Hi, I successfully set up the MuJoCo on Windows and now simulating human-robot interaction using C++. I was trying to add force and torque sensors between an arm exoskeleton and a human arm. The sites are supposed to be on 2-link arm exoskeleton. A 2-link human arm is programmed to push the exoskeleton at the sensors. The actuation control loop is to be later programmed. The documentation says "sensor/ force (*)" and "sensor/ torque (*)" output three numbers, which are the interaction force between a child and a parent body. I was a bit confused: since my exoskeleton and human arm are not child-parent related, what might be a good strategy to set up my .xml file? I tried adding one sensor A on exoskeleton (upper arm), and another sensor B on exoskeleton (lower arm, child of upper arm), but found the readings really big and always changing when simulated. I guess my .xml file is not in a logical kinematic tree. Or I should go with other sensor options? Thank you.