Analysis and Suppression of Normal Force Ripple for Long Primary Permanent Magnet Linear Synchronous Motor

This paper proposes a double-side long primary permanent magnet linear synchronous motor (PMLSM) that can operate in suspension. In this motor, the levitation subsystem and propulsion subsystem are decoupled in terms of both “electrical circuit” and “magnetic circuit”, resulting in lower system control complexity. For this motor, the normal force between the primary and secondary components is a major component of the motor's levitation force. The normal force ripple can hinder improvements in system positioning accuracy and operational stability. This paper investigates the characteristics of normal force ripple in this motor, establishes a model for local normal force calculation and simulation analysis, and reveals the influence mechanism of end effects and armature reactions on the normal force ripple. Based on this, an optimized design solution for split-ended magnetic pole is proposed, effectively suppressing normal force ripple, both locally and whole. Finally, for a 24-slot 8-pole prototype, finite element simulation and experimental tests are conducted. The results show that no normal force ripple in both local and whole aspects of the motor, validating the theoretical research presented in this paper.