U.S. patent application number 14/176323 was filed with the patent office on 2014-08-07 for maneuvering system having inner force sense presenting function.
This patent application is currently assigned to TOKYO INSTITUTE OF TECHNOLOGY. The applicant listed for this patent is TOKYO INSTITUTE OF TECHNOLOGY. Invention is credited to Kenji KAWASHIMA, Kotaro TADANO.
Application Number | 20140222204 14/176323 |
Document ID | / |
Family ID | 39738172 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140222204 |
Kind Code |
A1 |
KAWASHIMA; Kenji ; et
al. |
August 7, 2014 |
MANEUVERING SYSTEM HAVING INNER FORCE SENSE PRESENTING FUNCTION
Abstract
A compact, lightweight manipulation system that excels in
operability and has a force feedback capability is provided. When
automatic operation of a slave manipulator 105 that follows manual
operation of a master manipulator 101 is bilaterally controlled by
means of communication, the force acting on the slave manipulator
is fed back to the master manipulator by operating the master
manipulator primarily under electrically-driven speed control and
the slave manipulator primarily under pneumatically-driven force
control. Therefore, in the master manipulator, it is not necessary
to compensate for the dynamics and the self-weight of the master
manipulator in the motion range of a user, allowing highly
accurate, broadband positional control, which is specific to an
electrically-driven system, and in the slave manipulator,
nonlinearity characteristics specific to a pneumatically-driven
system presents passive softness, provides a high mass-to-output
ratio, and produces a large force.
Inventors: |
KAWASHIMA; Kenji;
(Yokohama-shi, JP) ; TADANO; Kotaro;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO INSTITUTE OF TECHNOLOGY |
TOKYO |
|
JP |
|
|
Assignee: |
TOKYO INSTITUTE OF
TECHNOLOGY
TOKYO
JP
|
Family ID: |
39738172 |
Appl. No.: |
14/176323 |
Filed: |
February 10, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12529515 |
Dec 14, 2009 |
8700213 |
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PCT/JP2008/053614 |
Feb 29, 2008 |
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14176323 |
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Current U.S.
Class: |
700/258 |
Current CPC
Class: |
A61B 2090/064 20160201;
A61B 2090/506 20160201; B25J 13/02 20130101; A61B 34/76 20160201;
A61B 34/70 20160201; A61B 34/37 20160201; A61B 2034/305 20160201;
Y10T 74/20305 20150115; B25J 17/0266 20130101; A61B 2017/2929
20130101; B25J 3/04 20130101; A61B 2034/304 20160201; A61B 34/30
20160201 |
Class at
Publication: |
700/258 |
International
Class: |
A61B 19/00 20060101
A61B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2007 |
JP |
2007-051390 |
Claims
1-8. (canceled)
9. A manipulation system having a force feedback capability in
which automatic operation of a slave manipulator that follows
manual operation of a master manipulator is bilaterally
controllable by means of communication, the manipulation system
characterized in that the force acting on the slave manipulator is
fed back to the master manipulator by operating the master
manipulator under electrically-driven speed control and the slave
manipulator under pneumatically-driven force control, wherein the
slave manipulator is driven by the pneumatic actuators, and wherein
the force acting on the slave manipulator is estimated from the
drive forces of the pneumatic actuators by making use of the back
drivability of the pneumatic actuators.
10. The manipulation system having a force feedback capability
according to claim 9, characterized in that the master manipulator
includes a 3-DOF translation unit and a 4-DOF orientation unit
connected to the translation unit, and the slave manipulator
includes a 3-DOF holding unit and a 4-DOF grip unit held by the
holding unit.
11. The manipulation system having a force feedback capability
according to claim 10, characterized in that the translation unit
is a delta mechanism, the orientation unit is a gimbal mechanism,
the holding unit is a combination of a parallel link mechanism and
a gimbal mechanism, and the grip unit is a wire mechanism.
12. The manipulation system having a force feedback capability
according to claim 11, characterized in that the grip unit includes
pneumatic rotary actuators and wires connected to the pneumatic
actuators, and the grip unit is driven by pulling motions of the
wires in response to the motions of the pneumatic actuators.
13. The manipulation system having a force feedback capability
according to claim 12, characterized in that the force acting on
the grip unit is estimated from the drive forces of the pneumatic
actuators by making use of the back drivability of the pneumatic
actuators.
14. The manipulation system having a force feedback capability
according to claim 9, characterized in that compliance-based
control is applied to the slave manipulator.
15. The manipulation system having a force feedback capability
according to claim 9, characterized in that position-based
impedance control in which a force control loop includes a motion
control loop is applied to the master manipulator, and force-based
impedance control in which a motion control loop includes a force
control loop is applied to the slave manipulator.
16. The manipulation system having a force feedback capability
according to claim 9, characterized in that automatic operation of
the slave manipulator that follows manual operation of the master
manipulator is bilaterally controlled by means of wired
communication.
17. The manipulation system having a force feedback capability
according to claim 9, characterized in that the slave manipulator
is controlled by means of (1) and (2): (1) The force fdr that the
tip of the slave manipulator should produce is calculated as
follows: fdr=Kd(xs-xm)+Bd dxs/dt wherein, Kd: the set stiffness of
the slave manipulator xs: the position and orientation of the tip
of the slave manipulator xm: the position and orientation of the
tip of the master manipulator Bd: the set viscosity of the slave
manipulator (2) The target value .tau.drref of the drive torque of
the pneumatically-driven system is calculated as follows:
.tau.drref=-Js(transposition)fdr+Z(qs,dqs/dt,d.sup.2qs/dt.sup.2)
wherein, Js: the Jacobi matrix representing the transition from the
displacements of the joints to the displacement of the tip position
of the slave manipulator Z: the inverse dynamics function for the
slave manipulator qs: the displacement of each joint of the slave
manipulator dqs/dt, d.sup.2qs/dt.sup.2: the speed and acceleration
are determined from a target value of the trajectory of the master
manipulator.
