DARPA Robotics Challenge

Day 1

Real Time Finals

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

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. Trials

LIPM Trajectory Optimization X vs, Time Y vs. Time COM Footstep COM X vs. Y meters Trials

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 M. de Lasa, I. Mordatch, and A. Hertzmann, “Feature-Based Locomotion Controllers,” ACM Transactions on Graphics, vol. 29, Stephens Trials

Stuck on the door Finals

Handling modeling error and external forces Finals

Failed manipulation Finals

Fall Predictors Finals

A bad step Finals

Why Dynamics Matters

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

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

Can Atlas Be Human Like? 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,…?

Baby Steps To Human-Like Walking Current