Design And Analysis Of Permanent Magnet Vernier Machine For In-wheel Traction Application

The in-wheel direct-drive system of electric vehicle eliminates the traditional gearbox and other mechanical transmission device,therefore,it can reduce the volume of drive system and the weight of the electric vehicle.In addition,the in-wheel directdrive system can also improve the dynamic response of drive control and performance of electric vehicle.However,in the in-wheel direct-drive system,the drive machine must meet the strict requirtment in terms of the high output troque density,high efficiency and high power density demand.Thus,in the thesis,research work focused on the design of in-wheel direct drive machine for electric vehicles is carried out,which can be summarized as below:1.The structure and working principle of the electric vehicle drive system are expounded.Combined with the requirements of the electric vehicle's dynamic performance,the selection method for the main parameters of the electric drive machine drive system are analyzed.The main parameters of a four-wheel direct-drive hub machine that meet the requirements are calculated for a small electric vehicle.2.Based on the flux modulation principle,the split-teeth permanent magnet vernier machine has the merits in terms of simple structure,high torque density and short end winding.The key factors such as winding arrangment,pole-slot combination and flux modulation ratio of this kind of machine are analyzed and compared.The temperature field calibration of the proposed machine is analyzed;the advantages and disadvantages of the permanent magnet vernier machine and the permanent magnet synchronous machine as the hub drive machine under the same power conditions are compared.3.A permanent magnet Vernier machine with a V-type permanent magnet rotor structure is proposed.By optimizing the rotor structure,the torque density of the machine under the same rare-earth permanent magnet usage is improved,and also under the same torque output requirement,the amount of rare-earth permanent magnet is saved.The equivalent magnetic network method is used to analyze the permanent magnet vernier machine with V-type permanent magnet rotor structure.4.The machine overhang structure is introduced into the split-teeth permanent magnet vernier machine.It can improve the torque by 26.4% and the torque density of the proposed machine is 21.6Nm/L.Both finite element method and experimental test verify the effectiveness of the machine overhang structure.