18. The manipulation system having a force feedback capability
according to claim 17, characterized in that the master manipulator
is controlled as follows: dxm/dt is calculated as follows:
dxm/dt=(fm-fs)/Cd wherein, fm: the force that the operator applies
to the tip of the master manipulator fs: fs is determined from the
force fdr that the tip of the slave manipulator should produce Cd:
the set viscosity of the master manipulator.
19. The manipulation system having a force feedback capability
according to claim 9, characterized in that the slave manipulator
is controlled as follows: The target value .tau.drref of the drive
torque of the pneumatically-driven system is calculated as follows:
.tau.drref=-Js(transposition)fdr+Z(qs,dqs/dt,d.sup.2qs/dt.sup.2)
wherein, Js: the Jacobi matrix representing the transition from the
displacements of the joints to the displacement of the tip position
of the slave manipulator fdr: the force that the tip of the slave
manipulator should produce Z: the inverse dynamics function for the
slave manipulator qs: the displacement of each joint of the slave
manipulator dqs/dt, d.sup.2qs/dt.sup.2: the speed and acceleration
are determined from a target value of the trajectory of the master
manipulator.
20. The manipulation system having a force feedback capability
according to claim 9, characterized in that the slave manipulator
is controlled as follows: The target value of the drive torque of
the pneumatically-driven system is calculated by using an equation
comprising an inverse dynamics function of [Z(qs, dqs/dt,
d.sup.2qs/dt.sup.2)]: wherein, qs: the displacement of each joint
of the slave manipulator dqs/dt, d.sup.2qs/dt.sup.2: the speed and
acceleration are determined from a target value of the trajectory
of the master manipulator.
21. The manipulation system having a force feedback capability
according to claim 9, characterized in that the slave manipulator
is controlled as follows: The target value of the drive torque of
the pneumatically-driven system is calculated by using an equation
comprising dqs/dt and d.sup.2qs/dt.sup.2: wherein, qs: the
displacement of each joint of the slave manipulator dqs/dt,
d.sup.2qs/dt.sup.2: the speed and acceleration are determined from
a target value of the trajectory of the master manipulator.
Description
TECHNICAL FIELD
[0001] The present invention relates to a manipulation system in
which automatic operation of a slave manipulator that follows
manual operation of a master manipulator is bilaterally
controllable by means of communication, and particularly to a
manipulation system having a force feedback capability.
BACKGROUND ART
[0002] In recent years, surgical operations have been widely
practiced in the form of endoscopic surgery to improve QOL (Quality
of Life), such as reduction in patient's pain, hospitalization
period, and size of the scar associated with the surgery.
Endoscopic surgery is performed in such a way that an operator
inserts forceps or other related tools through a thin tube (trocar)
and performs the surgery while observing images from a laparoscope.
Since the scar is smaller than that in open surgery, the burden on
the patient is smaller. However, since the operator moves the
forceps or other related tools using the abdominal wall as a
pivotal point, sufficient degrees of freedom are not provided at
the tip of the forceps and hence it is not easy to freely approach
the site to be treated. Such a situation requires a highly skilled
operator. To reduce the burden on the operator, studies on
multi-DOF forceps system have been actively underway, in which
robotics technology is used to impart multiple degrees of freedom
to the tip of forceps.
[0003] The master-slave concept used in commercially available
multi-DOF forceps systems has advantages of, for example,
capability of remotely and intuitively operating the forceps. To
provide more accurate, safer workability, it is desirable to
provide force feedback to the operator. To this end, studies on
forceps with a force sensor provided in the vicinity of the tip of
the forceps are underway. However, such a multi-DOF forceps system
using electric actuators to drive the master and slave portions not
only cannot feed a minute force back to the operator because of a
high reduction ratio, but also has an insufficient movable range
and results in a bulky apparatus. Further, attaching a force sensor
to the forceps is not an easy task in consideration of practical
factors, such as reduction in size, sterilization, and
calibration.
[0004] To address the above problems, studies on a multi-DOF
forceps system are underway, in which pneumatic actuators are used
to drive the master and slave portions. A pneumatic actuator, which
has nonlinear characteristics, is inferior to an electric actuator
in terms of controllability, but has advantages of, for example,
presenting passive softness, having a high mass-to-output ratio,
and producing a large force without a reduction gear train. For
example, a multi-DOF forceps system has been proposed (see the
non-patent document 1), in which the slave portion includes a 3-DOF
forceps manipulator using pneumatic cylinders and the pressure in
each of the pneumatic cylinders is used to estimate the external
force acting on the tip of the forceps instead of using a force
sensor. Further, a multi-DOF forceps system has been proposed (see
the non-patent document 2), which includes a 3-DOF pneumatic
manipulator that holds and drives the 3-DOF forceps manipulator
described in the non-patent document 1 in a region outside the
abdomen.
[0005] Non-patent document 1: Bilateral control of multi-DOF
forceps system having force sensing capability using pneumatic
servo technology, Japan Society of Computer Aided Surgery, pp.
25-31, (2005), Kotaro Tadano, Kenji Kawashima Non-patent document
2: Development of master-slave system having force feedback
capability using pneumatically-driven multi-DOF forceps:
Development of manipulator for holding forceps, Conference on
Robotics and Mechatronics, 1A1-A03, (2006), Kotaro Tadano, Kenji
Kawashima
DISCLOSURE OF THE INVENTION
[0006] In the multi-DOF forceps system described in the non-patent
document 1, the forceps manipulator has only three degrees of
freedom, which does not allow the motion of the human hand to be
reproduced. In the multi-DOF forceps systems described in the
non-patent documents 1 and 2, the forceps manipulator includes a
mechanism that converts the linear motion of a pneumatic cylinder
into rotational motion, so that reduction in weight of the forceps
manipulator is difficult to achieve. Further, the master and the
slave portions are configured in the same manner, which does not
necessarily provide an optimum structure in terms of
operability.
[0007] The invention has been made in view of the above problems.
An object of the invention is to provide a compact, lightweight
manipulation system that excels in operability and has a force
feedback capability.
