A flux weakening control algorithm for permanent magnet synchronous grinding electric spindle based on sliding mode controller

This paper proposes a leading angle flux-weakening speed regulation strategy based on sliding mode control for surface-mounted permanent magnet synchronous motorized spindle (PMSMS). The traditional flux-weakening control strategy suffers from problems such as low-speed jitter and a narrow range of speed control. To address this issue, the proposed strategy uses a sliding mode controller instead of a PI controller to adjust the speed error and eliminate poor control performance. The sliding mode controller introduces an integral term and uses the hyperbolic tangent function to make the sliding mode switch smoother, reducing the “jitter” phenomenon and improving system control quality. The strategy also uses a three closed-loop control of the speed, current, and voltage, where the motor terminal voltage and the DC side voltage form the voltage control loop, producing the motor current field. Experimental results show that the leading angle flux-weakening speed regulating strategy based on sliding mode control has better dynamic characteristics at higher speed ranges. It improves the spindle starting process efficiency by nearly 60%, and suppresses stator current oscillation and torque ripple. Moreover, the stator current of the direct axis and the intersecting axis is significantly smaller than that of the conventional control strategy during steady speed, while the transition process is smoother, which is more conducive to subsequent high-precision machining processes. The proposed strategy improves the speed regulating performance of the permanent magnet synchronous motorized spindle, realizing high-quality drive and operation of the spindle unit.