OSC_POSE controller coordinate systems

[samarth-robo]

Hi, thanks for open-sourcing this library!

I am trying to figure out the coordinate systems used by the OSC_POSE controller. I have control_delta = True. So ideally it is the EEF coordinate system -- Z out of the gripper, Y perpendicular to the gripper motion. But I am not observing that.

I test by applying small translations and rotations continuously and observing the robot motion.

Translation

Setting action = [0.01, 0, 0, 0, 0, 0, -1], [0, 0.01, 0, 0, 0, 0, -1], or [0, 0, 0.01, 0, 0, 0, -1], I observed the following motions:

Rotation

Around X axis, action = [0, 0, 0, np.deg2rad(1), 0, 0, -1]

Around Y axis, action = [0, 0, 0, 0, np.deg2rad(1), 0, -1]

Around Z axis, action = [0, 0, 0, 0, 0, np.deg2rad(1), -1]

• It seems like the translation axes are different from the rotation axes
• Neither of them seem to be following the expected EEF coordinate system mentioned in assets/robots/panda/robot.xml. The translation axes seem to be the world axes, and rotation axes are also unexpected.

Relevant code snippets:

controller_configs = load_controller_config(default_controller='OSC_POSE')

# self is derived from SingleArmEnv
while True:
  action = np.array([0.01, 0, 0, 0, 0, 0, -1])  # or other values mentioned above
  obs, _, done, _ = self.step(action)
  self.render()

[samarth-robo]

It was a fault in my understanding of operational space control. The relative actions are still applied in the world coordinate frame, not the EEF coordinate frame.