[0008] To achieve the above object, the manipulation system having
a force feedback capability according to the invention is a
manipulation system in which automatic operation of a slave
manipulator that follows manual operation of a master manipulator
is bilaterally controllable by means of communication. The
manipulation system is characterized in that the force acting on
the slave manipulator is fed back to the master manipulator by
operating the master manipulator primarily under
electrically-driven speed control and the slave manipulator
primarily under pneumatically-driven force control. Therefore, in
the master manipulator, it is not necessary to compensate for the
dynamics and the self-weight of the master manipulator in the
motion range of a user, allowing highly accurate, broadband
positional control, which is specific to an electrically-driven
system, and in the slave manipulator, nonlinearity characteristics
specific to a pneumatically-driven system presents passive
softness, provides a high mass-to-output ratio, and produces a
large force.
[0009] The manipulation system is characterized in that the master
manipulator includes a 3-DOF translation unit and a 4-DOF
orientation unit connected to the translation unit, and the slave
manipulator includes a 3-DOF holding unit and a 4-DOF grip unit
held by the holding unit. Such a configuration allows the motion of
the human hand on the master manipulator side to be reproduced on
the slave manipulator side. Further, the manipulation system is
characterized in that the translation unit, the orientation unit,
the holding unit, and the grip unit are configured as a delta
mechanism, a gimbal mechanism, a combination of a parallel link
mechanism and a gimbal mechanism, and a wire mechanism,
respectively. The master manipulator and the slave manipulator are
thus configured differently from each other, so that the shapes
thereof can be optimized in terms of operability. Further, the
manipulation system is characterized in that the grip unit includes
pneumatic rotary actuators and wires connected to the pneumatic
actuators, and the grip unit is driven by pulling motions of the
wires in response to the motions of the pneumatic actuators. The
grip unit can therefore directly transmit the swing motions of the
pneumatic actuators, so that the weight of the slave manipulator
can be reduced.
[0010] The manipulation system is characterized in that the force
acting on the grip unit is estimated from the drive forces of the
pneumatic actuators by making use of the back drivability thereof.
No force sensor is therefore required on the grip unit, thereby
providing advantages of reducing the size of the grip unit, making
disinfection of the grip unit easy, and eliminating the need for
calibration of the grip unit. The manipulation system is
characterized in that compliance-based control is applied to the
slave manipulator. Therefore, the slave manipulator will not
produce an excessive force. Further, the manipulation system is
characterized in that position-based impedance control in which a
force control loop includes a motion control loop is applied to the
master manipulator, and force-based impedance control in which a
motion control loop includes a force control loop is applied to the
slave manipulator. Therefore, the slave manipulator can be stably
operated by imparting a moderate viscosity effect to the master
manipulator. Further, the manipulation system is characterized in
that automatic operation of the slave manipulator that follows
manual operation of the master manipulator is bilaterally
controlled by means of wired communication. The master manipulator
can therefore remotely operate the slave manipulator by means of
the Internet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic configuration diagram showing a
manipulation system having a force feedback capability according to
an embodiment of the invention;
[0012] FIG. 2 is a perspective view showing the exterior of the
master manipulator shown in FIG. 1;
[0013] FIG. 3 is a perspective view showing the translation unit
shown in FIG. 2;
[0014] FIG. 4 is a perspective view showing the orientation unit
shown in FIG. 2;
[0015] FIG. 5 is a perspective view showing the exterior of the
slave manipulator shown in FIG. 1;
[0016] FIG. 6 is a perspective view showing the holding unit shown
in FIG. 5 and also shows a pneumatic circuit for driving a
pneumatic cylinder;
[0017] FIG. 7 is a perspective view showing the grip unit shown in
FIG. 5;
[0018] FIG. 8 is a perspective view showing the forceps showing in
FIG. 7;
[0019] FIG. 9 is, a perspective view showing the forceps holding
unit shown in FIG. 7; and
[0020] FIG. 10 is a control block diagram of the multi-DOF forceps
system.
DESCRIPTION OF REFERENCE NUMERALS AND SYMBOLS
[0021] 31 computer [0022] 32 servo amplifier [0023] 71 computer
[0024] 72 servo valve [0025] 73 air supplier [0026] 74 pressure
gauge [0027] 100 multi-DOF forceps system [0028] 101 master
manipulator [0029] 103 master controller [0030] 105 slave
manipulator [0031] 107 slave controller [0032] 110 translation unit
[0033] 112 motor [0034] 113 link [0035] 114 parallel link [0036]
120 orientation unit [0037] 122 first motor [0038] 124 second motor
[0039] 126 third motor [0040] 129 force sensor [0041] 132
manipulator finger [0042] 150 holding unit [0043] 153 parallel link
[0044] 155, 156, 157 pneumatic cylinder [0045] 160 grip unit [0046]
170 forceps [0047] 171 forceps shaft [0048] 172 forceps finger
holder [0049] 173, 174 forceps finger [0050] 180 forceps holding
unit [0051] 182, 183, 184, 185 pneumatic rotary actuator [0052]
186, 187, 188, 189 rotary encoder and pressure sensor [0053] 191,
192 pressure gauge [0054] 193 servo valve [0055] 194 regulator
[0056] 195 air supplier
BEST MODE FOR CARRYING OUT THE INVENTION
[0057] An embodiment of the invention will be described with
reference to the drawings. The embodiment, which will be described
below, does not limit the inventive aspects according to the
claims, and of all the combinations of the features described in
the embodiment are not necessarily essential in providing means for
solving the problems.
[0058] FIG. 1 is a schematic configuration diagram showing a
manipulation system having a force feedback capability according to
an embodiment of the invention. The manipulation system having a
force feedback capability is a multi-DOF forceps system 100
including a master manipulator 101, a master controller 103, a
slave manipulator 105, and a slave controller 107. The multi-DOF
forceps system 100 is a remote manipulation system in which
automatic operation of the slave manipulator 105 that follows
manual operation of the master manipulator 101 is remotely
controllable by means of wired communication between the master
controller 103 and the slave controller 107.
[0059] The master manipulator 101 primarily operates under
electrically-driven positional control using electric actuators,
and includes a 3-DOF translation unit 110 configured as a delta
mechanism and a 4-DOF orientation unit 120 connected to the
translation unit 110 and configured as a gimbal mechanism. On the
other hand, the slave manipulator 105 primarily operates under
pneumatically-driven force control using pneumatic actuators, and
includes a 3-DOF holding unit 150 configured as a combination of a
parallel link mechanism and a gimbal mechanism and a 4-DOF grip
unit 160 held by the holding unit 150.
