CS 326 A: Motion Planning Probabilistic Roadmaps Sampling and Connection Strategies

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

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

Multi-Query Strategy

Single-Query Strategy mbmbmbmb mgmgmgmg

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

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

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???