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Hi All,

I have a dual arm biped system as shown in MoveIt here: image description

The system works by having one arm grasping a support whilst the other reaches out for another. Switching between the two, locomotion is carried out.

The problem i have is that I have only been able to move the robot from the same gripper, i can't switch which one is stationary from which the rest of the joints should be calculated.

How can I plan trajectories for this system?? I intended to plan from one gripper, obtain a new support, change the fixed gripper to the other side, the plan again from this new point.

Any help is much appreciated.

Regards,

Chris.


Originally posted by anonymous8676 on ROS Answers with karma: 327 on 2014-10-10

Post score: 1


Original comments

Comment by Airuno2L on 2014-10-11:
I haven't used Moveit! much but have you tried making two separate move groups? E.g. one's base link is one gripper, and the other's base link is the other gripper.

Comment by anonymous8676 on 2014-10-16:
Given that this system actually matches the legs of a humanoid biped from the waist down, is it possible to use their approach? How do users do planning for the humanoids?

Comment by Airuno2L on 2014-10-20:
I believe they do as I was suggesting, using different move groups.

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1 Answer 1

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I don't think MoveIt, or even the underlying URDF/SRDF formats can actually describe this without at least some hacking.

If I had to do this, I think I would rely on an external "odometry" node that would track the position of the "base gripper" in the "world link" and output a TF transformation. When the base gripper is closed on something, the TF transform obviously would not change, however, when the other gripper is closed and the arm is moving, the transform would be updated based on how far the "base gripper" has moved. MoveIt would only ever have a single planning group, from the "base gripper" to the "other gripper" and (heres the other hacky part), when specifying a cartesian goal when the "other gripper" is closed, you would actually specify the inverse movement that you want to do with the "base gripper".


Originally posted by fergs with karma: 13902 on 2014-10-12

This answer was ACCEPTED on the original site

Post score: 1

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