Electromagnetic–Structural Coupling Analysis and Optimization of Bridge-Connected Modulators in Coaxial Magnetic Gears

This study presents a comprehensive analysis and optimization methodology for bridge-connected modulators in coaxial magnetic gears. A novel harmonic modeling method incorporating magnetic saturation through permeability convolution matrices and multiple-layer radial subdivision is developed, achieving computational efficiency 20 times greater than finite element analysis with comparable accuracy (deviation < 3.2%). The research establishes an electromagnetic–structural coupling framework that captures the complex interactions between the magnetic field distribution and mechanical deformation, revealing critical trade-offs between electromagnetic performance and structural integrity. Multi-objective optimization using an improved NSGA-II algorithm identifies Pareto-optimal solutions balancing torque density, structural safety, efficiency, and thermal stability. Experimental testing validates that bridge width ratios between 0.05 and 0.07 provide optimal performance, delivering torque densities exceeding 80 kNm/m3 while maintaining stress ratios below 0.65 of material yield strength. Thermal analysis demonstrates that optimized configurations maintain operating temperatures below 70 °C with reduced thermal gradients. Vibration characteristics exhibit a strong correlation with bridge width, with wider bridges providing enhanced stability at higher speeds. The findings establish practical design guidelines for high-performance magnetic gears with improved reliability and manufacturability, advancing the fundamental understanding of electromagnetic–structural interactions in field-modulated magnetic gear systems.