Changing PD gains of stiffness and damping for torque control

[jo-choi]

Hi, @Mayankm96 .

Thank you for your big help.

I have some related questions about changing the mode in a simulation.

Currently, I am running a simulation with my own imported robot gripper and would like to control the joints using torque (effort control). In my case, I want to use the torque control mode only during the grasping moment. So, I tried to set the values of stiffness and damping to zero (the initial setting is for position control). However, it doesn't work with the following code:

  set_gain_p = torch.tensor([[0.0, 0.0, 0.0]], device='cuda:0')
  set_gain_d = torch.tensor([[0.0, 0.0, 0.0]], device='cuda:0')
  robot.actuators["f_joint_3"].stiffness = set_gain_p
  robot.actuators["f_joint_4"].stiffness = set_gain_p
  robot.actuators["f_joint_3"].damping = set_gain_d
  robot.actuators["f_joint_4"].damping = set_gain_d

Also have a problem with zero PD gains at the initial setting. The joints do not control with the generated torques.

In Isaac Sim, I checked that the following works well:

switch_control_mode("effort", joint_indices=ids_gripper)
set_joint_efforts(efforts=torque_values, joint_indices=ids_gripper)

Is there any solution?

Thank you in advance.

[jo-choi]

Solved with set_joint_effort_target, write_joint_stiffness_to_sim, write_joint_damping_to_sim

Thanks