How to add 2 revolute joints (universal joint) in between 2 links in urdf?

I wanted to know if it is possible to add 2 revolute joints at same location in between 2 links. I was just curious to know how to design human shoulder and arm, as it has multiple DoF at several joints.

Asked by aarsh_t on 2022-01-25 06:49:39 UTC

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Hi @aarsh_t, I took this example from NAO URDF description as an example of a shoulder with 2 revolute joints for one possible solution: https://github.com/ros-naoqi/nao_robot/blob/master/nao_description/urdf/naoV50_generated_urdf/nao.urdf

Notice there are 2 joints of type revolute: RShoulderPitch and RShoulderRoll for the right shoulder.

RShoulderPitch joint with parent torso and child RShoulder
RShoulderRoll joint with parent RShoulder and child RBicep

Asked by osilva on 2022-01-25 09:17:27 UTC

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I see, I was rather looking for something like universal joint at one point with only 2 links rather than adding one extra link in between because I already have model with kind of ball-socket joint. During my search I found out it is not possible to have 2 perpendicular axis joint in gazebo for the same links.

Asked by aarsh_t on 2022-01-26 01:01:21 UTC