Transcript Bilateral Teleoperation of Multiple Cooperative Robots over Delayed

Bilateral Teleoperation of
Multiple Cooperative Robots over
Delayed Communication Network: Theory
Dongjun Lee
Mark W. Spong
[email protected], [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.
Outline
1. Motivations
2. Problem Formulation
3. Passive Decomposition of Slave Robots
4. Control Design
5. Conclusions
Part II: Simulation and Semi-Experiment
Motivations
Applications:
1. Space Structure Construction/Maintenance
- Hubble telescopes, International Space Station,…
2. Remote Construction/Maintenance of Civil
Structures
Bridge, Highway,
Tall buildings,…
3.-Operations
in Hazardous
Environments
- Nuclear plants, Deep water, …
Bilateral Teleoperation
- Human’s intelligent intervention
in uncertain environments
Multi-Robot Cooperation
- Mechanical strength and dexterity
- Robustness and safety
Bilateral Teleoperation
of Multiple
Cooperative Robots
Challenges and Requirements
1. Abstraction
- human is able to operate only small DOF simultaneously
2. Secure grasping
- no dropping of the grasped object
3. Haptic feedback
- crucial for manipulation tasks
4. Interaction safety and stability
- stably coupled with humans, objects, and environments
Outline
1. Motivations
2. Problem Formulation
3. Passive Decomposition of Slave Robots
4. Control Design
5. Conclusions
Dynamics of Master and Multiple Slave Robots
Dynamics of
a single master
(m-DOF)
Dynamics of multiple
slave robots
(n1+n2+…+nN-DOF)
Stack
-up
n-DOF product system
(n=n1+n2+…+nN-dimensional)
inertia
Coriolis
velocity control human
force
Grasping Shape Function: Holonomic Constraints
master’s DOF
- m-dim. holonomic constraints on the config. space of slave robots (m < n)
- assumed to address the internal formation shape for cooperative grasping
- smooth and full-rank Jacobian (i.e. smooth submersion)
- overall group motion evolving on m-dim. level sets (submanifold)
q q 
qE (q1 , q2 , q3 )   1 2  4
 q2  q3 
q1
m-dim.
level
sets
q2
Grasping shape control objective
desired (constant)
grasping shape
q3
Communication and Control (C&C) Structure
- C&C delay between the master and the slaves
- Centralized C&C module for multiple slaves
- negligible delays among the slaves
- workspaces of slaves are close to each other (e.g. cooperative grasping)
Semi-Autonomous Teleoperation Architecture
Observation:
- secure grasping is of foremost importance for safety
- the system cannot be completely free from time-delay,
i.e. system performance would be compromised in some aspects
Semi-autonomous teleoperation:
1. local grasping control
- secure grasping immune to communication-delay
- autonomous control would be enough due to simplicity of
cooperative grasping control objective
2. delayed bilateral teleoperation
- communication-delay effect confined in bilateral teleoperation
- sluggish response could be taken care of by intelligent humans
- delayed teleoperation is relatively well-studied areas
Energetic Passivity for Safe/Stable Interaction
Energetic
passivity
total slave-ports
mechanical power
master-port
mechanical power
- passive with total master/slave mechanical power as supply rate
- stable interaction with any E-passive humans[Hogan]/objects/environments
Outline
1. Motivations
2. Problem Formulation
3. Passive Decomposition of Slave Robots
4. Control Design
5. Conclusions
Passive Decomposition of Multiple Slaves Robots
behavior of overall group
(and grasped object)
Locked System
Coupling:
dropping object!!!
internal group coordination
(cooperative grasping)
Shape System
The Passive Decomposition [Lee&Li, CDC03] decouples the locked and
shape systems from each other while enforcing passivity
- Can achieve tight/secure grasping regardless of overall group behavior
- Ensure secure grasping and interaction stability simultaneously
Orthogonal Decomposition w.r.t. Inertia Metric
Grasping shape function
Locked system velocity vL :
parallel w.r.t. the level sets of qE:
(behavior of grasped object and total
group)
Shape system velocity vE :
orthogonal complement w.r.t. inertia matrix
(cooperative grasping)
Tangent space
decomposition
basis of
kernel of qE
basis of
orthogonal space
locked system
velocity vL
shape system
velocity vE
Passive Decomposition of Slave Group Dynamics
Original Slave
Dynamics
Passive
Decomposition
Decomposed
Dynamics
- Shape system ((n-m)-DOF) explicitly represents cooperative grasping shape qE(q)
- Locked (m-DOF) system describes overall group behavior
- Locked and shape dynamics are similar to usual mechanical systems:
- ML(q), ME(q) : symmetric and positive-definite
- ML(q)-2CL(q,q), ME(q)-2CE(q,q) : skew-symmetric
- Coupling is energetically conservative: Passive Decoupling
- CLE(q,q) =-CELT(q,q) -> vLTCLE(q,q)qE + qETCELT(q,q)vL=0
- Power and kinetic energy are also decomposed
Energetic Structure of Decomposed Dynamics
Original System
Decomposed System
passive
decoupling
- We can decouple the shape system (cooperative grasping) and the locked
system (overall group) from each other while enforcing passivity
- Desired cooperative grasping and overall group behavior can be achieved
simultaneously while enforcing interaction stability
Outline
1. Motivations
2. Problem Formulation
3. Passive Decomposition of Slave Robots
4. Control Design
5. Conclusions
Semi-Autonomous Control
Decomposed
Dynamics
Scattering-based teleoperation
control for decoupled
locked system
Total Slave
Control
Local grasping control
control for decoupled
shape system
Passive decoupling
Local Grasping Control
Grasping Dynamics
(Decoupled Shape System)
PD/FF-based Control
desired grasping shape internal force
estimate of
internal force
- Adjusting qEd, and PD-gains, fixtureless grasping can be achieved for flexible object
- Although dynamics is decoupled, other effects (e.g. inertia of object) can still perturb
the shape system via the internal force FE: feedforward cancellation is necessary
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
(decoupled)
Shape system
(locally
controlled)
By operating the master robot of manageably small DOF, human operators
can tele-control the behavior of the grasped object over the delayed
master-slave communication channel while perceiving combined external
forces acting on the grasped object and slaves
Scattering-Based Symmetric Teleoperation
Scattering Variables
incident (to comm.)
reflected (from comm.)
(Power Decomposition)
line impedance
(user-specific)
Impedance Control
(PI-Control)
Symmetric Scattering-Based Teleoperation:
- scattering communication (to passify comm. delays) and impedance (PI) controls
- asymptotic position-error convergence proof with Z=Kv
(i.e. matching condition [Stramigioli et al, TRA03])
: so far, only boundedness of position-error has been established.
- force reflection in static manipulation (negligible acceleration/velocity)
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 communication channel
- enforce energetic passivity: interaction safety and stability are enhanced
Part II will present simulation and semi-experiment results.