1. Self-Collision Detection and Prevention for Humonoid Robots Paper by James Kuffner et al. Presented by David Camarillo

2. Introduction  Efficient geometric approach to detecting link interference for articulated robots  Fast, feature-based minimum distance determination  Full-body trajectories are checked prior to execution for potentially self-collisions

3. Collision Detection in Robotics  Mobile robots Collision with environmental obstacles or other robots  Articulated robots Self-collision also needs to be checked e.g.) Serial-chain manipulators, Humanoid robots

4. Humanoid Robots  The robot consists of a tree of connected links  Torso is the root with five serial chain branches 2 arms + 2 legs + 1 neck- head chain

5. Number of Pairs to be checked  Assume that joints limits prevents collision between a given link and its parent link

6. H7 Humonoid Robot  A total of 31 links : N=31  Eliminate unnecessary pairs which cannot collide each other Heuristic or exhaustive search approach Full (435 pairs) Pruned (76 pairs)

7. Collision-free Trajectory Generation User Desired Trajectory Collision Detector Online Trajectory Manager Pre-Calculated Walking Patterns Collision-free Trajectory

8. Interference Detection  Trajectory sampling Binary collision results 1) Swept volumes Computations are difficult and expensive 2) Trajectory discretization Preferred due to its simplicity, but collisions may not be detected

9. Interference Detection cont.  Bounds and collision-free guarantees A conservative measure of the minimum distance can guarantee a collision-free motion Maximum joint velocities are bounded

10. Interference Detection cont.  Protective Hulls Convex protective hulls of each link as conservative approximation provide for safety margin, and efficient computation

11. Interference Detection cont.  Minimum Distance Determination Voronoi-clip(V-clip)  No hierarchical bounding volumes  Execution time dependent on model geometry, and velocity, not distance  “Almost constant time” User can add padding to account for errors in modeling and control

12. Self-Collision in Walking

13. Control System for Safe Walking  Could incorporate with balancing scheme  More Practical to detect before hand  Experiments with joystick controlled 3-step trajectory

14. Future Work  Dynamic pruning by considering joint angles during trajectory simulation  Investigating alternative methods which could work with non-convex hulls