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Bilateral Teleoperation of Multiple Cooperative Robots over Delayed Communication Network: Application. Dongjun Lee Mark W. Spong Oscar Martinez-Palafox [email protected], {mspong,[email protected]

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Bilateral Teleoperation of Multiple Cooperative Robots over

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Bilateral teleoperation of multiple cooperative robots over

Bilateral Teleoperation of

Multiple Cooperative Robots over

Delayed Communication Network: Application

Dongjun Lee

Mark W. Spong

Oscar Martinez-Palafox

[email protected], {mspong,[email protected]

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.


Bilateral teleoperation of multiple cooperative robots over

Outline

1. Review of the Proposed Control Framework

2. Simulation Results

3. Semi-Experimental Results

4. Conclusions


Bilateral teleoperation of multiple cooperative robots over

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


Bilateral teleoperation of multiple cooperative robots over

behavior of overall group

(and grasped object)

Locked System

internal formation shape

(cooperative grasping)

Shape System

Passive

decoupling

Semi-Autonomous Teleoperation

Coupling:

dropping object!!!

- 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


Bilateral teleoperation of multiple cooperative robots over

inertia

Dynamics of multiple

slave robots

(n1+n2+…+nN-DOF)

Stack-up

n-DOF product system

(n=n1+n2+…+nN-dimensional)

master’s DOF

System Modelling and Grasping Shape Function

Dynamics of

a single master

(m-DOF)

velocity

Coriolis

control

human force

Grasping Shape Function: Rn→Rn-m

grasping shape function describes internal group formation shape

desired (constant)

grasping shape


Bilateral teleoperation of multiple cooperative robots over

locked system

shape system

desired grasping shape

Local Grasping Control

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

Passive Decomposition and Local Grasping Control

Decomposed Slave Dynamics

Locked system:

abstracts overall behavior of

multiple slave robots

and grasped object

passive

decoupling

Shape system:

describes internal group

formation of slave robots

(i.e. cooperative grasping)


Bilateral teleoperation of multiple cooperative robots over

Locked

System

Shape system

(locally controlled)

Scattering-Based Teleoperation of Locked System

Dynamics of

Master Robot and Slave Locked System

(both are m-DOF)

human/combined

external forces

control

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


Bilateral teleoperation of multiple cooperative robots over

Outline

1. Review of the Proposed Control Framework

2. Simulation Results

3. Semi-Experimental Results

4. Conclusions


Bilateral teleoperation of multiple cooperative robots over

Three 3-DOF Slave Robots

3-DOF Master

agent1

deformable

object

(no friction)

(x,y)-translation

yaw rotation

agent3

agent2

Simulation Settings

Delay 0.5s

Delay 0.5s

- 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)


Bilateral teleoperation of multiple cooperative robots over

Simulation: Importance of Decoupling

With Passive Decoupling Control

Without 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


Bilateral teleoperation of multiple cooperative robots over

Simulation: Heavy Object Fixtureless Manipulation

Without Feedforward Cancellation

of Internal Force

With 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)


Bilateral teleoperation of multiple cooperative robots over

due to grasping shape deformation

good load balance due to grasping rigidity

Heavy Object Manipulation: Contact/Human Force

- 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


Bilateral teleoperation of multiple cooperative robots over

Simulation: Force Reflection

Three 3-DOF Slave Robots

agent1

deformable

object

agent3

agent2

human

force

external force

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


Bilateral teleoperation of multiple cooperative robots over

Outline

1. Review of the Proposed Control Framework

2. Simulation Results

3. Semi-Experimental Results

4. Conclusions


Bilateral teleoperation of multiple cooperative robots over

2-DOF Master

Three 2-DOF Slave Robots

agent2

deformable

object

PHANToM Desktop:

constrained on plane

(i.e. (x,y)-translation)

agent3

agent1

Semi-Experiment Setting

Delay 0.5s

external force

Delay 0.5s

- 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:

: specifies rotation and shape of the triangle formed by the three slaves


Bilateral teleoperation of multiple cooperative robots over

human perceives

inertias of object/slaves

due to object deformation

secure/precise grasping w/ FF-term

Semi-Experiment: Deformable Object Manipulation

- 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


Bilateral teleoperation of multiple cooperative robots over

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


Bilateral teleoperation of multiple cooperative robots over

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


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