[0060] Use of an electric actuator, particularly a combination of a
high reduction-ratio gear train and an electric motor, has
advantages over the case where a pneumatic cylinder is used, for
example, in that highly accurate, broadband positional control is
possible, and that applying motion control-based force control
eliminates the need for compensation for the dynamics and the
self-weight of the master manipulator 101 in the motion range of
the operator. On the other hand, a pneumatic actuator, which has
nonlinear characteristics, is inferior to an electric actuator in
terms of controllability, but has advantages, for example,
presenting passive softness, having a high mass-to-output ratio,
and producing a large force without a reduction gear train.
[0061] The master controller 103 includes a computer 31 and a servo
amplifier 32. The slave controller 107 includes a computer 71, a
servo valve 72, an air supplier 73, and a pressure gauge 74. The
computer 31 in the master controller 103 sends a tip position
signal, which is obtained by performing kinetic computation on a
signal SPM from each encoder in the master manipulator 101, to the
computer 71 in the slave controller 107 using UDP/IP communication.
The computer 71 in the slave controller 107 sends a control signal
SCS to the servo valve 72 based on the received position signal.
The servo valve 72 adjusts compressed air CPA from the air supplier
73 based on the received control signal SCS, and supplies the
adjusted compressed air to the slave manipulator 105, so that the
operation of the slave manipulator 105 is automatically controlled
to follow the manual operation of the master manipulator 101.
[0062] On the other hand, the computer 71 in the slave controller
107 sends a calculated target value of the force produced at the
tip to the computer 31 in the master controller 103 using UDP/IP
communication. The computer 31 in the master controller 103 sends a
control signal SCM to the servo amplifier 32 based on the received
force signal. Based on the received control signal SCM, the servo
amplifier 32 feeds the force acting on the slave manipulator 105
back to the master manipulator 101.
[0063] FIG. 2 is a perspective view showing the exterior of the
master manipulator 101. FIG. 3 is a perspective view showing the
translation unit 110. FIG. 4 is a perspective view showing the
orientation unit 120. In the master manipulator 101, as shown in
FIG. 2, the orientation unit 120 is fixed to the translation unit
110 with screws, which is in turn fixed to, for example, a housing
(not shown) with screws. The master manipulator 101 is similar to
the slave manipulator 105 in that the number of degrees of freedom
is seven, but differs from the slave manipulator 105 in that the
master manipulator 101 uses a parallel link mechanism and has a
compact structure.
[0064] The translation unit 110 includes a circular mounting plate
111, three motors 112, three links 113, three sets of parallel
links 114, and a triangular fixture plate 115 as shown in FIGS. 2
and 3. The mounting plate 111 has a plurality of through holes 111a
drilled in the vicinity of the outer circumferential edge at
uniform angular intervals, and screws 111b are inserted into the
through holes 111a to fix the mounting plate 111, for example, to a
housing. The three motors 112 are disposed on the mounting plate
111 and fixed thereto with screws at uniform angular intervals (120
degrees) along a circumferential line inside the outer
circumferential edge in such a way that each of the motor shafts
112a is oriented along a tangential line of the mounting
circumferential line. Each of the motors 112 is an AC servo motor
with a harmonic gear transmission and an encoder built therein.
[0065] The link 113 is assembled in such a way that one end (rear
end) thereof is fixed to the motor shaft 112a and the other end
(front end) is supported by a bearing 113a in such a way that the
bearing 113a becomes perpendicular to the axis of the link. The
parallel link 114 includes two links 114a and two link shafts 114b,
and adjacent ends of the two links 114a are rotatably supported at
both ends of the two link shaft 114b in such a way that the two
links 114a can be translated with a predetermined distance
maintained therebetween. One of the link shafts 114b fits in the
bearing 113a attached to the tip of the link 113. The fixture plate
115 is fixed in such a way that a bearing 115a disposed at each
apex of the triangle is oriented parallel to the axis of the
beating 113a attached to the link 113. The other link shaft 114b
fits in the bearing 115a fixed to each apex of the fixture plate
115.
[0066] The thus configured translation unit 110 is a delta
mechanism having three degrees of freedom in total, that is, having
the link 113 being rotatable around the motor shaft 112a of the
motor 112 in the direction indicated by the arrow "a" in FIG. 3,
the parallel link 114 being rotatable around the tip of the link
113 in the same direction as the rotational direction "a" of the
link 113 and in the direction perpendicular thereto indicated by
the arrow "b" in FIG. 3, and the fixture plate 115 being rotatable
around the tip of the parallel link 114 in the same direction as
the rotational direction "a" of the link 113. The translation unit
110 is therefore characterized in that it produces a large
translation force and maintains the same orientation independent of
its position.
[0067] The orientation unit 120 includes, as shown in FIGS. 2 and
4, an attachment plate 121 that is L-shaped in the side view, a
first motor 122, a first motor fixture plate 123 that is U-shaped
in the side view, a second motor 124, a second motor fixture plate
125 that is L-shaped in the side view, a third motor 126, a third
motor fixture plate 127 that is L-shaped in the side view, a
cylindrical rotating arm 128, a force sensor 129, a force sensor
fixture plate 130 that is L-shaped in the side view, a rectangular
column-like manipulation finger support arm 131, and a rod-like
manipulation finger 132. The attachment plate 121 has a plurality
of through holes 121a drilled in one end thereof, and screws 121b
are inserted into the through holes 121a to fix the attachment
plate 121 to the fixture plate 115. The first motor fixture plate
123, to which the first motor 122 is fixed with screws, is fixed to
the other end of the attachment plate 121 with screws in such a way
that the motor shaft 122a is oriented parallel to the fixture plate
115.
