An experimental study of robot control during environmental contacts based on projected operational space dynamics

This paper addresses the problem of constrained motion for a manipulator performing a task while in contact with the environment, and proposes a solution based on projected operational space dynamics. The main advantages of this control technique are: 1) it exploits the environment contact constraint itself, so as to minimise the joint torques needed to perform the task; 2) it enables full decoupling of motion and force control; 3) force feedback from a force sensor mounted at the end effector or other contact points is not needed. This work is a step towards a robot control strategy which mimics the human behaviour of exploiting contacts with the environment to help perform tasks. We present an experimental implementation of the control method in which a KUKA LWR IV manipulator uses an eraser to wipe a whiteboard, and we show that this controller can effectively exploit contact with the whiteboard in order to reduce joint torques while still performing the desired wiping motion.