U.S. patent application number 09/858673 was filed with the patent office on 2001-09-06 for tool actuation and force feedback on robot-assisted microsurgery system.
This patent application is currently assigned to California Institute of Technology, a California nonprofit organization. Invention is credited to Boswell, Curtis D., Das, Hari, Ohm, Tim R., Steele, Robert D..
Application Number | 20010020200 09/858673 |
Document ID | / |
Family ID | 26766785 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010020200 |
Kind Code |
A1 |
Das, Hari ; et al. |
September 6, 2001 |
Tool actuation and force feedback on robot-assisted microsurgery
system
Abstract
An input control device with force sensors is configured to
sense hand movements of a surgeon performing a robot-assisted
microsurgery. The sensed hand movements actuate a mechanically
decoupled robot manipulator. A microsurgical manipulator, attached
to the robot manipulator, is activated to move small objects and
perform microsurgical tasks. A force-feedback element coupled to
the robot manipulator and the input control device provides the
input control device with an amplified sense of touch in the
microsurgical manipulator.
Inventors: |
Das, Hari; (Altadena,
CA) ; Ohm, Tim R.; (Grover Beach, CA) ;
Boswell, Curtis D.; (Pasadena, CA) ; Steele, Robert
D.; (Frazier Park, CA) |
Correspondence
Address: |
FISH & RICHARDSON, PC
4350 LA JOLLA VILLAGE DRIVE
SUITE 500
SAN DIEGO
CA
92122
US
|
Assignee: |
California Institute of Technology,
a California nonprofit organization
|
Family ID: |
26766785 |
Appl. No.: |
09/858673 |
Filed: |
May 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09858673 |
May 15, 2001 |
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09292761 |
Apr 14, 1999 |
|
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6233504 |
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60082013 |
Apr 16, 1998 |
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Current U.S.
Class: |
700/260 ;
700/245; 700/248 |
Current CPC
Class: |
G05B 2219/45123
20130101; A61B 34/30 20160201; B25J 9/1689 20130101; A61B 34/71
20160201; G05B 2219/40193 20130101; G06F 3/011 20130101; A61B 34/37
20160201; G05B 2219/40144 20130101; A61B 34/76 20160201; G06F 3/016
20130101 |
Class at
Publication: |
700/260 ;
700/245; 700/248 |
International
Class: |
G05B 015/00 |
Claims
What is claimed is:
1. A microsurgery system, comprising: a robot manipulator having a
plurality of mechanically decoupled joints, said plurality of
mechanically decoupled joints allowing actuation of a joint without
affecting motion of any other joints; an effector coupled to said
robot manipulator to apply a force to an object; and a force
feedback element adapted to amplify a return force from said
effector.
2. The system of claim 1, further comprising: a master control
system coupled to said robot manipulator, said master control
system allowing an operator to input hand movement, where said hand
movement is converted into amount of force applied at the
effector.
3. The system of claim 1, wherein the return force of said force
feedback element provides an exaggerated sense of feel, such that
said sense of feel allows an operator to feel smaller force
feedback than that without said force feedback element.
4. A method of performing a microsurgery, comprising: converting
operator hand movements into a series of forces to be applied by a
manipulator; determining a series of manipulator movements, said
movements performed by a combination of manipulator joint
movements; actuating the manipulator joint movements; providing an
amplified feedback of a return force felt by said manipulator.
5. The method of claim 4, wherein said actuating includes providing
movement of each joints in a mechanically decoupled orientation
such that a joint movement is made without affecting movement of
any other joints.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/292,761, filed Apr. 14, 1999 and issued as
U.S. Pat. No. 6,233,504 on May 15, 2001, which claims benefit of
the priority of U.S. Provisional Application Serial No. 60/082,013,
filed Apr. 16, 1998 and entitled "A Tool Actuation and Force
Feedback on Robot Assisted Microsurgery System."
ORIGIN OF INVENTION
[0002] The invention described herein was made in performance of
work under a NASA contract, and is subject to the provisions of
Public Law 96-517 (35 U.S.C. 202) in which the Contractor has
elected to retain title.
BACKGROUND
[0003] The present specification generally relates to robotic
devices and particularly to a mechanically decoupled
six-degree-of-freedom tele-operated robot system.
[0004] Robotic devices are commonly used in factory-based
environments to complete tasks such as placing parts, welding,
spray painting, etc. These devices are used for a variety of tasks.