[0068] One end of the second motor fixture plate 125 is fixed to
the motor shaft 122a of the first motor 122, and the second motor
124 is fixed to the other end of the second motor fixture plate 125
with screws in such a way that the motor shaft 124a is oriented
perpendicular to the motor shaft 122a of the first motor 122. One
end of the third motor fixture plate 127 is fixed to the motor
shaft 124a of the second motor 124, and the third motor 126 is
fixed to the other end of the third motor fixture plate 127 with
screws in such away that the motor shaft 126a is oriented
perpendicular to the motor shaft 122a of the first motor 122 and
the motor shaft 124a of the second motor 124. The rear end of the
rotating arm 128 is connected and fixed to the motor shaft 126a of
the third motor 126 in such a way that the axial direction of the
rotating arm 128 is oriented in the axial direction of the motor
shaft 126a of the third motor 126.
[0069] The force sensor 129 is fixed to the tip of the rotating arm
128 via the force sensor fixture plate 130 in such a way that the
rotating shaft 129a of the force sensor 129 is oriented
perpendicular to the motor shaft 126a of the third motor 126. The
manipulation finger support arm 131 is supported at the tip of the
rotating arm 128 in such a way that the rear end of the
manipulation finger support arm 131 is rotatable around the
rotating shaft 129a of the force sensor 129. The manipulation
finger 132 includes a hollow cylindrical body 132a and a solid
cylindrical slider 132b that is inserted through the body 132a and
slidable in the axial direction. The tip of the body 132a is
rotatably supported at the tip of the manipulation finger support
arm 131 in the same direction as the rotating shaft 129a of the
force sensor 129. The tip of the slider 132b is inserted and
secured in a hole 128a drilled in a substantially central area of
the rotating arm 128. Each of the first motor 122, the second motor
124, and the third motor 126 is an AC servo motor with a harmonic
gear transmission and an encoder built therein. The force sensor
129 is a six-axis force sensor capable of detecting translational
forces in three axial directions perpendicular to one another and
moments around the three axes.
[0070] The thus configured orientation unit 120 is a serial gimbal
mechanism having four degrees of freedom in total, that is, having
the second motor fixture plate 125 being rotatable around the motor
shaft 122a of the first motor 122 in the direction a in FIG. 4, the
third motor fixture plate 127 being rotatable around the motor
shaft 124a of the second motor 124 in the direction .beta. in FIG.
4, the rotating arm 128 being rotatable around the motor shaft 126a
of the third motor 126 in the direction .gamma. in FIG. 4, the
manipulation finger support arm 131 being rotatable around the
rotating shaft 129a of the force sensor 129 in the direction S in
FIG. 4, and the body 132a of the manipulation finger 132 being
slidable in the axial direction (the direction A in FIG. 4) along
the slider 132b when operated by the operator. The orientation unit
120 is therefore characterized by its broad movable range that
covers the motion of the human hand.
[0071] FIG. 5 is a perspective view showing the exterior of the
slave manipulator 105. FIG. 6 is a perspective view showing the
holding unit 150. FIG. 7 is a perspective view showing the grip
unit 160. In the slave manipulator 105, as shown in FIG. 5, the
grip unit 160 is fixed to the holding unit 150 with screws, which
is in turn fixed to, for example, a housing (not shown) with
screws. The slave manipulator 105 is similar to the master
manipulator 101 in that the number of degrees of freedom is seven,
but differs from the master manipulator 101 in that the slave
manipulator 105 uses a combination of two sets of parallel link
mechanisms and a gimbal mechanism as well as a wire mechanism and
has a compact structure.
[0072] As shown in FIGS. 5 and 6, the holding unit 150 includes a
rectangular base plate 151, a parallel link support shaft 152, two
sets of parallel links 153, a grip unit support base 154, three
pneumatic cylinders (pneumatic actuators) 155, 156, and 157, and
three cylinder fixture plates 158a, 158b, and 158c. Two bearings
151a are disposed on and fixed to the base plate 151 with a
predetermined distance therebetween. The two bearings 151a
rotatably support the parallel link support shaft 152. A rod
support 151b, which rotatably supports a block 155ab fixed to the
tip of the rod 155a of the first pneumatic cylinder 155, is also
disposed on and fixed to the base plate 151 between the bearings
151a. The body 155b of the first pneumatic cylinder 155 is
supported by one end of the cylinder fixture plate 158a, which is
L-shaped in the side view, and the other end thereof is fixed to a
substantially central portion of the parallel link support shaft
152.
[0073] One end of each of two links 153a and 153b, which form one
of the parallel links 153, is rotatably supported at the
corresponding end of the parallel link support shaft 152. With the
two links 153a and 153b held parallel to each other, one end of a
link 153c, which is part of the other parallel link 153, is
rotatably supported at the other end of the link 153b, and a
substantially central portion of the link 153c is rotatably
supported at a substantially central portion of the link 153a. One
end of a link 153d, which is part of the other parallel link 153,
is rotatably supported at the other end of the link 153a. With the
two links 153c and 153d held parallel to each other, the other ends
of the links 153c and 153d are rotatably supported by the cylinder
fixture plate 151.
[0074] The body 156b of the second pneumatic cylinder 156 is
supported by one end of the cylinder fixture plate 158b, which is
L-shaped in the side view, and the other end thereof is rotatably
supported at the portion where the links 153b and 153c are
rotatably supported. A block (not shown) fixed to the tip of the
rod 156a of the second pneumatic cylinder 156 is rotatably
supported between the two ends of the link 153a. The body 157b of
the third pneumatic cylinder 157 is supported by one end of the
cylinder fixture plate 158c, which is L-shaped in the side view,
and the grip unit support base 154 is attached to the cylinder
fixture plate 158c in a slidable manner in the direction in which
the rod 157a of the third pneumatic cylinder 157 moves. The tip of
the rod 157a of the third pneumatic cylinder 157 is fixed to a
fixture plate 154a fixed to the upper portion of the grip unit
support base 154. Each of the pneumatic cylinders 155, 156, and 157
is a low-friction single rod double acting cylinder.
[0075] As shown in FIG. 6, both chambers of each of the pneumatic
cylinders 155, 156, and 157 are connected to respective control
ports of a five-port, flow-control servo valve 193 (five ports in
total: one supply port, two control ports, and two exhaust ports).
