Design of Improved Finite-Time Composite Controller for PMSM Servo System Under Position and Speed Single-Loop Structure

The conventional position servo system usually adopts the position-speed-current three closed-loop control structure. Although each loop variable can meet the expectation, the bandwidth of the outer loop is restricted by the inner loop, which affects the dynamic performance of the outer loop. In this article, a finite-time position-speed single-loop controller was designed to improve the position control performance. Meanwhile, an improved speed-constrained function is proposed to address the issue of uncontrolled speed in position-speed single-loop structure. Moreover, a high-order disturbance-separated finite-time disturbance observer is designed to estimate the disturbance, and a small-gain finite-time integral term is proposed to improve the speed and accuracy of disturbance estimation. Finally, the proof and parameter design principles of the proposed method are presented, and its effectiveness and superiority are experimentally verified.