MATLAB: Simscape Multibody 2G // Change the direction of the axis of a joint primitive

Question

Hello,

The title says a lot, I found this example here (in section "directing joint axis") that explain how to do it in the 1G, but no idea how to do that in the second generation.

How can I for instance use a prismatic joint and decide that the primitive is along x and not along z ?

Thanks in advance, any tip would help a lot ):

Answer 1

The 2nd Generation joint blocks in Simscape Multibody define the primitive along one direction. For example, the Revolute Joint block represents a joint with one rotational degree of freedom along the common Z axis, as mentioned in the documentation:

https://www.mathworks.com/help/physmod/sm/ref/revolutejoint.html

You cannot change the primitive direction of rotation, but you can connect a Rigid Transform to the joint block. This change was made to add more flexibility in defining reference frames between solids and joints. Refer to the following documentation:

https://www.mathworks.com/help/physmod/sm/ref/rigidtransform.html

Here is an example that uses this technique rather than using First Generation blocks:

https://www.mathworks.com/help/physmod/sm/examples/computing-actuator-torques-using-inverse-dynamics.html