Many of the robotic devices do not have completely
mechanically-decoupled axes with passed actuation for transferring
actuation through one joint in order to actuate another joint,
without affecting the motion of any other joints. Also, the devices
are large and bulky and cannot effectively perform small-scale
tasks, such as microsurgical operations. In addition, these devices
are not tendon-driven systems, and thus, do not have low backlash,
which is desirable for microsurgical operations.
[0005] A decoupled six-degree-of-freedom robot system is disclosed
in U.S. Pat. Nos. 5,710,870 and 5,784,542, issued to Ohm et al. The
robot system has an input device functioning as a master to control
a slave robot with passed actuation capabilities, high dexterity,
six degrees-of-freedom with all six axes being completely
mechanically decoupled, low inertia, low frictional aspect, and
force-feedback capabilities.
[0006] The robot system, disclosed in the above-referenced patents,
is a tendon-driven system without any backlash, and is therefore
capable of precisely positioning surgical instruments for
performing microsurgical operations.
SUMMARY
[0007] The inventors noticed, as a result of several simulated
microsurgical operations, that the integration of a high precision
micromanipulator with a highly sensitive force sensor to the slave
robot can enhance the surgeon=s feel of soft tissues. This allows
effective performance of microsurgical tasks with resolution of the
hand motion less than 10 microns. The force sensor readings are
used to amplify forces with high resolution to an input device on
the master control. The amplified forces allow the surgeon
operating the master control handle to feel the soft tissues with
greater sensitivity and to move the handle with exaggeration and
precision. In addition, the push button switches mounted on the
master control handle provides operator control of system enable
and the micromanipulator.
[0008] In one aspect, the present disclosure involves
robot-assisted tasks for use in microsurgery. An input control
device with force sensors is configured to sense hand movements of
an operator. The sensed hand movements actuate a mechanically
decoupled robot manipulator. A microsurgical manipulator, attached
to the robot manipulator, is activated to move small objects and
perform microsurgical tasks. A force-feedback element coupled to
the robot manipulator and the input control device provides the
input control device with an amplified sense of touch in the
microsurgical manipulator.
[0009] In some embodiments, the input control device has a handle
with activation switches to enable or disable control of the robot
manipulator. The activation switches also allow movement of the
microsurgical manipulator.
[0010] In another aspect, a virtual reality system is disclosed.
The virtual reality system includes a plurality of input control
devices configured to sense operator body movements. Each device
has a plurality of joints that are mechanically decoupled for
transferring force sensed actuation through one joint in order to
actuate another joint, without affecting the motion of any other
joints. The operator body movements are translated into
corresponding movements in a virtual reality environment. A
plurality of force-feedback elements provides the input control
devices with feedback of the senses created in the virtual reality
environment.
[0011] In further aspect, a virtual augmentation system to a
real-environment configuration is disclosed. The system includes a
plurality of input control devices configured to sense operator
body movements. Each device has a plurality of joints that are
mechanically decoupled, where the operator body movements are
translated into corresponding movements in a real environment with
certain limitations placed on the movements by a virtual reality
environment. A plurality of force-feedback elements provides the
input control device with feedback of the senses created in the
virtual reality environment to limit movements in the real
environment.
[0012] In further aspect, a microsurgical training system is
disclosed. The system includes a master input control device
configured to sense operator body movements. The system also
includes at least one force-feedback element coupled to the master
input control device and at least one slave device coupled to the
force-feedback element. The force-feedback element is configured to
receive the operator body movements from the master input control
device. The operator body movements of the master input control
device are replicated in the slave device.
[0013] In one embodiment, a data collection and storage device is
coupled to the master input control device. The data collection and
storage device is used to collect and store the operator body
movements for subsequent replay.
[0014] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other embodiments
and advantages will become apparent from the following description
and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] These and other aspects will be described in reference to
the accompanying drawings wherein:
[0016] FIG. 1 is an overview block diagram of components of the
robot-assisted microsurgery (RAMS) system.
[0017] FIG. 2 is a perspective view of a slave robot arm.
[0018] FIG. 3 is one embodiment of the end effector of the slave
robot arm.
[0019] FIG. 4 is a perspective view of a master control device.
[0020] FIG. 5 is a front view of a master control device
handle.
[0021] FIG. 6 is a block diagram of a master handle switch
interface board.