A control signal is used to adjust the opening of one of the
control ports of the servo valve 193, and hence adjust the flow
from the supply port into one of the chambers of each of the
pneumatic cylinders 155, 156, and 157. At the same time, the air in
the other chamber is released from the other control port through
the corresponding exhaust port to the atmosphere. The pressure
difference between both chambers of each of the pneumatic cylinders
is thus controlled.
[0076] The thus configured holding unit 150 is a combination of a
parallel link mechanism and a gimbal mechanism, the parallel link
mechanism having three degrees of freedom in total, that is, having
the parallel links 153 being rotatable around the parallel link
support shaft 152 in the direction .phi. in FIG. 6 in response to
the motion of the first pneumatic cylinder 155 and being rotatable
in the direction .phi. in FIG. 6 around the portions where the
parallel link support shaft 152 and the links 153a and 153b are
rotatably supported in response to the motion of the second
pneumatic cylinder 156, and the grip unit support base 154 being
slidable in the direction .rho. in FIG. 6 in response to the motion
of the third pneumatic cylinder 157. The holding unit 150 can
therefore be designed in such a way that the trocar, which is set
in the abdomen of the subject during laparoscopic surgery, is a
stationary point. The holding unit is thus characterized in that it
is not necessary to directly support the forceps at the hole into
which the forceps are inserted, so that the holding unit 150 can be
operated with minimal burden on the body at the hole into which the
forceps are inserted, and the position coordinates of the port of
the trocar are not required in the kinetics computation. Further, a
counterweight 159 is used to mechanically compensate part of the
self-weight of the holding unit 150.
[0077] The grip unit 160, which includes forceps 170 and a forceps
holding unit 180 as shown in FIGS. 5 and 7, is now described also
with reference to FIG. 8, a perspective view showing the forceps
170, and FIG. 9, a perspective view showing the forceps holding
unit 180. The forceps 170 includes a rod-like forceps shaft 171, a
forceps finger holder 172, and two forceps fingers 173 and 174. The
rear end of the forceps shaft 171 is rotatably supported by the
forceps holding unit 180. One end of the forceps finger holder 172
is rotatably supported at the tip of the forceps shaft 171 around a
rotating shaft 172a disposed in a direction perpendicular to the
axis of rotation of the forceps shaft 171. One end of each of the
forceps fingers 173 and 174 is rotatably supported at the other end
of the forceps finger holder 172 around rotating shafts 173a and
174a disposed in a direction perpendicular to the axis of rotation
of the forceps shaft 171 and the rotating shaft 172a of the forceps
finger holder 172.
[0078] The forceps holding unit 180 includes a box-like holding
body 181, four pneumatic rotary actuators (pneumatic actuators)
182, 183, 184, and 185, four sets of rotary encoders and pressure
sensors 186, 187, 188, and 189, four drive pulleys 190, 191, 192,
and 193, one driven pulley 194, and three direction conversion
pulleys 195, 196, and 197. The holding body 181 is fixed to the
grip unit support base 154 in the grip unit 150 with screws. The
forceps shaft 171 is inserted through and rotatably supported by a
bearing 181b attached to a side 181a of the holding body 181 in
such a way that the bearing 181b covers a hole provided in the side
181a, and the driven pulley 194 is attached to the rear end of the
forceps shaft 171.
[0079] The first to fourth pneumatic rotary actuators 182, 183,
184, and 185 include cylindrical bodies 182a, 183a, 184a, and 185a.
Each of the bodies includes a swinging piece (not shown) having a
shaft that is located at the center of the body and can swing
within a predetermined angular range, the swinging piece extending
from the swinging shaft to the inner circumferential surface of the
body, and a partition plate (not shown) extending from the swinging
shaft to the inner circumferential surface of the body. By
supplying and exhausting air through two kinds of ports, air
supply/exhaust ports 182b/182c (183b/183c, 184b/184c, 185b/185c)
provided in the circumferential surface of the body 182a (183a,
184a, 185a), to and from the two chambers partitioned by the
swinging piece and the partition plate so as to swing the swinging
plate, a rotating shaft 182d (183d, 184d, 185d) connected to the
swinging shaft is rotated within a predetermined angular range.
[0080] The first to third pneumatic rotary actuators 182, 183, and
184, to which the first to third rotary encoders and pressure
sensors 186, 187, and 188 are connected, are attached in line to a
side 181c, which is disposed perpendicular to the side 181a of the
holding body 181, in such a way that the rotating shafts 182d,
183d, and 184d pass through three holes 181d arranged in line in
the side 181c, and the first to third drive pulleys 190, 191, and
192 are disposed in line and attached to the tips of the rotating
shafts 182d, 183d, and 184d. The first to third direction
conversion pulleys 195, 196, and 197 are disposed inside the side
181c and rotatably supported next to the first to third drive
pulleys 190, 191, and 192, respectively. Three loop wires (not
shown) run from the first to third drive pulleys 190, 191, and 192
via the first to third direction conversion pulleys 195, 196, and
197 to the rotating shaft 172a of the forceps finger holder 172 and
the rotating shafts 173a and 174a of the two forceps fingers 173
and 174, respectively. The three loop wires thus engage the first
to third drive pulleys 190, 191, and 192 as well as the rotating
shaft 172a of the forceps finger holder 172 and the rotating shafts
173a and 174a of the two forceps fingers 173 and 174,
respectively.
[0081] The fourth swing pneumatic actuator 185, to which the fourth
rotary encoder and pressure sensor 189 is connected, is attached to
the side 181a in such a way that the rotating shaft 185d is
oriented parallel to the forceps shaft 171 and passes through a
hole provided in the side 181a of the holding body 181, and the
fourth drive pulley 193 is disposed next to the driven pulley 194
and attached to the tip of the rotating shaft 185d. A loop wire
(not shown) engages the fourth drive pulley 193 and the driven
pulley 194 so that the loop wire runs between the fourth drive
pulley 193 and the driven pulley 194.
