darpa robotics challenge cga/dw. day 1
TRANSCRIPT
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DARPA Robotics Challengewww.cs.cmu.edu/~cga/dw
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Day 1
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Real TimeFinals
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Optimization All The Way Down
• Multi-level optimization:– Footstep Optimization (Discrete + Continuous) – Trajectory Optimization (Continuous)– Optimization-Based Inverse Dynamics: Greedy
continuous optimization (Quadratic Program = QP) for full body at the current instant.
Trials
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Multi-Level Control• Trajectory: External forces at contacts drive
center of mass (COM).
Rotation is more complicated:– Constant angular momentum– Rigid body equivalent– General case
• QP: Redundancies and constraints resolved for full body behavior.
xmF
IIFr )(
0)( Fr
dtIdLFr /)()(
Trials
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LIPM Trajectory Optimization
X vs, Time
Y vs. Time
COM
Footstep
Footstep
Footstep
COM
COM
X vs. Y
meters
Trials
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Optimization-Based “Inverse Dynamics” (QP)
Objectives:• Dynamics• Task Objectives• COM Acceleration• Torque About COM• Reference Pose Tracking• Minimize Controls
Constraints:• Center of Pressure• Friction Cone• Joint Torque Limits
dq
C
bw
bw
bw
bw
q
Aw
Aw
Aw
Aw
NNNN
33
22
11
33
22
11
M. de Lasa, I. Mordatch, and A. Hertzmann, “Feature-Based Locomotion Controllers,” ACM Transactions on Graphics, vol. 29, 2010.
Stephens
Trials
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Stuck on the door
Finals
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Handling modeling error and external forces
Finals
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Finals
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Failed manipulation
Finals
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Fall Predictors
Finals
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A bad stepFinals
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Why Dynamics Matters
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Wheels win?• All wheeled/tracked robots plowed through
debris.• All other robots walked over rough terrain.• KAIST – walked on stairs• Nimbro, RoboSimian – no stairs• Leg/wheel hybrids good if there is a flat
floor somewhere under the pile of debris.• Wheeled/tracked vehicles fell: need to
consider dynamics, need to be able to get up (CHIMP, NimbRo), and get un-stuck.
Finals
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Whole-Body Locomotion
• No robot used railings, walls, door frames, or objects in the environment for physical guidance, stabilization, or support.
• Some robots used arms to get out of the car.
Finals
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Can Atlas Be Human Like?www.cs.cmu.edu/~cga/dw
• Slow (0.5m/s)• Slow (0.6s/step)• Short steps 0.35m
(half human 0.7m)• Flat foot walking• Bent knees• No heel strike or
toe push off• Fixed pelvis
orientation
• Minimal vertical COM acceleration -> GRF
• Minimal horizontal COM acc. -> GRF
• COP fixed at center of foot
• Not robust to external perturbations or modeling error.
• Soft ground, sand,…?
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Baby Steps To Human-Like Walking
Current
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Current
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