Lecture 4: Cooperative manipulation - Stanford University · 2019-01-16 · Lecture 4: Cooperative...
Transcript of Lecture 4: Cooperative manipulation - Stanford University · 2019-01-16 · Lecture 4: Cooperative...
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ME 328: Medical Robotics Winter 2019
Lecture 4:Cooperative manipulation
Allison OkamuraStanford University
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What’s Next
• Assignment 1 due today at 4 pm
• Assignment 2 will be posted today (see lab introduction handout also)
• Catherine Mohr this Friday
• Sherry Wren Friday next week (at 8:30 am!)
• Lab Tours scheduled for….
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Cooperative Manipulation
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so-called “steady-hand” robots
Mako’s RIO Robotic Arm Interactive Orthopedic System
JHU Eye Surgery Robot
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steady-hand robot behavior
with RCM: http://www.youtube.com/watch?v=qQEJEM7YeXY
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http://www.youtube.com/watch?v=Wun4AJcFZSw
MAKO Surgical Robot (makoplasty)
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Barrett WAM Arm
The WAM and associated technologies arethe basis for the MAKO surgical robot
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Robodoc is a similar system (with much
more history)
http://robodoc.com/patient_about_history.html
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a more “intelligent” surgical system than pure teleoperation
Manual Surgery Robotic Surgery
close integration with information systems
more active user assistance
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admittance controlthe user’s applied force is measured, and the robot is
controlled to move proportionally to that force
a typical implementation is:
xd = kaf
desired robot position, velocity
ka admittance gain
f force applied by the user (measured)
fa = kp(xd � x) + kd(xd � x)
xd, xd fa actuator force
robot position, velocityx, x
kp, kd proportional and derivative gains
note: not all cooperative manipulators use admittance control, but many do...
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questions
• what happens when is zero?
• how would you create a virtual surface/wall using admittance control?
ka
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admittance controlenables very slow, steady motions
is a an excellent underlying control structure for applying “virtual fixtures” to guide motions
can be applied to teleoperators as well as cooperative manipulators
for cooperative manipulation, it is best used on a very accurate,
non-backdrivable robot
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impedance admittance
F (s) = Z(s)X(s) X(s) = Y (s)F (s)
dual concepts, just different causality
with implications for practicalimplementation on robots
V(t)ZOHProgrammedAdmittance
F(t)
(b)
TServo
Dynamics
V(t)
ZOHProgrammedImpedance
F(t)
(a)
T
!+
_Device
Dynamics
F (t)a
dt!
Figure 1.2: Robots of the (a) impedance and (b) admittance types. F (t) is theexternally-applied force, and V (t) is the resulting robot velocity. For the impedance-type robot, Fa(t) is the actuator force.
1.2 illustrates typical devices of the impedance and admittance types. With either
type of device, the instantaneous power flow from the human to the system is given
by F (t) · V (t).
Both impedance-type and admittance-type devices have desirable characteristics.
Because of the backdrivability of impedance-type devices, they tend to interact
well with a variety of environments, and they allow the stable haptic display of
environments with very low impedance. They can also often be overpowered by a
human in the event of failure, providing a degree of safety. Admittance-type devices
have the desirable characteristics associated with traditional industrial robots –
accuracy, strength, and good disturbance rejection. Admittance-type haptic devices
are also able to stably generate virtual environments with very low admittance (high
impedance).
7
V(t)ZOHProgrammedAdmittance
F(t)
(b)
TServo
Dynamics
V(t)
ZOHProgrammedImpedance
F(t)
(a)
T
!+
_Device
Dynamics
F (t)a
dt!
Figure 1.2: Robots of the (a) impedance and (b) admittance types. F (t) is theexternally-applied force, and V (t) is the resulting robot velocity. For the impedance-type robot, Fa(t) is the actuator force.
1.2 illustrates typical devices of the impedance and admittance types. With either
type of device, the instantaneous power flow from the human to the system is given
by F (t) · V (t).
Both impedance-type and admittance-type devices have desirable characteristics.
Because of the backdrivability of impedance-type devices, they tend to interact
well with a variety of environments, and they allow the stable haptic display of
environments with very low impedance. They can also often be overpowered by a
human in the event of failure, providing a degree of safety. Admittance-type devices
have the desirable characteristics associated with traditional industrial robots –
accuracy, strength, and good disturbance rejection. Admittance-type haptic devices
are also able to stably generate virtual environments with very low admittance (high
impedance).
7
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questions
• what are some advantages and disadvantages of cooperative manipulation as compared to teleoperation?
• what are some advantages and disadvantages of admittance control as compared to impedance control?
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Assignment 2Problem 0: Commentary on seminar
Problem 1: Read/skim papers, answer questions
Problem 2: Implement teleoperators andreview performance data
Problem 3: Implement admittance control andreview performance data
Due Wednesday Jan. 23 at 4 pm
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Lab Introduction
• proper handling of the Phantom Omni robot/haptic devices
• use of the programs you need to test the Omni setup
• opening, modifying, and compiling the template program for writing and testing Omni control laws
• the details of the template program you’ll be working with
• how to interpret the experimental data you save