[0082] The thus configured grip unit 160 is a 4-DOF wire mechanism
for bending, gripping, and rotating, that is, having the forceps
finger holder 172 being rotatable around the rotating shaft 172a in
the direction in FIG. 8 in response to the motion of the first
pneumatic rotary actuator 182, the two forceps fingers 173 and 174
being rotatable around the rotating shafts 173a and 174a in the
direction .eta. in FIG. 8 in response to the motions of the second
and third pneumatic rotary actuators 183 and 184, and the forceps
shaft 171 being rotatable around the rotating shaft 185d in the
direction A in FIGS. 8 and 9 in response to the motion of the
fourth pneumatic rotary actuator 185. The forceps 170 and the
forceps holding unit 180 are therefore characterized in that they
are separable from each other in consideration of the disinfection
process.
[0083] FIG. 10 is a control block diagram of the multi-DOF forceps
system 100. A 5-port spool servo valve 172 is used to drive the
pneumatic cylinders 155, 156, and 157 and the pneumatic rotary
actuators 182, 183, 184, and 185. It is also possible to apply a
control method in which a disturbance observer uses the drive force
Fdr of each of the pneumatic cylinders 155, 156, and 157 as well as
the pneumatic rotary actuators 182, 183, 184, and 185, all of which
are pneumatic actuators, (the drive force Fdr is calculated using
the pressure difference between the chambers) to estimate an
external force fext acting on the forceps fingers 173 and 174,
which form the tip of the slave manipulator 105. However, the use
of this control method requires an inverse dynamics model of the
whole portion including the pneumatic cylinders 155, 156, and 157,
the pneumatic rotary actuators 182, 183, 184, and 185, and the
forceps fingers 173 and 174. However, since wires are used for
power transmission, the modeling is not easy due to friction of the
wires and interference among the degrees of freedom. To derive such
a model, a neural network is used to learn a given arbitrary drive
pattern.
[0084] In general, the response in a master-slave system will be
ideal when the position and the force of the master manipulator are
the same as those of the slave manipulator. However, even when such
an ideal response is achieved, and hence the operator feels as if
he/she were directly doing operation with his/her own hands, the
performance of the operation totally depends on the operator. To
address such a problem, a bilateral control system is used, in
which impedance control applied to the master manipulator 101
differs from that applied to the slave manipulator 105.
[0085] The slave controller 107 makes use of the softness of the
pneumatic cylinders 155, 156, and 157 and the pneumatic rotary
actuators 182, 183, 184, and 185 to apply a control method in which
compliance is imparted to the slave manipulator 105. That is, since
air can be compressed, the slave manipulator 105 has softness.
Further, such softness is adjustable by adjusting the pressure of
the compressed air.
[0086] The compliance of the slave manipulator 105 can prevent
generation of an excessive force. The softness of the slave
manipulator 105 provides a shock absorbing effect when the slave
manipulator 105 hits an object hard.
[0087] In this case, when the slave manipulator 105 comes into
contact with a highly rigid environment, the deviation of the
position of the master manipulator 101 from that of the slave
manipulator 105 increases due to the compliance. Even when the
position of the master manipulator 101 deviates from that of the
slave manipulator 105, the operator can work normally because the
slave manipulator 105, which is used for surgery, primarily comes
into contact with an organ and the operator works on the organ
while looking at images of the slave manipulator 105 through an
endoscope.
[0088] On the other hand, the master manipulator 101 desirably
operates in a stably manner by imparting a moderate viscous effect.
To this end, the master controller 103 employs a position-based
impedance control method (admittance control method) in which a
force control loop includes a motion control loop in consideration
of the characteristics of the motors 112, the first motor 122, the
second motor 124, and the third motor 126. The slave controller 107
employs a force-based impedance control method in which a motion
control loop includes a force control loop because the pneumatic
cylinders 155, 156, and 157 and the pneumatic rotary actuators 182,
183, 184, and 185 are characterized by high back-drivability and
low stiffness.
[0089] As shown in FIG. 10, the master controller 103 and the slave
controller 107 control the master manipulator 101 and the slave
manipulator 105, respectively, in such a way that the manipulators
have the following impedance characteristics.
[0090] For the slave manipulator 105,
-fs=Kd(xs-xm)+Bd dxs/dt (1)
[0091] For the master manipulator 101,
fm-fs=Cd dxm/dt (2)
In the above equations, xs: the position and orientation of the tip
(forceps fingers 173 and 174) of the slave manipulator 105 xm: the
position and orientation of the tip (manipulation finger 132) of
the master manipulator 101 fs: the force that the tip of the slave
manipulator 105 applies to the outer environment fm: the force that
the operator applies to the tip of the master manipulator 101 Kd:
the set stiffness of the slave manipulator 105 Bd: the set
viscosity of the slave manipulator 105 Cd: the set viscosity of the
master manipulator 101 To achieve the equation (1), impedance
control including a force control loop is applied to the slave
manipulator 105. The equation of motion of the slave manipulator
105 is expressed in the joint coordinate system as follows:
.tau.dr-Js(transposition)fs=Z(qs,dqs/dt,d.sup.2qs/dt.sup.2) (3)
In the above equation, .tau.dr: the drive torque at each joint of
the slave manipulator 105 Z: the inverse dynamics function for the
slave manipulator 105 q: the displacement of each joint of the
slave manipulator 105 Js: the Jacobi matrix representing the
transition from the displacements of the joints to the displacement
of the tip position of the slave manipulator 105
[0092] To achieve the equation (1), the force fdr that the tip of
the slave manipulator 105 should produce and the target value
.tau.drref of the drive torque of each of the pneumatic cylinders
155, 156, and 157 and the pneumatic rotary actuators 182, 183, 184,
and 185 are calculated as follows:
fdr=Kd(xs-xm)+Bd dxs/dt (4) (in the frame 1 in FIG. 10)
.tau.drref=-Js(transposition)fdr+Z(qs,dqs/dt,d.sup.2qs/dt.sup.2)
(5) (in the frame 2 in FIG. 10)
[0093] Assuming that the dynamic characteristics of the pneumatic
cylinders 155, 156, and 157 and the pneumatic rotary actuators 182,
183, 184, and 185 are satisfactory so that .tau.drref coincides
with .tau.dr, the equation (4) is substituted into the equation
(5), which is then substituted into the equation (3) to derive the
equation (1). In practice, to prevent the equation (5) from being
unstable due to phase retardation, the speed and acceleration among
the inputs in the inverse dynamics model are determined from a
target value of the trajectory of the master manipulator 101 (in
the frame 3 in FIG. 10). To produce the torque calculated by using
the equation (5) at each joint, mechanics computation is used to
convert the torque into the drive force target value Fdrref of each
of the pneumatic cylinders 155, 156, and 157 and the pneumatic
rotary actuators 182, 183, 184, and 185.