[0022] FIG. 7 is one embodiment of the RAMS system illustrating the
advantages of compact size and lightweight.
[0023] FIG. 8 illustrates a simulated eye microsurgery procedure
using the RAMS system.
[0024] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0025] Micro-surgeons often use a microscope with 20 to 100 times
magnification to help them visualize their microscopic work area.
The microsurgical operations performed by these surgeons require
manipulation of skin and tissue on the order of about 50 microns. A
microsurgical manipulator, such as micro-forceps, can often scale
down the surgeon's hand motions to less than 10 microns. This
allows the average surgeon to perform at the level of the best
surgeons with high levels of dexterity. In addition, the best
surgeons will be able to perform surgical procedures beyond the
capability of human hand dexterity. The integration of the high
precision microsurgical manipulator with a highly sensitive force
sensor to the slave robot enhances the surgeon's feel of soft
tissues and allows effective performance of microsurgical tasks
with resolution of the hand motion less than 10 microns.
[0026] The force sensor readings are used to amplify forces with
high resolution to an input device on the master control. The
amplified forces allow the surgeon operating the master control
handle to feel the soft tissues with greater sensitivity and to
move the handle with greater exaggeration and precision.
[0027] FIG. 1 shows an overview block diagram of components of the
robot-assisted microsurgery (RAMS) system. The components of the
RAMS system have been categorized into four subsystems. They are
the mechanical subsystem 102, the electronics subsystem 104, the
servo-control and high-level software subsystem 106 and the user
interface subsystem 108.
[0028] The mechanical subsystem 102 includes a master control
system 110 with an input device 112 and a slave robot arm 114 with
associated motors, encoders, gears, cables, pulleys and linkages
that cause the tip 116 of the slave robot to move under computer
control and to measure the surgeon's hand motions precisely. The
subsystem 102 also includes slave and master force sensor
interfaces 126, 128, and a master input device handle switch
interface 150.
[0029] The electronics subsystem 104 ensures that a number of error
conditions are handled gracefully. Components of the electronics
subsystem 104 are a Versa Module EuroCard (VME) chassis 120, an
amplifier chassis 122 and safety electronics 124.
[0030] The VME chassis 120 contains VME processor boards 130 used
for high-level system control. The VME chassis 120 also contains
two sets of Programmable Multi-Axis Controller (PMAC) servo-control
cards 134, power supplies, and two cable interface boards 132.
[0031] The amplifier chassis 122 contains the six slave robot motor
drive amplifiers 140 and three master control device motor drive
amplifiers 142. The amplifier chassis 122 also includes a system
control electronics board 144 and an amplifier power supply
146.
[0032] The safety control electronics 124 includes the control
electronics board and brake relay board. The purpose of the braking
function is to hold the motors in place when they are not under
amplifier control. Programmable logic devices (PLDs) in the safety
control electronics module 124 monitors amplifier power, operator
control buttons and the HALT button, and a watchdog signal from the
high-level software and control processor. Any anomaly triggers
brakes to be set on the slave robot joint and a fault LED to be
lighted. The operator must reset the safety control electronics to
re-activate the system.
[0033] The servo-control and high-level software subsystem 106 is
implemented in hardware and software. The subsystem 106 includes
servo-control boards 134 and the computational processor boards
130. Servo-control software functions include setting-up the
control parameters and running the servo-loop on the servo-control
boards 134 to control the six motors, implementing the
communication between the computation and servo-control boards 134,
initializing the servo-control system and communicating with the
electronics subsystem 104 and the user interface subsystem 108.
[0034] The user interface subsystem 108 interfaces with a user,
controls initialization of the system software and hardware,
implements a number of demonstration modes of robot control and
computes both the forward and inverse kinematics.
[0035] In one embodiment of the subsystem 108, the user specifies
the control modes of the system through a graphic user interface
(GUI) implemented on a computer system, such as a personal computer
(PC) or a workstation. Commands entered into the GUI are
transmitted over an Ethernet connection or by a serial interface
and are received on the real-time software side of the system.
[0036] FIG. 2 shows the slave robot arm 114. The arm 114 is a six
degrees-of-freedom tendon-driven robotic arm designed to be compact
yet exhibit very precise relative positioning capability as well as
maintain a very high work volume. Physically, the arm measures 2.5
cm in diameter and is 25 cm long from its base 200 to the tip 202.
