Class #7: Sampling and Connection Strategies for Probabilistic Roadmaps
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The Bridge Test strategy (left) is aimed at producing a higher density of milestones in narrow passages. Workspace-based sampling (center) tries to predict narrow passage areas in configuration space from an analysis of the workspace. The small-step retraction strategy (right) slightly dilates free space to increase expansiveness.

• Topics
  - Multi-query vs. single-query sampling
  - Sampling vs. connection strategies
  - Workspace-based strategies
  - Filtering strategies
  - Adaptive strategies
  - Deformation strategies
  - Delayed collision checking
• Readings:
• Filtering strategies:
  - Gaussian sampling:
  V. Boor, M.H. Overmars, A.F. van der Stappen. The Gaussian sampling strategy for probabilistic roadmap planners. Proc. IEEE Int. Conf. on Robotics and Automation, pp. 1018-1023, 1999 [pdf].
  - Bridge test:
  D. Hsu, T. Jiang, J. Reif, and Z. Sun. The Bridge Test for Sampling Narrow Passages with Probabilistic Roadmap Planners. Proc. IEEE Int. Conf. on Robotics and Automation, Taipei, 2003. [pdf]
• Workspace-based strategy:
  H. Kurniawati and D. Hsu. Workspace-Based Connectivity Oracle: An Adaptive Sampling Strategy for PRM Planning. In S. Akella et al., editors, Proc. Int. Workshop on the Algorithmic Foundations of Robotics (WAFR), Springer, 2006. [pdf].
• Small-step retraction:
  M. Saha, J.C. Latombe, Y.-C. Chang, F. Prinz. Finding Narrow Passages with Probabilistic Roadmaps: The Small-Step Retraction Method. Autonomous Robots, 19(3):301-319, Dec. 2005. [pdf]
• Delayed collision-checking:
  G. Sánchez and J.C. Latombe. On Delaying Collision Checking in PRM Planning – Application to Multi-Robot Coordination, Int. J. of Robotics Research, 21(1):5-26, January 2002. [pdf] (skip the section on multi-robot coordination)
• Slides