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Reducing motion of linear track

asked 2017-08-23 16:22:35 -0500

Vlad222 gravatar image

updated 2017-09-06 08:39:10 -0500

Hello all,

Question is about MoveIt! and OMPL. I have 7DOF move_group with 6DOF KUKA and 1DOF slider (linear axis). I plan motion with RRT-Connect and have large translations of slider. For example slider usually moves 1 meter forward and 1 meter back to move around obstacles. I want to reduce this motion and avoid obstacles primary with KUKA. Of course there will be motion of slider but not so large. Can I set weight of this DOF for minimization translational motion? How can I do it in KDL or TRAC-IK or in planner?

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answered 2017-08-25 06:26:34 -0500

rbbg gravatar image

updated 2017-08-28 00:59:35 -0500

RRT-Connect doesn't do any weighting on any of the axis, so that is not possible with that planner.

In order to penalize slider movement with OMPL planners, you would need to use one of the optimal planners (Like RRT*, PRM*, etc). You would then need to write a custom cost function that assigns a lower cost to small slider movements. While this would certainly be possible, I am not sure how the performance would be, but certainly (a lot) slower than RRT-Connect. If you are planning for pose targets, you will also still be dependent on the quality of your IK solution, and I don't know whether any of the IK solvers support weights on the axis.

Perhaps something like STOMP or CHOMP can be used to assign such costs, but I'm not sure.

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The new generalised cost function and constraint infrastructure that will be added to OMPL (Mark Moll described it in the last MoveIt maintainers meeting) might make this sort-of work more feasible, but it would also need to be exposed to MoveIt users.

gvdhoorn gravatar image gvdhoorn  ( 2017-08-25 07:41:45 -0500 )edit

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Asked: 2017-08-23 16:22:35 -0500

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Last updated: Sep 06 '17