Thrust Ripple Suppression Strategy for Precision Machining Platform by Using Predicted Current Sliding Control

Abstract

This paper focuses on solving the problem of the thrust ripple of the permanent magnet linear synchronous motor (PMLSM) to improve the machining accuracy and stability of the precision platform. The air gap magnetic field model of the permanent magnet magnetic field and the armature permanent magnet magnetic field are established using the equivalent magnetization method and the equivalent current method. The mathematical model of the linear motor is then derived using Clark and Park coordinate transformation. Also, the dynamic equation of the linear motor is developed considering the influence of electromagnetic thrust, detent force, and friction force. The error expressions resulting from thrust ripple are provided. To eliminate the thrust ripple and enhance the accuracy of the linear motor, a linear thrust observer is utilized to compensate for the low-frequency thrust ripple. The compensation current for the thrust ripple is then incorporated into the servo system using a new sliding mode controller. Additionally, a double T-Notch filter is designed to eliminate the interference signal caused by occasional resonance at a specific frequency, thereby ensuring the stability of the system output. Finally, experimental validation is conducted to verify the effectiveness of the proposed strategy, and the results demonstrate a significant improvement in thrust fluctuation and tracking accuracy.