Design and Optimization of an Outer-Rotor PMSM for Torque Ripple Minimization

This paper presents a design optimization process for a surface-mounted permanent magnet synchronous motor (SPMSM) that aims to minimize torque ripple while simultaneously satisfying multiple design objectives and constraints. The study begins by analyzing the torque ripple mechanism through mathematical analysis of the instantaneous torque components, followed by a review of various mitigation techniques. The selected mitigation techniques are then applied to a 200 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{W}$</tex> external rotor baseline model using a surrogate-based design optimization framework. The goal is to optimize key performance metrics such as torque density, efficiency, and cost while reducing torque ripple. Finite element analysis (FEA) results confirm that the optimized design significantly outperforms the baseline in all performance metrics, with an 82<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> reduction in cogging torque and an 80% reduction in torque ripple.