Design and Optimization of a Flux-Modulated Fault-Tolerant Permanent Magnet Rim-Driven Machine With Combined Stator to Improve Torque Density

In order to improve the torque density of traditional permanent magnet rim propulsion machine, a flux modulated fault-tolerant permanent magnet rim driven machine (FMFTPM-RDM) with combined stator is proposed, designed, and optimized in this paper. The combined stator originates from the open-slot stator and split-teeth stator. The key is adopting the combined stator with non-uniformly distributed flux modulation poles (FMPs) to yield multi-working harmonics and contribute to torque improvement. The expressions of back EMF and self-inductance of the proposed machine are derived by analytical method, and their effectiveness is proved by finite element analysis (FEA). Besides, leading geometric sizes influences on performances of the proposed machine are conducted. For obtaining the optimal geometric sizes quickly and accurately, response surface method (RSM) coupled with multi-objective genetic algorithm (MOGA) is adopted to optimize this machine. Afterward, comparative analysis of the proposed machine with traditional one is performed by FEA. It is concluded that the proposed FMFTPM-RDM has better performances such as higher torque density, lower torque ripple, and stronger fault-tolerant capability. Finally, a prototype is manufactured and the test results verify the proposed combined stator design.