Robust nonlinear controller for PMLSM feed drives in grinding machines

A globally stable nonlinear controller was introduced into a permanent magnet linear synchronous motor(PMLSM) feed drive to eliminate the large model uncertainties and disturbances.To enhance the stability and tracking performance,the nonlinear controller fully utilizes the signals such as the position tracking error and its integral position tracking error,the velocity and its error and the second derivative of the reference input.Then a Lyapunov function was constructed to verify the stability of the nonlinear controller.Simulations and experimental results show that the tracking error and the speeding response of the nonlinear controller is much superior to those of the traditional nested PI controller;that the nonlinear controller is robust to model uncertainties and disturbances;and that the velocity fluctuation is small for different cutting depth in the grinding.