Robust Haptic Teleoperation of a Mobile Manipulation Platform - - PowerPoint PPT Presentation

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Robust Haptic Teleoperation of a Mobile Manipulation Platform - - PowerPoint PPT Presentation

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Robust Haptic Teleoperation of a Mobile Manipulation Platform Jaeheung Park, Oussama Khatib System Setup Stanford AI Lab, Stanford University Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results

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SLIDE 1

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Robust Haptic Teleoperation of a Mobile Manipulation Platform

Jaeheung Park, Oussama Khatib Stanford AI Lab, Stanford University

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

1. System Setup

  • Master Haptic Device: PHANTOM 1.0 SensAble
  • Slave Mobile Manipulator: PUMA560 on XR4000
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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

2. Control of a Mobile Manipulator

Null Space Control Γ0 Ωm ˆ Fc Ωf F ∗

f

F ∗

m

F ∗ JT Γ Robot Force Control Control N T q, fc

Σ

ˆ µ + ˆ p ˆ Λ

Σ Σ

Motion

The equations of motion for the end-effector: Λ(q) ˙ ϑ + µ(q, ˙ q) + p(q) + Fc = F Control: Γ = JTF + N TΓ0 F = ˆ ΛF ∗ + ˆ µ + ˆ p + ˆ Fc where F ∗ = ΩfF ∗

f + ΩmF ∗ m

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

3. Teleoperation

Master Device Virtual Spring Slave Robot Environment A human

  • perator

Kvir Ks

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

3. Teleoperation

Master Device Virtual Spring Slave Robot Environment A human

  • perator

Fd Fd Fc

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SLIDE 6

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

3. Teleoperation

Master Device Virtual Spring Slave Robot Environment A human

  • perator

Fd Fd Fc Apply Fd makes Fc Force Control track Fd

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SLIDE 7

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

3. Teleoperation

Master Device Virtual Spring Slave Robot Environment A human

  • perator

Fd Fd Fc Apply Fd makes Fc Force Control track Fd The human

  • perator

feels Fd. Fc ≈ Fd

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SLIDE 8

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

3. Teleoperation

Master Device Virtual Spring Slave Robot Environment A human

  • perator

Kvir Ks Damping Apply Fd makes Fc Force Control track Fd The human

  • perator

feels Fd. Fc ≈ Fd

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SLIDE 9

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Block Diagram

Human Operator xm xs

  • Kvir

Σ sf sp

  • +

Fd Fh Master Device Slave System

xm, xs Master and slave position sp, sf Scaling for position and force Kvir Virtual spring constant Fd Desired contact force for both master and slave

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

4. Force Control

With the equation of motion for each direction in the operational space coordinate, ˙ ϑf = F ∗

f

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

4. Force Control

With the equation of motion for each direction in the operational space coordinate, ˙ ϑf = F ∗

f

and a spring model ˙ Fc = Ksϑf,

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

4. Force Control

With the equation of motion for each direction in the operational space coordinate, ˙ ϑf = F ∗

f

and a spring model ˙ Fc = Ksϑf, The system transfer function can be derived as G(s) = Kse−sTd s(s + K2). Td system input delay K2 additional damping

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Block Diagram

L1 G(s) rk Σ

  • Lr

Observer Σ ˆ pk ˆ xk Fd Fc F ∗

Fc Contact force at the end-effector Fd Desired contact force F ∗ Command input ˆ xk State estimate ˆ pk Input error estimate rk, L1 Reference input, and a scaling factor Lk Full state feed-back gain G(s) System transfer function from F ∗ to Fc

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

5. Stiffness Estimation

The results of force control without adaptation

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  • 50
  • 40
  • 30
  • 20
  • 10

10 137.2 137.4 137.6 137.8 138 138.2 Force [N] Time [sec] Desired Contact Force Estimated Contact Force Measured Contact force

ˆ Ks = 100N/m Ks changes from free space to 3000N/m.

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  • 20
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5 10 15 20 68 69 70 71 72 73 74 75 Force [N] Time [sec] Desired Contact Force Estimated Contact Force Measured Contact Force

ˆ Ks = 3000N/m Ks changes from free space to 300N/m.

