Could the value of Spring Stiffness in the Revolute joint block (Simscape) be variable?

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I'm trying to build an inverse dynamic model, where the * spring stiffness* is a variable value, or more specifically, a function of the input, the motion trajectory. How should I implement for this? Could someone give me any related examples or information? Thanks a lot!

Accepted Answer

Nicolas Schmit
Nicolas Schmit on 21 May 2018
The stiffness parameter of the revolute joint is a constant. You cannot change it in real time.
Here is how you can implement a variable stiffness:
  1. In the actuation tab, set the torque to "Provided by Input" and the motion to "Automatically Computed".
  2. In the sensing tab, activate the Position sensing.
  3. Create a feedback loop from the position sensing output to the torque input.
  4. In your feedback loop, place a function which calculates a torque as a function of the position. The derivative of your function with respect to the position will be the stiffness at a given time.
  3 Comments
FENGPEI YUAN
FENGPEI YUAN on 22 May 2018
I got your idea...but in my model, especially the inverse model, I need to actuate my mechanical system by Motion Input, where the spring stiffness is still dynamic. Therefore, I think of one solution, as shown in the attached picture... Moreover, if we monitor the actuator torque of the Revolute joint, I think it will work...

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