New results in NPID control: Tracking, integral control, friction compensation and experimental results

Nonlinear proportional-integral-derivative (NPID) control is implemented by varying the controller gains as a function of system state. NPID control has been previously described and implemented, and recently a constructive Lyapunov stability proof has been given. Here, NPID control analysis and design methods are extended to tracking, and to systems with state feedback and integral control. Experimental results are presented showing improved tracking accuracy and friction compensation by NPID control.