Design And Research Of Pole-shaping Flux Modulation Permanent Magnet Motor

With the proposal of the national goal of "carbon peak carbon neutrality",electric vehicles have entered the fast track of development by virtue of their advantages of pollution-free and high-efficiency.With the success of commercialization,electric vehicles have gradually become one of the main transportation tools for people to travel today.As a key component of electric vehicle power output system,the performance of in-wheel drive motor directly affects the vehicle power performance.Flux modulation permanent magnet motor can meet the requirements of direct drive because of its low speed and high torque.In particular,the outer-rotor type flux modulation permanent magnet motor.Due to the outer-rotor structure,it has strong adaptability and obvious advantages in the field of direct drive in-wheel motor,so it has a wide range of development prospects.Based on the principle of air-gap magnetic field modulation,this paper takes a Pole-shaping-modulated permanent magnet in wheel motor as the research object.This paper proposes a design and optimization method of flux modulation permanent magnet motor based on multi-harmonics of the air-gap,and systematically carries out relevant research and exploration on the torque performance of the motor,specifically summarized as follows:(1)Firstly,the research background and significance of electric vehicles are introduced,and the development history of in-wheel motor and the research status of flux modulation permanent magnet motor are expounded.On this basis,the theoretical relationship between the air-gap flux density harmonics and the output torque of the motor is analyzed and explored from the perspective of the generating mechanism of the air-gap magnetic field of the field modulated motor.At the same time,the internal relation between air-gap flux density harmonics,output torque and torque ripple is further deduced.Based on the above analysis and derivation,a design and optimization method of flux modulation permanent magnet motor based on airgap multi-harmonics is proposed,and a PSM-PM in wheel motor is selected as the research object to carry out detailed work.(2)Based on the analysis of air-gap multi-harmonics,air-gap multi-harmonics are taken as the intermediate variable between permanent magnet field,armature field design and motor performance.Then,from the perspective of the three elements of the motor,aiming at the permanent magnetic field and armature magnetic field,the pole-arc cutting and the multi-harmonic design of star-delta winding are completed respectively.After that,the output torque and torque ripple before and after the multiharmonics design are compared and analyzed.(3)On the basis of the same analysis of air-gap multi-harmonics,air-gap multiharmonics are taken as design variables and optimization objectives of the motor at the same time,so as to establish an internal relationship between air-gap multiharmonics,parameter variables and motor performance objectives.In order to optimize the design process,the output torque harmonics and torque ripple harmonics were selected based on the flux density amplitude,and the importance of some specific air-gap harmonics to the motor torque performance was determined.At the same time,sensitivity analysis method is used to evaluate the sensitivity between airgap harmonics and torque performance of motor.Here,the air-gap harmonics are not only the design variable of the motor,but also the multi-harmonics which are important to the torque performance are determined by the standard of amplitude.Airgap harmonics are also optimized objects.The key parameter variables that are important to air-gap harmonics are obtained through sensitivity analysis.(4)After that,the response surface optimization method is used to optimize the above key parameter variables,and the optimal parameter variable combination was selected.After the optimization work is completed,the model before and after the optimization of the motor simulation and comparative analysis of the performance,including the motor magnetic field distribution,no-load inductance,cogging torque,output torque,torque ripple...(5)Finally,a PSM-PM in wheel prototype was manufactured according to the optimal parameter model,and the test bench was built.Then,experiments on the prototype including no-load inductance,steady-state characteristics and dynamic response characteristics were carried out on the platform,and the experimental data are analyzed.The results show that the experimental data are in good agreement with the simulation results,which verifies the correctness and feasibility of the proposed motor torque performance improvement method based on the multi-harmonics of the air-gap.Combined with the above research,it is shown that PSM-PM in wheel motor has a good application potential in the field of electric vehicle in-wheel motor.