Computation of the forces between rigid and soft bodies with joint data

Hello everyone,

I’m using Isaac Sim 4.2 to simulate and measure forces through deformable bodies (that I simulate with CUDA since with CPU is not possible). Specifically, I have a cylinder with deformable body properties that is attached to a rigid body using a fixed joint. Initially, I tried creating a fixed joint between the deformable cylinder and the rigid body. To test this setup, I dropped a cube with a certain mass onto the structure and used the [get_measured_joint_forces] function to retrieve the 6D forces.

However, I encountered several issues:

  • The joint function doesn’t seem to work as expected. Although the function executes, the force values are incorrect since the mass of the cube isn’t detected.
  • Additionally, the sensor behaves abnormally, flying into space and failing to stay grounded even with gravity enabled.

After researching how to attach deformable bodies to rigid ones, I realized I should use an “attachment.” This resolved the gravity issues. Now, I have attached two rigid bodies using a joint to read force data via the function, and I attached the second rigid body to the deformable body. However, the data I receive is still inaccurate, as it doesn’t detect the impact when the cube collides with the setup (see picture).

Interestingly, when I replace the deformable cylinder with a rigid body, the force values are accurate and behave as expected.

Does anyone know how I could resolve this issue? Has anyone faced similar challenges or have suggestions for fixing this behavior?

Hey @milan.francois.t.amighi! Could you please try Isaac Sim 4.5 and see if this issue persists?

Hello @zhengwang, just try it and it doesn’t work even with version 4.5 of Isaac Sim.