Research On Axial Flux Permanent Magnet Machine For Electric Vehicle

Compared with the traditional radial flux permanent magnet motor,axial flux permanent magnet motor has higher power density and more compact space structure,which has attracted more and more attention.It has important research and application value in the field of drive system of electric vehicles.In this paper,the electric vehicle is used as applications.The topology,electromagnetic design method and key optimization technology of axial flux permanent magnet motor are studied,and the effective methods are proposed.The main contents are as follows:In this paper,a variety of topological structures of axial flux permanent magnet motor are studied.The characteristics of different topological structures and basic magnetic circuit flow direction are introduced.The structure,material and performance characteristics of stator and rotor are analyzed.Finally,the characteristics of the yokeless and segmented armature(YASA)axial flux permanent magnet motor is introduced,and the advantages of this topology are described.From the perspective of dynamic performance of electric vehicles,based on the idea of global matching design,considering the operation requirements of electric vehicles under various conditions,the parameter matching method of motor is studied.Based on design experience and the general design method of axial flux motor,the electromagnetic scheme of the motor is preliminarily determined.The main size calculation,stator design,permanent magnet design,slots and poles combination selection,winding design and material selection are carried out.The no-load characteristics,torque characteristics,loss characteristics and overload capacity of the designed YASA motor are analyzed by finite element method.As the drive motor of electric vehicle,the quality of output torque is worthy of attention.Aiming at the problem of excessive cogging torque in axial flux permanent magnet motor,a cogging torque suppression method based on H-type magnet is proposed.Firstly,the influence factors of cogging torque are analyzed theoretically.The influence of pole-arc coefficient on the amplitude and phase of cogging torque is studied,and the optimization mechanism of the proposed H-type magnet method is clarified.Then,the cogging torque reduction effect of this method is studied by using finite element analysis and taking an axial flux motor as the optimization object.Aiming at the problems of low efficiency and poor optimization effect of traditional multiobjective optimization methods,a multi-objective optimization method is proposed,which combines sensitivity analysis,back propagation(BP)neural network algorithm and multiobjective genetic algorithm(NSGA-II).At the same time,the H-type magnet cogging torque suppression method proposed before is applied.Two parameters of H-type magnet and some other motor structure parameters are selected as the parameters to be optimized,and the average torque and torque ripple are taken as the optimization objectives.Multi-objective optimization of YASA axial flux permanent magnet motor initially designed in this article is carried out.And the optimized motor structure parameters obtained by the previous multi-objective optimization method are verified by finite element calculation.