A nonlinear PD controller for force and contact transient control

This article describes a nonlinear proportional and derivative (NPD) controller and its use for both non-contact transient force control (NCTFC) (zero velocity when contact occurs) and contact transient force control (CTFC) (non-zero velocity when contact occurs). The key advantages of NPD control are its high disturbance rejection and robustness to time delay. The authors present a gain design method for NCTFC. Simulations and experiments on the Sarcos Dextrous Arm show that PD control becomes unstable for CTFC while NPD control is stable and reaches the steady state quickly. Experiments with human subjects on NCTFC and CTFC are also presented.>