Optimal design of fault-tolerant outer-rotor spoke-type PMSM with single-layer FSCW and magnetic notches using Kriging and NSGA-2 for satellite CMGs

The satellite industry is shifting from large monolithic satellites to small-satellite constellations, resulting in increased requirements for high reliability and mission longevity. The attitude and orbit control system (AOCS), a key subsystem, employs control moment gyroscopes (CMGs) driven by permanent magnet synchronous motors (PMSMs) for continuous high-speed operation. This study proposes a fault-tolerant (FT) outer-rotor spoke-type PMSM featuring a single-layer fractional-slot concentrated winding (FSCW) and a ferrite-based magnetic notch. The single-layer FSCW enhances electromagnetic phase decoupling through the introduction of uncoiled teeth. The magnetic notch functions as a flux barrier that reduces inter-phase mutual inductance while preserving air-gap flux density. An ordinary Kriging surrogate model is employed as a computationally efficient alternative to the finite element method (FEM), and multi-objective optimization is conducted using the Non-dominated Sorting Genetic Algorithm 2 (NSGA-2). The optimized design achieves reductions of 63.20 % in cogging torque, 46.66 % in torque ripple, 28.37 % in mutual inductance, and 39.89 % in flux linkage deviation. All reported performance improvement is expressed as a relative value with respect to the conventional model. The results confirm the effectiveness of the proposed motor in enhancing the electromagnetic fault tolerance of CMG systems.