rotating tool 1312 to
prevent the rotating tool 1312 from moving.
[0136] When a control signal is input from the robot control device
1061, the robot 1100 shown in FIG. 13 brings the workpiece 1301
gripped by the hand 1220 into contact with the rotating polishing
member 1312b from an initial position (e.g., a position shown in
FIG. 14). Since the workpiece 1301 is brought into contact with the
polishing member 1312b, a sensor value of the force sensor 1230 is
input to the control unit 1101. For example, when the sensor value
is equal to or larger than a threshold set in advance, the control
unit 1101 starts the impedance control. Consequently, the workpiece
1301 comes into contact with the polishing member 1312b with the
predetermined pressing force. The surface of the workpiece 1301 is
polished (machined) with a fixed polishing force. In a state in
which the workpiece 1301 is set in contact with the polishing
member 1312b, by moving the workpiece 1301, it is possible to draw
a character on the surface of the workpiece 1301. If the
predetermined pressing force set to a fixed value in advance is
changed according to characters drawn on the workpiece 1301, it is
possible to represent shading as a degree of polishing and draw the
characters on the surface of the workpiece 1301. Note that, rather
than starting the impedance control when the sensor value is equal
to or larger than the threshold set in advance, it is also possible
to steadily perform the impedance control even when the sensor
value is 0.
[0137] Processing performed when the robot system 1000 is applied
to a polishing apparatus that polishes the surface of a workpiece
is explained. FIG. 15 is a flowchart for explaining processing of
control by the robot control device shown in FIG. 13.
[0138] When the user inputs a signal representing a start of work
to the input unit 1103, the robot control device 1061 outputs a
control signal to the robot 1100 and starts the processing shown in
FIG. 15.
[0139] First, the robot 1100 moves the hand 1220 (the gripping
section) to a workpiece placing table (step S1).
[0140] Subsequently, the robot 1100 grips a workpiece 1310 with the
gripping section (step S2).
[0141] The robot 1100 moves the gripped workpiece 1301 to a
predetermined position (an initial position) near the polishing
member 1312b (step S3).
[0142] The robot 1100 causes the workpiece 1301 to approach the
polishing member of the Leutor from the horizontal direction and
brings the workpiece 1301 close to the polishing member side from
the initial position (step S4).
[0143] The robot control device 1061 determines whether the
workpiece 1301 comes into contact with the polishing member 1312b
(step S5). The control unit 1101 performs this determination
according to whether the sensor value of the force sensor 1230 is
equal to or larger than the threshold set in advance. When the
sensor value is equal to or larger than the threshold set in
advance, the control unit 1101 determines that the workpiece 1301
comes into contact with the polishing member (YES in step S5). The
processing proceeds to step S6. On the other hand, when the sensor
value is smaller than the threshold set in advance, processing
returns to step S4 (No in step S5). The control unit 1101 continues
the processing in step S4 until the condition in step S5 is
satisfied.
[0144] Subsequently, the robot 1100 presses the workpiece 1301
against the polishing member 1312b with the predetermined pressing
force for a predetermined period (step S6). In step S6, the
impedance control is performed and the surface of the workpiece
1301 is polished.
[0145] In a state in which the workpiece 1301 is in contact with
the polishing member 1312b, the robot 1100 moves the workpiece 1301
(step S7). A character is drawn on the surface of the workpiece
1301.
[0146] The robot 1100 moves the workpiece 1301 away from the
polishing member 1312b with a pressing force applied in the
opposite direction (step S8).
