Nan, Inf or huge value in QACC at DOF 30. The simulation is unstable. Time = 9.6540.

Discussion in 'Support requests' started by Sridhar Thiagarajan, Jul 9, 2019.

  1. <option timestep="0.002" solver="CG" tolerance="1e-6"/>

    <size nconmax="700" njmax="3000" nstack="1000000"/>

    <worldbody>

    <body name="B3_5" pos="-0.05 0 1">
    <freejoint/>
    <composite type="cloth" count="9 9 1" spacing="0.05" flatinertia="0.01">
    <skin material="matcarpet" texcoord="true" inflate="0.005" subgrid="2"/>
    <joint kind="main" damping="0.001"/>
    <joint kind="twist" damping="0.001"/>
    <geom type="capsule" friction="0.1 0.005 0.0001" size="0.015 0.01" rgba=".8 .2 .1 1"/>
    </composite>
    </body>

    </worldbody>

    When I apply somewhat high forces in simulate.cpp for this model, or use this model along with a fetch robot. I got the Inf error above. Do I have to simulate at even lesser time resolutions if I want to avoid this error? Are there other alternatives?
     
    Last edited: Jul 9, 2019
  2. Emo Todorov

    Emo Todorov Administrator Staff Member

    It is better to use the Newton solver, since it has much higher accuracy. If the simulation is going unstable, you can reduce the time step or increase joint damping.

    Note that grids are generally better behaved than cloth, even though they are more limited in what can be modeled.