Fdrref=Ja.tau.drref (6) (in the frame 4 in FIG. 10)
In the above equation, Ja: Jacobian representing the transition
from the displacements of the pneumatic cylinders 155, 156, and 157
and the pneumatic rotary actuators 182, 183, 184, and 185 to the
displacements of the joint
[0094] Then, PI control is carried out to produce the drive force
calculated by using the equation (6).
u=(Kap+Kai/s)(Fdrref-Fdr) (7) (in the frame 5 in FIG. 10)
In the above equation, u: the control voltage for the servo valve
172 Kap: proportional gain Kai: integral gain Fdr: the drive forces
of the pneumatic cylinders 155, 156, and 157 and the pneumatic
rotary actuators 182, 183, 184, and 185 calculated from pressure
values
[0095] Admittance control is applied to the master manipulator 101
to achieve the equation (2).
dxm/dt=(fm-fs)/Cd (8) (in the frame 6 in FIG. 10)
dqm/dt=Jm(inverse)dxm/dt (in the frame 7 in FIG. 10)
As seen from the equation (8), the contact force between the slave
manipulator 105 and the external environment is required. When the
impedance control is applied to the slave manipulator 105, fdr
coincides with fs, so that fdr is supplied as an estimated value to
the master controller 103 and the slave controller 107 (in the
frame 8 in FIG. 10). The target drive force value Fdrref of each of
the pneumatic cylinders 155, 156, and 157 and the pneumatic rotary
actuators 182, 183, 184, and 185 can be produced in a quick and
precise manner by the differential pressure control loop in each of
the cylinders and actuators. It is therefore possible to compensate
the characteristics disadvantageously affecting the positioning,
such as air compression properties and a deviation of the neutral
point of the valve.
[0096] As described above, according to the multi-DOF forceps
system 100 of this embodiment, the force acting on the slave
manipulator 105 is fed back to the master manipulator 101 by
operating the master manipulator 101 primarily under
electrically-driven speed control and the slave manipulator 105
primarily under pneumatically-driven force control. Therefore, in
the master manipulator 101, it is not necessary to compensate for
the dynamics and the self-weight of the master manipulator 101 in
the motion range of the operator, allowing highly accurate,
broadband positional control, which is specific to an
electrically-driven system, and in the slave manipulator 105,
nonlinearity characteristics specific to a pneumatically-driven
system presents passive softness, provides a high mass-to-output
ratio, and produces a large force. Further, the slave manipulator
105, which is configured as a pneumatically-driven system, can be
installed in an apparatus involving a magnetic field, for example,
an MRI (Magnetic Resonance Imaging), and used in surgery.
[0097] Since the master manipulator 101 includes the 3-DOF
translation unit 110 and the 4-DOF orientation unit 120 connected
to the translation unit 110, and the slave manipulator 105 includes
the 3-DOF holding unit 150 and the 4-DOF grip unit 160 held by the
holding unit 150, the motion of the human hand on the master
manipulator 101 side can be reproduced on the slave manipulator 105
side. Since the translation unit 110, the orientation unit 120, the
holding unit 150, and the grip unit 160 are configured as the delta
mechanism, the gimbal mechanism, the combination of the parallel
link mechanism and the gimbal mechanism, and the wire mechanism,
respectively, the master manipulator 101 and the slave manipulator
105 are configured differently from each other and the shapes
thereof can be optimized in terms of operability. Since the grip
unit 160 includes pneumatic rotary actuators 182, 183, 184, and 185
and wires connected to the pneumatic rotary actuators 182, 183,
184, and 185, and the grip unit 160 is driven by pulling motions of
the wires in response to the motions of the pneumatic rotary
actuators 182, 183, 184, and 185, the grip unit 160 can directly
transmit the swing motions of the pneumatic rotary actuators 182,
183, 184, and 185. Such a configuration allows reduction in weight
of the slave manipulator 105.
[0098] Further, since the force acting on the grip unit 160 is
estimated from the drive forces of the pneumatic cylinders 155,
156, and 157 and the pneumatic rotary actuators 182, 183, 184, and
185 by making use of the back drivability thereof, no force sensor
is required on the grip unit 160, thereby providing advantages of
reducing the size of the grip unit 160, making disinfection of the
grip unit 160 easy, and eliminating the need for calibration of the
grip unit 160. Moreover, since the compliance-based control is
applied to the slave manipulator 105, the slave manipulator 105
will not produce an excessive force.
[0099] Since the position-based impedance control in which a force
control loop includes a motion control loop is applied to the
master manipulator 101, and the force-based impedance control in
which a motion control loop includes a force control loop is
applied to the slave manipulator 105, the slave manipulator 105 can
be stably operated by imparting a moderate viscosity effect to the
master manipulator 101. That is, the control system according to
this embodiment allows the operator to feel as if he/she pushes and
pulls the master manipulator 101 fixed to a stationary wall via a
damper. It is also possible to connect the master manipulator 101
to the slave manipulator 105 via a spring and a damper. The values
of the spring and the damper are adjustable by selecting the
control parameters.
[0100] In the embodiment described above, although the multi-DOF
forceps system 100 remotely controllable by means of wired
communication has been described, the multi-DOF forceps system 100
may be a system using wireless communication or a system that is
controllable from a nearby location. Further, although the
multi-DOF forceps system 100 has been described as an endoscopic
surgery-assisting apparatus, the multi-DOF forceps system 100 can
be configured as an apparatus for training a doctor or an apparatus
for evaluating skill. Although the invention has been described
with reference to the multi-DOF forceps system 100 used in medical
fields as a manipulation system having a force feedback capability,
the invention is not limited thereto. The invention is generally
applicable to various manufacturing fields.
* * * * *