[0147] Note that, thereafter, the robot 1100 may perform an
operation for wiping polishing wastes adhering to the workpiece
1301. For example, when the robot 1100 is a single-arm robot, the
robot 1100 places, with the hand 1220, the workpiece 1301 on a work
bench other than the workpiece placing table 1302. The robot 1100
may grip sponge, cloth, or the like with the hand 1220 and apply
the wiping operation to the workpiece 1301. Alternatively, the
robot 1100 may place sponge, cloth, or the like on the work bench
and rub the workpiece 1301 gripped by the hand 1220 against the
placed sponge, cloth, or the like to thereby perform the wiping
operation. When the robot 1100 is a double-arm robot, in a state in
which the workpiece 1301 is gripped by the hand 1220 of one arm,
the robot 1100 may grip sponge or the like with the hand 1220 of
the other arm and perform the wiping operation for the workpiece
1301 gripped by the one hand 1220. During such a wiping operation,
by controlling a force applied to the workpiece 1301 with the force
control by the force sensor 1230, it is possible to remove
polishing wastes from the surface of the workpiece 1301 without
causing scratches and the like on the surface of the workpiece 1301
due to the polishing wastes.
[0148] Subsequently, the robot 1100 moves the polished workpiece
1301 to the workpiece placing table and places the workpiece 1301
on the workpiece placing table (step S9). Note that, when a
plurality of characters are drawn on the workpiece surface, the
processing returns to step S3 and the next character is drawn on
the surface of the workpiece 1301.
[0149] As explained above, with the robot system 1000 according to
this embodiment, the force sensor 1230 is provided in the robot
1100 itself rather than on the machining tool 1312 side.
Consequently, the robot control device 1061 keeps a contact state
with of the workpiece 1301 and the polishing member 1312b of the
rotating tool 1312 according to an output value of the force sensor
1230 on which noise is not superimposed. Therefore, it is possible
to accurately keep a force (a polishing force) applied to the
workpiece 1301 fixed.
[0150] Consequently, in a state in which the workpiece 1301 is set
in contact with the polishing member 1312b, by moving the workpiece
1301, it is possible to accurately draw a character on the surface
of the workpiece 1301. If the predetermined pressing force set to
the fixed value in advance is changed on the workpiece 1301
according to characters, it is possible to represent shading with a
degree of polishing and draw a character on the surface of the
workpiece 1301.
Fifth Embodiment (a Robot System)
[0151] FIG. 16 is a diagram showing a schematic configuration
example of a robot system according to a fifth embodiment. A robot
system 1401 according to this application example includes a robot
control device 1461 and a robot (including the other
components).
[0152] In this embodiment, the robot is a double-arm robot
including two manipulators 1021 and 1022 respectively configuring
arms. The robot is configured integrally with the robot control
device 1461. The operation of the robot is controlled according to
a control signal input from the robot control device 1461. The
robot may output a signal indicating an own state or the like to
the robot control device 1461.
[0153] On the upper surface of a housing section 1011, a body
member 1012, a body member 1013, and a body member 1014 are
attached on the upper side in order. The manipulator 1021
configuring the left arm is attached to the left side of the body
member 1014 at the top. The manipulator 1022 configuring the right
arm is attached to the right side of the body member 1014. A wheel
1041 is attached to the left side of the bottom surface of the
housing section 1011. A wheel 1042 is attached to the right side of
the bottom surface of the housing section 1011.
[0154] Note that the robot according to this embodiment is capable
of rotating and moving the wheel 1041 on the left side and the
wheel 1042 on the right side with an external force manually
applied by a user or automatically with a device.
[0155] The robot control device 1461 is housed in the housing
section 1011.
[0156] The manipulators 1021 and 1022 are respectively types of a
vertical multi-joint robot and function as robot arms. The
respective manipulators 1021 and 1022 include gripping sections
1031 and 1032 at the distal ends of thereof.
[0157] Note that a degree of freedom of the manipulators 1021 and
1022 may be an arbitrary degree of freedom, for example, a
three-axis degree of freedom, a six-axis degree of freedom, a
seven-axis degree of freedom, or other degrees of freedom.
[0158] The respective gripping sections 1031 and 1032 grip objects
to be griped (targets).
