Control Performance Improvement of PMSM Direct-Drive Servo System at Low Speeds

In this article, to improve the speed control performance of PMSM direct-drive servo systems under low-speed operation, a composite control strategy based on rotor position tracking control (RPTC) and deadbeat predictive current control (DPCC) is proposed, and a dual-loop control framework is established for the position loop and current loop. RPTC converts the speed command into real-time rotor position trajectory to smoothly track the rotor position, which can effectively eliminate the speed calculation error, and the strategy shows good speed following performance and anti-disturbance capability in low-speed conditions. The DPCC based on the “two-step prediction” is used to compensate for the effect of control delay, and the influence of inverter nonlinear factors is reduced by deadtime compensation, which effectively improves the dynamic performance of the current loop and further enhances the speed control performance under low speed. The efficacy of the proposed composite control strategies is validated through the presentation of extensive comparative simulations and experimental results.