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Sampling Techniques for Probabilistic Roadmap Planners Roland Geraerts and Mark Overmars IAS-8 March 2004.

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Presentation on theme: "Sampling Techniques for Probabilistic Roadmap Planners Roland Geraerts and Mark Overmars IAS-8 March 2004."— Presentation transcript:

1 Sampling Techniques for Probabilistic Roadmap Planners Roland Geraerts and Mark Overmars IAS-8 March 2004

2 Overview Probabilistic roadmaps Test scenes PRM choices Sampling Variation of running times Conclusions

3 Probabilistic Roadmap Method Construction (G =V,E ) Loop c  a free sample add c to the vertices V N c  a set of nodes for all c’ in N c in increasing distance if c’ and c are not connected in G then if local path between c and c’ exists then add the edge c’c to E Forbidden space Free space Sample c Colliding path c c’ c Local path c’ c c

4 Probabilistic Roadmap Method Construction (G =V,E ) Loop c  a free sample add c to the vertices V N c  a set of nodes for all c’ in N c in increasing distance if c’ and c are not connected in G then if local path between c and c’ exists then add the edge c’c to E Query connect sample s and g to roadmap Dijkstra’s shortest path Forbidden space Free space Sample Start / goal Local path Shortest path

5 Test Scenes Comparison of techniques

6 Experimental Setup Environment Single system SAMPLE Same computer Pentium IV 2.66GHz, 1GB memory Same test scenes Cage, clutter, hole, house, rooms, wrench Preprocessing method but single query Average time (s) over 30 runs

7 PRM choices Collision checking on local path Incremental Binary Rotate-at-s Neighbor selecting Nearest-k Component-k Visibility

8 Collision Checking Incremental Binary Rotate-at- s

9 Collision Checking – Results incrementalbinaryrotate-at-s cage clutter hole house rooms wrench

10 Neighbor Selecting Nearest-k Component-k Component Visibility

11 Neighbor Strategy Nearest-k Nearest k neighbors Component Nearest 1 neighbor in each connected component Component-k Nearest k neighbors in each connected component Visibility Only useful nodes, add node/connection only if: Node cannot be connected to other nodes Node can be connected to 2 (or more) connected components

12 Neighbor Strategy – Results nearest-kcomp.comp.-kvisibility cage clutter hole house rooms wrench

13 Uniform Sampling Random Grid

14 Uniform Sampling Cell Halton (variants)

15 Uniform Sampling – Results halton, seed: randomgrid0randomcell cage clutter hole house rooms wrench

16 Advanced Sampling Gaussian Bridge test

17 Advanced Sampling Obstacle based Nearest contact

18 Advanced Sampling Medial axis

19 Advanced Sampling – Results gaussianbridgeobstacleNCMArnd halton cage clutter hole house rooms wrench

20 Variation of Running Times minavgmaxst dev without restart with restart

21 Conclusions Many claims could not be confirmed Local planner Rotate-at-s is worse than binary collision checking Node adding Component-k seems to work best Visibility sampling didn’t perform as well as expected

22 Conclusions Sampling Small difference between uniform methods Halton didn’t outperform uniform sampling but may be preferred (deterministic) Advanced sampling is only useful in scenes with large open areas and some narrow passages It is not necessarily true that a combination of good techniques is good Reduction of variance is desirable

23 Questions Home page: Mail:


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