Deformable Cloth Simulation - Slipping Gradually

Discussion in 'Priority support' started by yujie, Jul 29, 2019.

  1. We have had some trouble with designing a Mujoco environment in which two grippers interact with a cloth. We are hoping to create an environment in which a robot gripper can hold a cloth for an extended period (ideally, at least a minute). We have tried many parameter settings as suggested by other Mujoco forum posts; the best settings for us are:

    Options: solver=“Newton”, impratio=”5”, cone=”elliptic”

    All geoms have friction='1.5 1.5 1.5', solref='0.01 1' solimp='0.99 0.99 0.01' condim='4'.

    For cloth, spacing="0.02" stiffness="0.02" damping="0.05".

    We’ve uploaded the xml files which contain all our parameters settings. However, the result is that the cloth still slips out of the gripper fairly quickly - here is the movie link

    We also tried the noslip solver (using 10 or more noslip iterations) but this leads to an unstable simulation. Reducing the timestep to 0.0001 doesn’t seem to help.

    Any advice on this would be greatly appreciated. Thank you very much!

    Attached Files:

  2. Emo Todorov

    Emo Todorov Administrator Staff Member

    Sorry about the delay. A small amount of slip over extended periods of time is unavoidable with soft contacts, unless you enable the no-slip solver. But that solver is not as stable, as you noticed. Are you sure it is important to you to avoid slip over extended periods of time? If so, I would suggest using the 2D grid composite object instead of the cloth object. It is modeled differently and the simulation is inherently more stable, so you should be able to use the no-slip solver and remain stable.