On Improving the Clearance for Robots in High-Dimensional Configuration Spaces Roland Geraerts and...

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On Improving the Clearance for Robots in High-Dimensional Configuration Spaces

Roland Geraerts and Mark Overmars

IROS 2005

Outline

• Related work

• Retraction algorithm

• Algorithmic details

• Experiments

• Conclusions

Related Work

• Preprocessing techniques– Extract path from graph with cycles– Create path along the medial axis

• Post processing technique– Retract path to the medial axis (MA)

d

d

Related Work

• Preprocessing techniques– Extract path from graph with cycles– Create path along the medial axis

• Post processing technique– Retract path to the medial axis (MA)

Related Work

• Preprocessing techniques– Extract path from graph with cycles– Create path along the medial axis

• Post processing technique– Retract path to the medial axis (MA)

Initial path Retraction to MA Retraction to ridges

Retraction Algorithm

Algorithmic Details – Metric

Algorithmic Details – Vector

Algorithmic Details – Validate

maximumstep size

Experimental Setup

• Pentium 4 (2.66GHz)

• Comparison of retraction techniques– Workspace (1 run)– Configuration space (100 runs)

• Environments / paths

planar (2 dofs) hole (6 dofs) manipulator (6 dofs)

Experimental Results

min avg time

initialworkspaceC-space

0.351.801.79

2.844.494.47

0.01.5

15.0

initial paths workspace C-space

n.a.

Clearance

min avg time

initialworkspaceC-space

0.210.441.27

1.553.374.69

0.01.5

50.0

min avg time

initialworkspaceC-space

0.01 n.a.0.16

0.13 n.a.0.33

0.0 n.a.60.0

Conclusions

• Clearance along paths is improved– No complicated data structures are needed– The algorithm can handle robots with an

arbitrary amount of DOFs

• Running times are too high for online usage– Does not matter for high-cost environments– Smarter implementation decreased the running

times by an order of magnitude

Current Work

• Retraction of a roadmap yields online performance

Reachability roadmap Retracted roadmap

Current Work

• Retraction of a roadmap yields online performance

Reachability roadmap Retracted roadmap