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X-Y axes for UR5 appear reversed

asked 2022-09-02 13:54:44 -0500

CroCo
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I'm trying to test a kinematic controller that relies on UR5 DH parameters. I'm using UR5 model in universal_robot and the classical DH parameters. The controller works but there is just one problem. The x-y axes are reversed. If I send 0.5i+0.5j+0.5k, the rviz shows -0.5i-0.5j+0.5k, see the below picture. You can see the the arm is going in the opposite direction of the x-y axes. How can I rectify this issue? I'm using Gazebo 9 and Melodic to simulate the robot. I really appreciate your help and feedback.

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answered 2022-10-17 09:58:34 -0500

Mike Scheutzow
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There are many different "families" of quaternion (not sure if family is the right word.) The family used by DH is different from the one that is used by ros, so they are not directly compatible. You need to convert the DH quaternion to get the equivalent ros quaternion.

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DH method represents the orientation as a Rotation matrix not quaternion, but I think you are right in the way tf tree is structured differs from the DH method. This deprives me from visualizing the frame of the end-effector sadly since modelling manipulators heavily rely on DH. Do you know how the tf internally constructs the tree? Thank you.

CroCo ( 2022-10-17 14:34:15 -0500 )edit

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Asked: 2022-09-02 13:54:44 -0500

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Last updated: Oct 17 '22

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X-Y axes for UR5 appear reversed