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

Clearance Based Path Optimization for Motion Planning

Roland Geraerts and Mark OvermarsICRA 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 path Shortcut Partial shortcut

Path Quality – Clearance Method

Remove redundant nodes Retract path to medial axis Remove branches

Can help improving path length

Query path Retracted path No branches

Path Quality – Clearance

Retract path to medial axis Retract sample to medial axis

d2 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

0

200

400

600

Initial path Redundantnodes

Shortcut MA +Shortcut

Partialshortcut

MA+Partialshortcut

Optimal

Pat

h l

eng

th

translation

rotation400%

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

0

250

500

750

Initial path Redundantnodes

Shortcut MA +Shortcut

Partialshortcut

MA+Partialshortcut

Optimal

Pat

h l

eng

th

translation

rotation

256%

65%24% 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

0

40

80

120

Initial path Redundantnodes

Shortcut MA + Shortcut Partial shortcut MA+Partialshortcut

Optimal

Pat

h le

ng

th

translation

rotation

41% 14% 0%

184%

112%

36%

23%

Future Work

Extension to other robot types

Preprocessing techniques

Questions

Home page: www.cs.uu.nl/~roland

Mail: [email protected]