Object manipulation pipeline: how to motion plan with the hand, but grasp without it...?

Question

Hi all,

Tabletop Manipulation seems to be structured such that object_manipulator plans grasps by removing the table from the Planning Scene, or at least disabling collisions between the gripper links and the table.

The result is, that after planning a grasp, if you try to plan a motion around the table (say, from underneath it) the gripper is not included in the planning process and collides into the table!

• Has anyone had this problem?

• Can anyone suggest how to re-enable the gripper to plan motions for the arm, whilst still allowing the the gripper to get close to the table surface?

(one 'hack' that comes to mind, is leaving a single row of voxels at the front edge of the table)

Many thanks :-)

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Originally posted by dbworth on ROS Answers with karma: 1103 on 2013-02-27

Post score: 0

Answer 1

That is odd. The table ought to be added to the planning scene separately, which would result in the gripper avoiding the table properly. Does the table show up as a polygon when you display the planning scene topic in rviz? If not, it's not being added to the planning scene. (You can add it using processCollisionGeometryForTable in collision_map_interface.cpp in the tabletop_collision_map_processing package.)

If the table is in the planning scene, then the move to the pre-grasp pose should be avoiding colliding with it. Disabling collisions between the grasp and the table is only done when checking for collisions with the final grasp pose, not the pre-grasp pose. So the pre-grasp pose should not be in collision with the table. We use move_arm to get to the pre-grasp pose, with collisions enabled between the gripper and the table, so there shouldn't be any collisions there.

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Originally posted by hsiao with karma: 741 on 2013-02-28

This answer was ACCEPTED on the original site

Post score: 1