Repetitive tracking control of a coarse-fine actuator

This paper discusses the repetitive tracking control method for a coarse-fine actuator which is implemented on the existing PID controller augmented with feedback linearization loop. The proposed positioning system is composed of a magnetic linear drive as a coarse actuator and a piezoelectric linear positioner as a fine actuator. In particular, the nonlinear friction in a magnetic linear drive and the hysteresis characteristic of a piezoelectric linear positioner are modeled. The feedback linearization loop uses these models in tracking position control. The control strategy is then further extended to include a repetitive control algorithm in tracking periodic inputs. The experimental results show that the performance in tracking sinusoidal waveforms is noticeably improved by augmenting a PID controller together with feedback linearization loop and a repetitive controller.