Design Optimization of Hybrid Magnet CMGs with Non-Uniform Air-Gap Considering Demagnetization Analysis

This paper introduces two novel designs and an optimization methodology for hybrid flux-focusing Halbach coaxial magnetic gears (HFH-CMGs) that strategically integrate cost-effective ferrite and high-energy rare-earth permanent magnets (PMs). The distinct electromagnetic and material properties of these PMs significantly impact torque transmission performance. A comprehensive demagnetization analysis of the proposed configurations is conducted using the magnetic equivalent circuit (MEC) approach and the B-H curves of both PM types. To enhance performance while minimizing reliance on rare-earth materials, a multi-objective optimization framework is developed, incorporating torque density, cost considerations, and irreversible demagnetization constraints to ensure an optimal trade-off between efficiency and operational reliability. Given the computational demands of the optimization process, a surrogate-assisted approach is implemented, leveraging the Kriging method in combination with the non-dominated sorting genetic algorithm II (NSGA-II). This approach yields a set of Pareto-optimal solutions, from which the most suitable design is selected. The final optimized configuration is then evaluated through finite element analysis (FEA) to validate its performance. The FEA results confirm that the proposed optimization strategy effectively enhances torque density and demagnetization resistance, ensuring stable operation under peak torque conditions.