Is it possible to make several joints on one component?

[art1650]

Intro

Hello, I am studying at the university

My setup

My question

I wanted to try to teach my car to drive on its own in the simulator. but when I make a simultaneous rotation of the wheels in the 3D modeling program(fusion 360), one of the joints flies off in the simulator. but n fusion everything is fine
therefore, I have a question, is it possible to make the simultaneous rotation of the wheels mechanically, or is it possible to connect two connections only somehow in the simulator?
because as I understood one component cannot have two joints

Minimal model and/or code that explain my question

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[Balint-H]

Hello! Firstly a tip, in the Simulate window you can use the "J" key to enable visualising the joint axes in space, that can help you debug as well.

From the structure of it, to me it looks like you might need to set up joint equality constraints between the 4 hinge joints to essentially model the linkage.
See: https://mujoco.readthedocs.io/en/latest/XMLreference.html#equality-joint-m

Alternatively, you could close the kinematic loop with a weld constraint at the end so it doesn't fall down like this.
See: https://mujoco.readthedocs.io/en/latest/XMLreference.html#equality-weld-m

Out of these two options I think the first one is more elegant.