Design Method of IPMSM Using Multi-objective Optimization Considering Mechanical Stress for High-Speed Electric Vehicles

This paper proposes an optimal design method of interior permanent magnet synchronous motors based on multi-objective optimization including the mechanical stress for high-speed electric vehicles (EVs). Optimization design of motors for high-speed EVs is a time–cost challenge, requiring the resolution of multi-objective problems such as various performance targets and constraints across multi-physics. To improve the optimization efficiency, we introduce a sequential multi-physics handling method that consists of a two-step optimal process. In each step, specific design variables are selected based on their predominant influence on electromagnetic and mechanical characteristics, respectively. The chosen variables are then applied to each problem to optimize the objective functions with constraints. In the first step, optimization is carried out for the electromagnetic problems using comprehensive design variables, which are relatively coarse for addressing mechanical problems. In the second step, particularly relying on specific variables that mainly influence mechanical stress, optimization considering mechanical stress is performed with the final model of the first step. As a result, dividing the design process into two steps, complex high-dimensional problems are treated as low-dimensional problems that apply appropriate design variables for each physics problem. To simultaneously optimize and precisely evaluate motor characteristics, a multi-objective optimization, and the finite element method are employed in the design process. Finally, we verified the proposed method by designing an IPMSM for high-speed EVs that satisfies all requirements.