Design Optimization of a Highly Integrated Magnetic Gear Motor Assembly

Magnetic gear integration with permanent magnet machines offers significant advantages for electric drivetrains, combining the benefits of contactless torque transmission, unlike mechanical gear systems, with the compactness and efficiency improvements over direct-drive motors. This paper introduces a highly integrated magnetic gear motor assembly (MGMA) that incorporates an interior permanent magnet (IPM) motor and a coaxial magnetic gear (CMG), thereby reducing system volume and enhancing torque density. Compared to conventional radially integrated magnetic-geared motors, the proposed topology offers a mechanically robust and structurally reliable alternative achieving higher efficiency and a higher torque density. The paper details the operating principle and structural configuration of the proposed MGMA. A comprehensive three-stage multi-objective optimization framework, leveraging a surrogate-assisted non-dominated sorting genetic algorithm II (NSGA-II), is employed to maximize output torque while minimizing both torque ripple and PM usage. Moreover, the efficiency maps and thermal analysis of the proposed MGMA are investigated in detail. A prototype of the optimized design is fabricated and experimental investigations have been conducted to verify the effectiveness of the proposed design.