Nonlinear proportional and derivative control for high disturbance rejection and high gain force control

A non-model-based, nonlinear proportional-and derivative (NPD) controller for high disturbance rejection and high-gain force control is introduced. The controller actively raises the damping and stiffness exponentially when the motion is in an unfavorable direction. Design and analysis are given for a second-order system. Theoretical and experimental comparisons to a conventional proportional-and-derivative (PD) controller show that the NPD controller gives better performance in disturbance rejection for position control and in transient response for high-gain control