Does anyone know how to switch a joint between having a prescribed motion driver and acting as a passive joint? More specifically, I am building a bed of spring to serve as a model for haptic feedback on a Phantom Omni device. Therefore, I need to read the position of the device (which is not a problem) and then based on the position of the device calculate a force to feed back to the device.

Consider the simplified example below. In one situation I may need to give...