Design Optimization Of A Novel Direct Drive Halbach Array Permanent Motor For Electric Rudder

Halbach array is a permanent magnet array with superior magnetic properties.Its good magnetization effect and sinusoidal magnetic field are very suitable for improving the electromagnetic performance of permanent magnet synchronous motor used for electric rudder.This paper takes aim at permanent magnet synchronous motors used for electric rudder with high torque density and low torque ripple.A new Halbach array is proposed to reduce motor effective mass and torque ripple and it is applied to direct drive permanent motor.The magnetization effect and harmonic distortion rate of the new Halbach array are studied by analytical method.The initial motor stator,rotor and the new Halbach array structure are optimized based on differential evolution algorithm.Effective mass and torque ripple of the motor before and after optimization are compared.The research content of this paper is mainly composed of the following aspects:1.This paper proposes a new Halbach array and establishes the analytical model of noload magnetic field of the new Halbach array stator slotless permanent magnet synchronous motor,The expression of residual magnetization of the new Halbach array is deduced and the no-load air gap magnetic field of the stator slotless permanent magnet synchronous motor is calculated according to the magnetic field analytical theory.2.The stator slotted model is transformed into a slotless model by conformal transformation.Complex air-gap permeability is calculated.And the no-load air-gap magnetic field of the new Halbach array permanent magnet synchronous motor is analytically calculated.The correctness of the analytical method is verified by finite element method.On this basis,the influence of structural variables on the performance of the new Halbach array is studied.And A hierarchical analytical optimization method is proposed to study the multivariable optimal design of this Halbach array.3.According to the design index of the rudder motor,this paper preliminary designs a direct-drive permanent magnet motor for electric rudder and the new Halbach array with four permanent magnet per pole is applied to this design,then establishs the parameterized finite element model.Based on finite element method,The magnetic field distribution,back emf of phase,cogging torque and torque ripple is analyzed.4.Based on the preliminary design of direct-drive permanent magnet motor for electric rudder,an optimization model is established.This paper combines with finite element software and optimization software to optimize this motor based on differential evolution algorithm.Effective mass and torque ripple of the motor before and after optimization are compared.