How to create pure torque source? d->qfrc_applied and d->ctrl

Discussion in 'Simulation' started by Jongwoo Lee, Apr 26, 2018.

  1. 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 -

    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?
    Last edited: Apr 26, 2018
  2. Emo Todorov

    Emo Todorov Administrator Staff Member

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