Tooth-Wise Rolling-Direction Design of Grain-Oriented Electrical Steel for Thrust Enhancement and Thrust Ripple Suppression in Permanent Magnet Linear Synchronous Motor

Abstract Permanent magnet linear synchronous motors (PMLSMs) used in high precision applications demand both high thrust density and minimal thrust ripple. This paper presents a novel tooth-wise rolling direction design using grain-oriented electrical steel (GOES) to create a spatially tailored permeance profile in the mover core. The core principle is to strategically assign the GOES easy axis to enhance fundamental, thrust producing flux paths while utilizing the hard axis to suppress the specific spatial harmonics responsible for thrust ripple. A theoretical framework linking spatial harmonics to thrust ripple is established. Based on this, both a conventional uniform direction GOES model and the proposed tooth-wise design were optimized using a multi objective genetic algorithm (NSGA-II) to ensure a fair comparison. Finite element analysis results demonstrate that the proposed design reduces the simulated thrust ripple from 3.60% to 1.79% while maintaining average thrust. Analysis of the no-load voltage waveform and the local force density at minimum thrust points reveals that this improvement stems from the strategic rebalancing of the air gap flux density components, which mitigates causes of ripple. Furthermore, acknowledging the manufacturing complexity of the ideal segmented core, a practical implementation method using stacked sets of non-segmented laminations, termed Stacked Heterogeneous Anisotropy Core (SHAC), is proposed and validated. This approach aims to approximate the performance benefits of the tooth-wise design with a more scalable manufacturing process. This study, therefore, introduces an effective structural design methodology that leverages material anisotropy to actively control electromagnetic performance in high precision PMLSMs and presents a practical strategy for its implementation.