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Question How should I be setting stiffness / damping parameters for articulation bodies?

Discussion in 'ML-Agents' started by superweeniehutjr, Jan 14, 2023.

  1. superweeniehutjr

    superweeniehutjr

    Joined:
    Apr 8, 2021
    Posts:
    5
    I'm using articulation bodies for a 'walker' type setup and they're controlled as PD motors in physx, with stiffness being Kp / the P gain (aka what the proportional difference is scaled by) and the damping being Kd / D gain (aka what the derivative, velocity, difference is scaled by)

    I can't find a good resource for finding what the values of these settings are. I set my human up with capsules and set the mass of each body based on the average human mass (of 980 some kg/m^3) but I can't find an equivalent heuristic for to use for the PD motors.

    I saw https://github.com/Unity-Technologies/marathon-envs has a similar setup to mine and there PD gains seemed pretty arbitrary.
     
  2. GamerLordMat

    GamerLordMat

    Joined:
    Oct 10, 2019
    Posts:
    186
    hello,

    PID controller values have nothing to do with any physical units. They are just parameters that tune your system, they are a signal that you have to interpret. The amount of force that is produced is up to you, or in this case their is a parameter called something like "angular force/drive" (or something like that).
    So how much torque a human joint can produce is surely somewhere in the internet, or calculate it yourself somehow.