Can we get joint axis?

[keiohta]

Hi author, I want to know a joint axis but haven't figured out how to do that. It seems provided methods do not include such functionality, so opening this thread. So, is there any possible way to get a joint axis from a PyJoint object?

I imagine if a URDF is like:

    <joint name="joint_1" type="revolute">
        <origin xyz="0 0 0" />
        <axis xyz="0 0 1" />
        <child link="link_1" />
        <parent link="link_0" />
        <limit lower="0.0" upper="3.141592653589793" />
    </joint>

then I can get (0, 0, 1) when we call a method like joint.get_axis().

Thanks in advance for your continuous support.

[fbxiang]

You can use joint.get_parent_link().pose * joint.get_pose_in_parent() to get the frame of this joint. The x axis of this frame is the joint direction, and the position of the frame is the joint origin. For example, you can extract the direction by pose.to_transformation_matrix()[:3,:3] @ [1,0,0]

[keiohta]

Your answer completely solved my issue. Thank you!!