I did another test to make sure that what I mentioned is correct, I set the Dof properties as
props[“driveMode”].fill(gymapi.DOF_MODE_EFFORT)
props[“stiffness”].fill(1.0)
props[“damping”].fill(0.0)
props[“friction”].fill(0.0)
And then applied a 10NM effort input like this:
if(frame_count<100):
efforts = np.full(num_dofs, 10.0).astype(np.float32)
gym.apply_actor_dof_efforts(envs[0], handles[0], efforts)
if(frame_count>=100):
efforts = np.full(num_dofs, 0.0).astype(np.float32)
gym.apply_actor_dof_efforts(envs[0], handles[0], efforts)
after putting the effort to 0, the joint moved back to its original position as if it’s pulling back by a spring with similar behavior. so in effort mode the stiffness is like spring attached to the joint. I haven’t tested other modes yet though based on the documents, they work like PID parameters.