An Observer-Based Mode Switching Control Scheme for Improved Position Regulation in Servomotors

A mode switching control scheme is proposed to achieve fast and precise set-point tracking in motor servo systems. The control scheme incorporates a composite nonlinear feedback (CNF) control law into the framework of proximate time-optimal servomechanism (PTOS). The CNF control law consists of a linear feedback part for achieving fast response and a nonlinear feedback part for suppressing the overshoot, so as to improve the transient performance in short span positioning, while the PTOS control law is responsible for fast acceleration and deceleration when the tracking error is large. A reduced-order extended state observer is designed to estimate the unmeasured velocity and unknown disturbance for feedback and compensation. The closed-loop stability is analyzed theoretically. The control scheme is then applied to the position-velocity control loop in a permanent magnet synchronous motor servo system. Experimental studies have been carried out using the TMS320F2812 digital signal controller board. The results verify that the controlled system is capable of tracking a wide range of target positions fast, smoothly, and accurately, with some degrees of performance robustness against disturbance and uncertainty.