Air-Gap-Domain Topology Optimization for Electromagnetic Vibration and Noise Reduction in an Interior Permanent-Magnet Motor

Electromagnetic vibration and noise become increasingly pronounced in high-power-density traction motors. This paper proposes harmonic-guided air-gap-domain topology optimization for a 48-slot, eight-pole interior permanent-magnet motor with hairpin windings. A normalized Gaussian network is used to parameterize the rotor-edge topology. NSGA-II then optimizes the network weights to adjust the characteristic flux-density harmonics in the air-gap-domain at the low-speed high-load (OC1) and high-speed light-load (OC2) operating points, while meeting torque, stress, and manufacturability requirements. Multiphysics simulations show a 57.52% reduction in $F_r(48,12f)$ at OC1. The $12f$ vibration acceleration decreases by 86.30% and 56.65% at OC1 and OC2, respectively, while the maximum sound-pressure level on the evaluation surface decreases by 1.04 and 1.75 dB. Average torque remains comparable to the baseline. Finally, a 40 kW prototype is tested to evaluate electromagnetic performance and vibration and noise characteristics.