Acceleration feedback and friction compensation for improving positioning performance in systems with friction

High-gain proportional-integral-derivative (PID) position control can achieve stiff position control but it involves the risk of overshoots in some cases such as discontinuous position commands and disturbances. This paper presents a new position controller that achieves accurate trajectory tracking and overdamped resuming motion from large positional errors and disturbances. The proposed controller is a combination of PDD² (proportional, derivative, and second derivative) controller with nonlinear D² term, which we call (N-PDD²), and the output of a friction compensator (FC). The nonlinear D² term allows the use of high gain PDD² and thus, advantageous in dealing with disturbances. Accurate trajectory-tracking is achieved due to friction compensation. The validity of the proposed controller was demonstrated through experiments in realizing overdamped motion and accurate tracking simultaneously and achieving improvement in robustness to disturbances in a robotic manipulator.