Description
Intro
Hi!
I am a graduate student at HKU, I use MuJoCo for my research on robotic manipulation.
My setup
MuJoCo 3.3.0, Python and C, Linux
What's happening? What did you expect?
In the simple scenario attached below, the system initially evolves with low velocity and force before contact occurs. However, once contact happens, the simulation diverges rapidly. The immediate cause appears to be large contact force, but I am struggling to understand how such forces are generated, especially given the conventional yet specific setting combination used in the model.
I experimented with different options to mitigate the divergence, and found that some settings help (but inapplicable or impractical) while others do not:
- Helpful: Very small timestep (1e-5), pyramid friction cone, frictionless contact, RK4 integrator
- Unhelpful: Joint damping (unless set to a very large value), armature, friction loss, range, all other integrators
Steps for reproduction
Load the model below. Set actuator control to 1. Wait until contact happens.
Minimal model for reproduction
<mujoco>
<compiler angle="radian"/>
<option timestep="0.001" integrator="implicitfast" cone="elliptic" gravity="0 0 0"/>
<worldbody>
<body name="1" pos="0.05 0.3 0">
<joint name="1" axis="0 1 0" />
<geom type="capsule" size="0.1 0.5"/>
</body>
<body name="2">
<joint name="2" axis="1 0 0" />
<geom type="capsule" size="0.1 0.5"/>
</body>
</worldbody>
<actuator>
<motor name="2" joint="2" ctrllimited="true" ctrlrange="0 1" />
</actuator>
</mujoco>Code required for reproduction
No response
Confirmations
- I searched the latest documentation thoroughly before posting.
- I searched previous Issues and Discussions, I am certain this has not been raised before.