Download Bilateral Teleoperation of Multiple Cooperative Robots over Delayed

Bilateral Teleoperation of
Multiple Cooperative Robots over
Delayed Communication Network: Application
Dongjun Lee
Mark W. Spong
Oscar Martinez-Palafox
d-lee@control.csl.uiuc.edu, {mspong,pomartin}@uiuc.edu
Research partially supported by the Office of Naval Research (N00014-02-1-0011 and
N00014-05-1-0186), the National Science Foundation (IIS 02-33314 and CCR 02-09202),
and the College of Engineering at the University of Illinois.
Outline
1. Review of the Proposed Control Framework
2. Simulation Results
3. Semi-Experimental Results
4. Conclusions
Bilateral Teleoperation of Cooperative Multi-Robots
Combine advantages of
- bilateral teleoperation: human intervention in uncertain environments
- multi-robot cooperation: mechanical strength/dexterity & robustness/safety
- applications:
remote construction/maintenance of space/under-water/civil structures
in possibly hazardous environments
Semi-Autonomous Teleoperation
behavior of overall group
(and grasped object)
Locked System
Passive
Coupling:
dropping object!!!
decoupling
internal formation shape
(cooperative grasping)
Shape System
- Passive Decomposition [Lee&Li, CDC03] decomposes slave dynamics into
decoupled shape (formation shape) and locked (overall group motion) systems
- Local grasping control of decoupled shape system: secure/tight grasping
regardless of human command via delayed comm. Channel
- Bilateral teleoperation of locked system: by operating the master robot of
manageably small DOF, human can tele-control the behavior of the grasped
object over the delayed comm. channel while perceiving external forces
System Modelling and Grasping Shape Function
Dynamics of
a single master
(m-DOF)
inertia
Coriolis
velocity control
human force
Dynamics of multiple
slave robots
(n1+n2+…+nN-DOF)
Stack
-up
n-DOF product system
(n=n1+n2+…+nN-dimensional)
Grasping Shape Function: Rn→Rn-m
master’s DOF
desired (constant)
grasping shape
grasping shape function
describes internal group
formation shape
Passive Decomposition and Local Grasping Control
Decomposed Slave Dynamics
Locked system:
passive
decoupling
abstracts overall behavior of
multiple slave robots
and grasped object
Shape system:
locked
system
describes internal group
formation of slave robots
(i.e. cooperative grasping)
shape
system
Local Grasping Control
desired grasping shape
FF cancellation of internal force:
although dynamics is decoupled, other
effects (e.g. object’s inertia) can still perturb
the shape system through internal force FE
Scattering-Based Teleoperation of Locked System
Dynamics of
Master Robot and
Slave Locked System
(both are m-DOF)
control
human/combined
external forces
Locked
System
Shape system
(locally controlled)
Scattering-Based Teleoperation of Locked system:
- humans can tele-control the behavior of the grasped object over delayed comm.
channel while perceiving external forces acting on the object and slaves
- asymptotic position coordination/static force reflection
Outline
1. Review of the Proposed Control Framework
2. Simulation Results
3. Semi-Experimental Results
4. Conclusions
Simulation Settings
3-DOF Master
Three 3-DOF Slave Robots
agent1
deformable
object
(no friction)
Delay 0.5s
Delay 0.5s
(x,y)-translation
yaw rotation
agent2
agent3
- grasping shape function is defined s.t. three slaves form an equilateral triangle
(w/ side length L) whose rotation is specified by the heading of agent 2
- human operator can tele-control the position and rotation of the triangle
by operating 3-DOF master robot (translation and yaw)
- 10% identification errors for inertias of robots (nominal: m=1kg, I=1kgm2)
Simulation: Importance of Decoupling
Without Passive Decoupling Control
With Passive Decoupling Control
- no grasped object (just motion coordination) w/ PD-based grasping control
- without decoupling control, grasping shape (i.e. shape system) is perturbed
by human command and overall group behavior
- slight grasping shape distortion w/ decoupling is due to inertial uncertainty
Simulation: Heavy Object Fixtureless Manipulation
With Feedforward Cancellation
of Internal Force
Without Feedforward Cancellation
of Internal Force
- even if dynamics is decoupled, inertial effect of object (w/ frictionless contact)
perturbs cooperative grasping through the internal force FE
- this perturbation can be cancelled out by feedforward cancellation of the internal
force FE (or also by large enough PD-gains)
Heavy Object Manipulation: Contact/Human Force
good load balance
due to grasping
rigidity
due to grasping
shape
deformation
- human can perceive the total inertias of the grasped object and the slave robots
- human can also perceive sensation of grasping loss
- better load-balancing is achieved w/ FF-cancellation of the internal force FE,
as grasping shape becomes more rigid
Simulation: Force Reflection
Three 3-DOF Slave Robots
human
force
agent1
deformable
object
external force
agent2
agent3
due to object’s
deformation
- external forcing (x-direction) on the grasped object is faithfully reflected to the
human operator (i.e. haptic feedback)
- load balancing among slaves is degraded as the grasped object is deformed
in the rigidly-maintained grasping shape
Outline
1. Review of the Proposed Control Framework
2. Simulation Results
3. Semi-Experimental Results
4. Conclusions
Semi-Experiment Setting
2-DOF Master
Three 2-DOF Slave Robots
agent2
deformable
object
Delay 0.5s
external force
Delay 0.5s
PHANToM Desktop:
constrained on plane
(i.e. (x,y)-translation)
agent1
agent3
- three slave robots: 2-DOF point mass dynamics (only x,y translations)
- Phantom Desktop is used as master with its workspace constrained on (x,y)-plane
- Grasping shape function:
q q 
qE (q1 , q2 , q3 )   1 2  4
 q2  q3 
: specifies rotation and shape of the triangle formed by the three slaves
Semi-Experiment: Deformable Object Manipulation
human perceives
inertias of object/slaves
secure/precise
grasping w/ FF-term
due to object
deformation
- x-directional motion (full-range) w/ fixtureless grasping
- grasping security is preserved regardless of human command
- human can perceive the combined inertia of slaves and grasped object
- increase of some slaves' contact force due to inertia/deformation of object
Semi-Experiment: Obstacle Perception
human perceives
external force
due to object
deformation
Secure/precise
grasping w/ FF-term
- external force (x-direction) on the grasped object center
- force generated by the PI-action in the local impedance controls
- object’s deformation again leads in unbalanced load sharing among slaves
Conclusions
We propose a control framework for bilateral teleoperation of multiple
cooperative robots over delayed master-slave comm. channel:
- passive decomposition: the decoupled shape (cooperative grasping)
and locked (behavior of the grasped object) systems
- local grasping control for the shape system: high precision
cooperative grasping regardless of human command/comm. delays
- scattering-based bilateral teleoperation of the locked system:
human can tele-control behavior of the cooperatively grasped
object by operating a small-DOF of the master robot, while
perceiving combined force on the slaves and the grasped object
over the delayed comm. channel
- enforce energetic passivity: interaction safety and stability
- Semi-experiment and simulation results are presented and
validate efficacy of the proposed control framework
Possible impacts on emerging or traditional applications:
- remote construction/maintenance of space/under-water/civil
structures in hostile/hazardous environments