The user functions set the specific behavior of your multibody system. This behavior is controlled by several actions for instance:
Introducing the torque/force due to an actuator, see
Imposing the trajectory of a specific joint (regardless the force required), see
Creating a constraints between joints (i.e. gears), see
The complete list of user functions is available below.
In the following list, the module containing the function is the name of the file defining the function.