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I currently have a URDF that contains a robotic arm without any gripper. I am using pydrake to perform inverse kinematics for the arm but would like to attach a dummy frame to the end in order to constrain the position of the gripper rather than the position of the arm itself. I assume that I should use the function WeldFrames() but how can I set up the ghost gripper frame for this use?

Note: I may use multiple types of grippers and would therefore like to do this programmatically instead of changing the URDF directly.

Thanks!

Dani Lerner
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1 Answers1

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If I understand you correctly, you have an arm (without a gripper) in urdf, and separate urdfs for the various grippers. You could weld the gripper to the last link directly in the link coordinates -- see here for an example.

If you want to add another frame to that final link, for instance to indicate the mounting plate for the end-effectors, you can add that to the arm's urdf and weld in that frame instead. Here is an example of that.

Russ Tedrake
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  • Thank you so much for your help! I realized that the gripper urdf was not worth using so I just created a `FixedOffsetFrame()` and used `plant.AddFrame()` to the model instead of merging the gripper urdf. – Dani Lerner Jul 29 '21 at 14:44