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Adaptation Law Two Ideas from experiments: ˆ Ki

s = ˆ

Kf,i

s,1 + ˆ

Kf,i

s,2.

  • 1. Under/Over-estimated Ks shows Different characteristics among the

desired, measured, and estimated contact force. ˆ Ki

s,1 = ˆ

Ki−1

s,1 + ∆ ˆ

Ki

s,1,

where ∆ ˆ Ki

s,1

= k1|Fm − Fe| σd

  • c, |Fm − Fe|

|Fe| + a1 − b1

  • −k2|Fd − Fe| σd
  • c, |Fd − Fe|

|Fe| + a2 − b2

  • ,

σd(c, x) = 1 1 + e−cx.

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SLIDE 16

System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Adaptation Law Two Ideas from experiments: ˆ Ki

s = ˆ

Kf,i

s,1 + ˆ

Kf,i

s,2.

  • 1. Under/Over-estimated Ks shows Different characteristics among the

desired, measured, and estimated contact force. ˆ Ki

s,1 = ˆ

Ki−1

s,1 + ∆ ˆ

Ki

s,1,

where ∆ ˆ Ki

s,1

= k1|Fm − Fe| σd

  • c, |Fm − Fe|

|Fe| + a1 − b1

  • −k2|Fd − Fe| σd
  • c, |Fd − Fe|

|Fe| + a2 − b2

  • ,

σd(c, x) = 1 1 + e−cx.

  • 2. System stiffness, Ks, increases with the applied contact force.

ˆ Ks,2 = Kmin + k3 σd (c0, |Fm| − F0) .

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

6. Experimental Results

  • Position Scale from Haptic Device to PUMA : 2.0
  • Force Scale from PUMA to Haptic Device : 0.1
  • Time Delay in communication : about 26 ms in one direction
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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Moving base teleoperation: Base Motion

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0.05 0.1 0.15 0.2 110 115 120 125 130 135 Base position in lateral direction[m] Time [sec] Desired Position

Base motion in the lateral direction(i.e. along the table) The amplitude is 20 cm and the period is 12 seconds.

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Moving base teleoperation: force response

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5 110 115 120 125 130 135 Force in vertical direction[N] Time [sec] Desired Contact Force Estimated Contact Force

Desired and Estimated Contact Force

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5 110 115 120 125 130 135 Force in vertical direction[N] Time [sec] Desired Contact Force Measured Contact Force

Desired and Measured Contact Force

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Moving base teleoperation: ˆ Ks and position tracking

500 1000 1500 2000 2500 3000 3500 4000 110 115 120 125 130 135 Estimated Environment Stiffness [N/m] Time [sec]

Estimated Environment Stiffness

0.78 0.8 0.82 0.84 0.86 0.88 0.9 0.92 110 115 120 125 130 135 Position in vertical direction[m] Time [sec] End-Effector Haptics

End-effector Tracking Haptic Device Position

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

Moving base teleoperation: force comparison

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5 10 15 110 115 120 125 130 135 Force in vertical direction[N] Time [sec] Desired Contact Force Applied Haptic Force

Desired Contact Force and Applied Haptic Force to User

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5 10 15 110 115 120 125 130 135 Force in vertical direction[N] Time [sec] Measured Contact Force Applied Haptic Force

Measured Contact Force and Applied Haptic Force to User

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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

7. Conclusion

  • Simple teleoperation scheme using an adaptive force control
  • Robust force control using AOB( i.e. a modified Kalman estimator)
  • Fast On-line stiffness adaptation
  • Decoupled control strategy for a mobile manipulator.
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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

7. Conclusion

  • Simple teleoperation scheme using an adaptive force control
  • Robust force control using AOB( i.e. a modified Kalman estimator)
  • Fast On-line stiffness adaptation
  • Decoupled control strategy for a mobile manipulator.

Future Work

  • More systematic algorithm for stiffness adaptation
  • Better user interface for redundant DOF of a mobile manipulator
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System Setup Control of a Mobile . . . Teleoperation Force Control Stiffness Estimation Experimental Results Conclusion Juliet Setting a Dinner . . .

ISER 2004

8. Juliet Setting a Dinner Table