Inverse Dynamics from joint with Friction

I'm trying to do an inverse dynamics study, but I am also modelling the joints I want to get the torque from with friction.

I've used the SimScape Multibody Multiphysics Library to apply friction and limits to my revolute joint, similar to the image below. However, this functionality requires that I set the actuation torque to 'Provided by Input', and what seems like the resultant torque from friction and/or reaching the limits will be fed back in by the Hard Stop Friction block.

But I want to get the force required to actuate the joint as well, which according to documentation means I should set the actuation torque to 'Automatically Computed'.

Is there a way for me to get the torque required to actuate this joint according to some motion input while using this set up for friction?

Thank you in advance.

Answer 1

[Steve Miller]

Hi Sam,

If you are going to prescribe the motion this joint, then the friction force will have no effect on the joint's motion.

To get the answer you are looking for (torque to actuate including torque to overcome friction force),

1. Set Motion to "Provided by Input"
2. Set Torque to "Automatically Computed"
3. From the joint, sense the angle and angular speed, route that to the inputs of the friction block
4. From the joint, sense Actuator Torque
5. Add the output of the friction block and the joint output Actuator Torque to get the answer you are looking for.

--Steve