The arm 114 is mounted to a cylindrical base housing 200 that
measures 12 cm in diameter by 18 cm long that contains all of the
drives that actuate the arm.
[0037] The joints of the arm 114 include a torso joint 204, a
shoulder joint 206, an elbow joint 208, and a wrist joint 210. The
torso joint 204 rotates about an axis aligned with the base axis
212 and positioned at the point the arm 114 emerges from its base
200. The shoulder joint 206 rotates about two axes 214 that are in
the same plane and perpendicular to the preceding links. The elbow
joint 206 also rotates about two axes 216 that are in the same
plane and perpendicular to the preceding links. The wrist joint 210
makes three-axes rotations called pitch, yaw and roll
rotations.
[0038] The slave wrist 210 design utilizes a dual universal joint
to give a three degrees-of-freedom, singularity free, mechanically
decoupled joint that operates in a full hemisphere of motion. The
master wrist 210 design uses a universal joint to transmit rotation
motion through the joint while allowing pitch and yaw motions about
the joint resulting in singularity free motion over a smaller range
of motion in three degrees-of-freedom.
[0039] FIG. 3 shows one embodiment of the end effector 220 of the
slave robot. The end effector 220 is force sensor instrumented
micro-forceps 304 actuated by a miniature DC motor 302.
Simultaneous sensing of force interactions at the robot tip 306 and
manipulation with the forceps 304 is possible with the end effector
220. Force interactions measured with the force sensor 300 are
amplified, processed and used to drive the master arm to amplify
the sense of touch at the master handle by an amplifier 308.
[0040] FIG. 4 shows a master control device 110 similar to the
slave robot 114. The device 110 also has six tendon-driven joints.
The master control device 110 is 2.5 cm in diameter and 25 cm long.
The base 400 of the master control device 110 houses
high-resolution optical encoders for position sensing. Since the
smallest incremental movement during microsurgery is about 10
microns, 10 encoder counts is the minimum desirable incremental
movement. As a result, one encoder count corresponds to one-micron
movement at the tip of the end effector 306. High-resolution
encoders are necessary for reducing the amount of gearing necessary
to achieve the required positional resolution while limiting
friction.
[0041] In addition, the base 400 preferably includes three arm
motors and three wrist motors to create the force-feedback
capability on the torso 402, shoulder 404, and elbow 406 axes, and
the three-axis wrist 408, respectively. The wrist 408 is coupled to
a six-axis force sensor 410 that is coupled to a handle 412.
[0042] FIG. 5 shows the master control device handle 412. There are
three push button switches mounted on the handle 412 which provide
operator control of the system and the opening and closing of the
micro-forceps 304 on the slave robot arm 220. The enable switch 500
enables operator control of the system. The open switch 502 and the
close switch 504 control the microsurgical manipulator 304 at the
tip of the end effector 306 by opening and closing the
micro-forceps 304, respectively.
[0043] FIG. 6 shows a block diagram of a master handle switch
interface board 150. One switch 600 is used to inform the system
computer that slave motion should be enabled. The output circuit is
a relay 606 that turns system enable on or off. The other two
switches 602, 604 are used to cause the slave robot manipulator 304
to move in with one switch and out with the other and no motion if
both or neither are activated.
[0044] The switches 600, 602, 604 each have a resistor in series
with its contacts. All switch-resistor pairs are connected in
parallel providing a two-terminal switch sensor circuit connecting
the nodes 610 and 612. The resistors are selected with different
weighting values so that each switch has a different effect on the
total resistance of the switch sensor. The switch sensor circuit is
one element in a two-element voltage divider network. When
different switches and combinations of switches are activated the
voltage divider output changes.
[0045] The voltage divider network output changes are measured by a
7-bit analog-to-digital converter (ADC) 614. The numbers generated
by the ADC output reflect the condition of the switches that are
activated. The ADC numbers are decoded into eight discrete ranges
using a lookup table 616. The states are modified in the decode
logic to eliminate unwanted conditions. For example, both motor
direction activated will cause no motor action.
[0046] The enable output circuit is a single-pole-double-throw
relay 606 whose contacts are wired to an input port on the main
computer. The motor driver output has two bipolar drivers 608 that
can drive the motor in either direction or not at all.
