Research on No-Load Air-Gap Magnetic Field and Multi-Objective Optimization of a Three-Segment Halbach PMSLM With Partially Magnetized Poles

Abstract

A three -segment Halbach permanent magnet synchronous linear motor with partially magnetized poles (PTH-PMSLM) is proposed to address the thrust ripple issue in permanent magnet synchronous linear motor (PMSLM). The proposed motor features a coreless mover structure, adopts a three-segment Halbach array for the permanent magnet arrangement, and uses convex iron poles to replace part of the main magnetic poles, which reduces leakage flux harmonics and increases magnetic flux density. Additionally, since different topologies affect the motor performance, a subdomain analytical model is established to systematically analyze the influence of key structural parameters on motor performance. To reduce computational effort and improve model accuracy, a Kriging multi-objective coati optimization algorithm (Kriging-MOCOA) model is used to optimize the magnetic pole structure, with average electromagnetic thrust, thrust ripple, thrust density, and no-load back electromotive force (EMF) as optimization targets. The Pareto front is obtained using the expected improvement (EI) infill criterion, and the optimal parameter combination is determined. It is demonstrated that the proposed motor exhibits lower thrust ripple and higher permanent magnet utilization, as validated by the developed analytical model and finite-element results. This design is suitable for high-precision machining equipment.