1. CS 326 A: Motion Planning http://robotics.stanford.edu/~latombe/cs326/2003 Probabilistic Roadmaps Sampling and Connection Strategies

2. Issues  Where to sample new milestones?  Sampling strategy  Which milestones to connect?  Connection strategy  Goals:  Minimize roadmap size  Achieve good coverage and connectivity

3. Main Distinction  Multi-query roadmaps  Pre-compute roadmap  Re-use roadmap for answering queries  Single-query roadmaps  Compute a roadmap from scratch for each new query

4. Multi-Query Strategy

5. Single-Query Strategy mbmbmbmb mgmgmgmg

6. Multi-Query Strategies Connections to nearest neighbors Acyclical connections Multi-stage sampling Obstacle-sensitive sampling Narrow-passage sampling

7. Single-Query Strategies mbmbmbmb mgmgmgmg Diffusion Adaptive step Lazy collision checking

8. Papers  Paper 1: Gaussian sampling and Bridge test  Multi-query roadmap  Obstacle-sensitive strategies: Place more samples near boundary of obstacle region  Bridge test: more specifically oriented toward finding narrow passage  Paper 2:Visibility-based roadmaps  Multi-query roadmap  Makes explicit use of visibility notion in free space  Reduces the size of final roadmap, but does it reduce cost???