Performance enhancement of underwater propulsion motor using differential evolution optimization

Abstract

This paper describes the performance enhancement of underwater propulsion motor using differential evolution optimization (DEO). Usually during development stage, an analytical subdomain model (ASM) is often preferred to be used in the design of electric machines since ASM has faster computational time compared to the finite element method. differential evolution algorithm is deployed to provide the optimization process in searching the optimal motor parameters iteratively and intelligently with specific objective functions. For this purpose, a three-phase, 6-slot/4-pole permanent magnet synchronous motor (PMSM) intended for the underwater propulsion system is first designed by using ASM and then later optimized by differential evolution algorithm. Five main motor parameters, i.e., magnet pole arc, magnet thickness, air gap length, slot opening, and stator inner radius are varied and optimized to achieve the design objective functions, i.e., high motor efficiency, high output torque, low total harmonic distortion (THDv) in back-emf, and low cogging torque. Results from differential evolution optimization show an improved performance of the proposed PMSM where the efficiency of the motor is increased to 96.1% from its initial value of 94.2%, 13% increase in the output torque, and 4.1% reduction for total harmonic distortion in its back-emf. Therefore, DEO can be highly considered during initial design stage to optimize the motor parameters in developing a good underwater propulsion motor.