This is a file meant to be included in other MuJoCo model. An example is in this repository: https://github.com/griloHBG/Rover4We.
The model implements both ackerman steering geometry and rear differential drive.
- first one is done with equality constraints between the ghost-steer-wheel (like a steering wheel, visible over the rover) and both the front wheels (f-r-wheel and f-l-wheel).
Many thanks to Emo Todorov's answer on this MuJoCo's Forum thread: http://www.mujoco.org/forum/index.php?threads/implement-differential-drive-in-mujoco.3367/#post-3620
- last one is done with a motor attached to a fixed tendon (http://www.mujoco.org/book/XMLreference.html#fixed) that is coupled with both rear wheels (r-r-wheel and r-l-wheel)
This resource can also provide a help to this thread: http://www.mujoco.org/forum/index.php?threads/any-plan-to-release-a-simple-car-model.3751/#post-5633