1 Legged Locomotion Planning Kang Zhao B 659

1 Legged Locomotion Planning Kang Zhao B 659 Intelligent Robotics Spring 2013

Planning Biped Navigation Strategies in Complex Environments • Joel Chestnutt, James Kuffner, Koichi Nishiwaki, Satoshi Kagami 2

O Global terrain map M O Goal O Primitive set {Trans} O Search algorithm 3

Algorithm - Biped Robot Model O 4

Algorithm- State transitions O 1 4 5 2 6 3 0 7 5 A 16 -transitions set

Algorithm- Environment O 6

Algorithm- State Evaluation O Slope angle Location metric to evaluate a location’s cost Roughness Stability Largest bump 7 Safety

Slope angle The slope angle of the surface at the candidate location. Perfectly horizontal surfaces are desired. The slope angle is computed by fitting a plane h(x, y) to the cells in the location. Roughness Stability Largest bump Safety It’s purpose is to take into account the possible inaccuracy of foot positioning. This can be computed using the roughness and largest bump metrics, using 8 the cells around the foot location

Algorithm- State Evaluation Step metric to evaluate cost of taking a step Cost of transition • Penalty for height change • Collision check 9

Algorithm- State Evaluation Heuristic metric to evaluate remaining cost Euclidean distance Relative angle Height difference 10

Best First Search O 11

A* Search O 12

Searching the State Space A schematic view Search tree

Searching the State Space A schematic view Search tree

Searching the State Space A schematic view Search tree

Searching the State Space A schematic view Search tree

Searching the State Space A schematic view Search tree

Searching the State Space A schematic view Search tree

Results O Cluttered terrain 19

Results O Multi-level terrain 20

Results O Uneven ground with obstacles 21

Comparisons O Distance to goal O Transitions and obstacle effects O Metric weights 22

A 40 -transitions set A 26 -transitions set BFS 23

Performance comparison of A* and BFS for increasing numbers of stairs along the path 24

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Local-minimum problem 27

Online Experiments Stereo vision system Walking area map Footstep sequence Planner Trajectory generator 28

Following work O A tired planning Strategy for biped navigation, 2004 O Biped navigation in rough environments using on-board sensing, 2009 29

Multi-Step Motion Planning for Freeclimbing Robots • Tim Bretl, Sanjay Lall, Jean-Claude Latombe, Stephen Rock 30