Multi-Objective Optimization and Analysis of Two-Degree-of-Freedom Flux-Switching Permanent Magnet Machine

Two-degree-of-freedom flux-switching permanent magnet (2DoFFSPM) machines can directly drive loads to realize rotary, linear, and helical motions. They therefore provide a compact solution for multi-dimensional direct-drive systems. However, the double-salient stator–mover structure and end effects cause large torque and thrust ripples, reducing motion stability and positioning accuracy. This paper presents a multi-objective optimization of a 2DoFFSPM machine under helical operation. Average torque, torque ripple, average thrust, and thrust ripple are selected as optimization objectives. Four key structural parameters are selected as optimization variables. The Taguchi method is used to construct the orthogonal design. Three-dimensional finite-element analysis (3D FEA) is then performed under helical operation to evaluate the optimization objectives. The optimized design reduces torque ripple and thrust ripple by 47.3% and 48.38%, respectively, and increases average thrust by 8.1%, with only a 1.1% decrease in average torque. These results demonstrate that the proposed method achieves a balanced improvement in output capability and motion stability under helical operation.