[0159] In this embodiment, by causing the manipulators 1021 and
1022 (and the gripping sections 1031 and 1032) to operate, it is
possible to move the targets gripped by the gripping sections 1031
and 1032, that is, change the positions and the postures of the
targets.
[0160] The robot control device 1461 controls the manipulator 1021
(and the gripping section 1031) of the left arm and the manipulator
1022 (and the gripping section 1032) of the right arm. The robot
control device 1461 and the manipulators 1021 and 1022 are
connected to be capable of transmitting control signals and the
like via, for example, a wired or wireless line.
[0161] Note that, for example, the robot control device 1461 may
simultaneously control the manipulator 1021 (and the gripping
section 1031) of the left arm and the manipulator 1022 (and the
griping section 1032) of the right arm in association with each
other or may control the manipulator 1021 (and the gripping section
1031) of the left arm and the manipulator 1022 (and the griping
section 1032) of the right arm separately from each other.
[0162] Note that operations performed in the robot system 1401
according to this embodiment are schematically the same as the
operations performed in the robot system. 1000 according to the
fourth embodiment shown in FIG. 13. Therefore, detailed explanation
of the operations is omitted. For example, the polishing work may
be performed using one of the gripping section 1031 and the
gripping section 1032, may be performed in parallel using both of
the gripping section 1031 and the gripping section 1032, or may be
alternately performed by the right arm and the left arm.
[0163] The robot system 1401 according to this embodiment includes
the griping section 1031 and the gripping section 1032. Therefore,
if the robot system. 1401 is applied to the polishing device
explained with reference to FIGS. 14 and 15, it is possible to more
efficiently perform the work for drawing a character on the
workpiece.
[0164] Note that, with the robot system 1000 and the robot system
1401 according to the embodiments, complicated expensive peripheral
devices are unnecessary. It is possible to easily perform contact
work (searching, tracing, fitting, pressing, and the like of
precision components). Anybody can easily perform automation of
work monitoring, immediate graphical representation of a result, a
visual operation check, and a program change.
[0165] The fourth and fifth embodiments are explained in detail
above with reference to the drawings. However, a specific
configuration is not limited to the embodiments. Design and the
like not departing from the spirit of the invention are also
included in the specific configuration.
[0166] For example, the rotating tool is explained as an example of
the polishing device. However, the polishing device may be a
polishing device that performs polishing through vibration
(including ultrasonic vibration) rather than the polishing
apparatus that performs polishing through rotation. That is, the
polishing tool only has to be a vibrating or rotating object.
[0167] Note that it is also possible to record, in a
computer-readable recording medium, a computer program for
realizing the functions of any components in the devices explained
above (e.g., the robot control device 1061 shown in FIG. 13 and the
robot control device 1461 shown in FIG. 16) and cause a computer
system to read and execute the program. It is assumed that the
"computer system" includes an OS (Operating system) and hardware
such as peripheral devices. The "computer-readable recording
medium" means a portable medium such as a flexible disk, a
magneto-optical disk, a ROM (Read Only Memory), or a CD (Compact
Disk)-ROM or a storage device such as a hard disk incorporated in
the computer system. Further, it is assumed that the
"computer-readable recording medium" includes a recording medium
that retains the computer program for a fixed time like a volatile
memory (RAM: Random Access Memory) inside a computer system, which
functions as a server or a client, when the computer program is
transmitted via a network such as the Internet or a communication
line such as a telephone line.
[0168] The computer program may be transmitted from a computer
system that stores the computer program in a storage device or the
like to another computer system via a transmission medium or by a
transmission wave in the transmission medium. The "transmission
medium" for transmitting the computer program means a medium having
a function for transmitting information like a network (a
communication network) such as the Internet or a communication line
such as a telephone line.
[0169] The computer program may be a computer program for realizing
a part of the functions explained above. Further, the computer
program may be a computer program, a so-called differential file (a
differential program), that can realize the functions in
combination with a computer program already recorded in the
computer system.
* * * * *