Hello all, I understand as the generalized force/torque applied to the system, and as the input to the actuator model which then generates generalized force/torque via actuator model. I am in the phase of playing with MuJoCo while testing a control algorithm of my interest. Therefore, it is better to have zero-actuator dynamics, i.e., to have pure torque/force sources as actuators. Is it possible to create a pure torque/force source? I assume that I need to implement - according to the notation in the documentation - http://www.mujoco.org/book/computation.html#geActuation dot{wi} = 0, and pi = ui ....which I don't know exactly how to implement. Can anybody provide me an advice or example? ---------------------------------------------------------------- Question 2: I have made my model that all joints have zero armature, zero stiffness, zero damping. This is a modification of the humanoid model given by the sample code. Would this make physical sense if I want to make actuator a pure torque source? added) this actually seems making QACC inf and stopped simulation. ---------------------------------------------------------------- Question 3: I think the best way to try 'pure torque source' is to directly specify d->qfrc_applied, instead of struggling with d->ctrl. Am I on the right track?

Assuming you define a motor (so that d->ctrl corresponds to force) the two approaches are equivalent.