Clearance Based Path Optimization for Motion Planning Roland Geraerts and Mark Overmars ICRA 2004

Problem setting Low quality paths Often long detours Discontinuity Unnecessary motions Quality criteria Length Clearance Combination

Path Quality – Length Post processing Path pruning Shortcut Partial shortcut

Path Quality – Length Path pruning Fast and simple heuristic Translational dist. improves considerably Rotation is more difficult to remove

Path Quality – Length Shortcut More general than path pruning Simple technique Fast convergence

Path Quality – Length Weakness of the shortcut heuristic Path can still contain many redundant (rotational) motions Creating shortcuts on large portions will fail Partial shortcut Query pathShortcutPartial shortcut

Path Quality – Clearance Method Remove redundant nodes Retract path to medial axis Remove branches Can help improving path length Query pathRetracted pathNo branches

Path Quality – Clearance Retract path to medial axis Retract sample to medial axis d 2 x d 4 x d

Path Quality – Clearance Retract path to medial axis Maximum stepsize s between samples

Path Quality – Clearance Retract path to medial axis Redundant branches redundant branch

Path Quality – Clearance Remove redundant branches Maximum step size

Path Quality – Combination Technique Retract path to medial axis Increase size of robots Create partial shortcuts Result Reasonable short path Path has a particular minimum amount of clearance where it is possible

Experimental Setup – Path Length Environment SAMPLE 3 test scenes/paths Focus Free flying objects Post processing

Experiments – Simple Corridor Simple scene, cylinder Many motions are redundant Redundant motions are easy to remove

Experiments – Simple Corridor Simple scene, cylinder Many motions are redundant Redundant motions are easy to remove 400% 27% 16%14% 1%2%0%

Experiments – Corridor Elbow shaped object is forced to rotate Little clearance to corridors

Experiments – Corridor Elbow shaped object is forced to rotate Little clearance to corridors 256% 65% 24% 11% 5%0%

Experiments – Hole Object must rotate to get through the hole Clearance is small inside the hole

Experiments – Hole Object must rotate to get through the hole Clearance is small inside the hole 41% 14% 0% 184% 112% 36% 23%

Future Work Extension to other robot types Preprocessing techniques

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