[0047] FIG. 7 shows one embodiment of the RAMS system. The figure
illustrates the advantages of compact size and lightweight. The
entire electronics and servo-control subsystems containing the VME
chassis, the amplifier chassis and the force-control boards are
installed on a movable rack 700. A computer, such as a laptop 702,
can be placed on top of the rack 700. The slave robot 704 and the
master control device 706 can be placed around an operating table
with interface cables connecting them to the rack 700.
[0048] Other advantages of the RAMS system include easy
manipulation of the slave robot arm and manipulator, large work
envelope, decoupled joints, low backlash, and low stiction.
[0049] The slave robot arm and manipulator can be easily maneuvered
using the master input device handle and the push-button switches.
The switch operated indexed motion allows the surgeon to
efficiently control the robot arm and manipulator.
[0050] The RAMS system provides a large work envelope because each
joint of the slave robot arm 114 has a large range of motion. The
torso has 165 degrees of motion while both the shoulder and elbow
have a full 360 degrees of motion. This high range of motion is
attained by the double-jointed scheme. The wrist design has 180
degrees of pitch and yaw with 540 degrees of roll. Such large
motion ranges increases the work volume and reduces the chance of a
joint reaching a limit during operation.
[0051] The mechanically decoupled slave and master arm joints of
the RAMS system simplifies kinematic computations. Furthermore,
mechanically decoupled joints provide partial functionality even
with one joint failure.
[0052] The RAMS system provides low backlash by using dual drive
trains that are pre-loaded relative to one another. Low backlash is
essential for doing fine manipulations. Five of the six
degrees-of-freedom have zero backlash and the sixth, which is a
result of the wrist design, has low backlash.
[0053] The RAMS system also provides low stiction with an
incorporation of precision ball bearings in every rotating location
of the robot. This reduces metal-to-metal sliding and minimizes
stiction. Low stiction is effective in providing small incremental
movements without overshooting or instability.
[0054] FIG. 8 illustrates a simulated eye microsurgery procedure
successfully conducted using the RAMS system. The procedure
demonstrated was the removal of a microscopic 0.015-inch diameter
particle from a simulated eyeball 800.
[0055] The RAMS system was demonstrated in other procedures,
including a dual-arm suturing procedure. Two RAMS systems were
configured as left and right arms to successfully perform a nylon
suture to close a 1.5 mm long puncture in a thin sheet of latex
rubber.
[0056] The RAMS system can be used in many other applications such
as a haptic device in virtual reality (VR) system, synthetic
fixtures or virtual augmentation to the real environment, a
simulator to train for microsurgical procedures, and a data
collection system for measuring the hand motions made by an
operator.
[0057] Although the RAMS system was not developed as a VR system,
components of the RAMS system are applicable in the VR system. In
one application, the master control arm is a unique haptic device
that presents virtual or real force interaction to the user related
to touch perception and feedback. The master control arms' ability
to measure hand motions to less than 10 microns in translation and
to 0.07 degrees in orientation and its pencil grasp make it ideal
as an interface for positioning and feeling of a probe in a virtual
environment.
[0058] In another application, the synthetic fixtures or virtual
augmentation to the real environment is implemented on the RAMS
system to assist the user in performing complex tasks. For example,
in the eye surgery procedure, constraints on the motion of the
slave robot are implemented to allow the surgical instrument
mounted on the slave robot to pivot freely about the entry point in
the eyeball. Activation of this mode causes loss of user control in
two degrees of freedom of the slave robot. The automated control
system prevents motion that moves the instrument against the
eyeball wall.
[0059] In another application, the user interface part of the RAMS
system can be used as a simulator to train for microsurgical
procedures. Expert guidance to a novice surgeon can be implemented
by replicating the expert motions of a master device on a similar
device held by the novice.
[0060] In further application, the RAMS system also can be used as
a data collection system for measuring the hand motions made by an
operator of the system. This data is useful for characterizing the
performance of the user. Much may be learned from analysis and
characterization of the collected data including evaluation of the
potential microsurgical abilities of surgical residents, prediction
of the skill-level of a surgeon at any time or providing some
insight into the nature of highly skilled manual dexterity.
[0061] Although only a few embodiments have been described in
detail above, those of ordinary skill in the art certainly
understand that modifications are possible. For example, as an
alternative to constraining the motion of the slave robot in
microsurgery procedure, forces can be simulated on the master
handle that would guide the user into making safe motions. All such
modifications are intended to be encompassed within the following
claims, in which:
* * * * *