Design And Optimization Of Permanent Magnet Vernier Machine For In-Wheel Drive Application

With the rapid growth of the world’s population and transportation demand,the global energy system and ecological environment are facing tremendous pressure.Electric vehicles have become a research hotspot in the automotive field due to their low pollution,zero emissions,high efficiency and many other advantages.In-wheel motor drive technology integrates power,transmission and braking devices inside the hub,simplifies the structure of the drive system,and will become an important development direction for electric vehicle research.Permanent magnet synchronous motors have the advantages of high power density and high efficiency,so they have become the first choice for wheel drive motors,but the friction loss and vibration noise caused by the mechanical deceleration mechanism also need to be solved urgently.Therefore,topologies of field modulation electric machines based on the principle of magnetic gears have been proposed successively.The permanent magnet vernier motor is one of the field modulation electric machines.It has the advantages of simple structure,high torque density and high reliability,so it has broad application prospects in the field of in-wheel motors.In this thesis,the consequent-pole,the rotor axial segmentation,the concentrated winding and the stator split tooth are combined,and a new type of field modulation permanent magnet vernier machine for in-wheel motor drive is proposed.The machine has the following characteristics: 1)It adopts the consequent-pole,in which part of the permanent magnets are replaced with iron cores,and can still ensure torque output capacity while saving the amount of permanent magnets;2)It adopts the rotor axial segmented structure.The rotor is staggered up and down by one pole angle,which significantly weakens the even harmonics of the back EMF and suppresses the torque ripple;3)The armature winding is in the form of fractional slot concentrated winding,which effectively reduces the mutual inductance between phases and the length of the winding ends,and improves the operating reliability and fault tolerance of the machine.Firstly,the technical background of the in-wheel motor and the current research status at home and abroad is introduced and the topology of the magnetic field modulation machine based on the principle of magnetic gears is discussed.Besides,the related research progress and hot issues of vernier machine are emphatically explained,and the research of motor optimization algorithm is mentioned.Secondly,the air-gap field modulation theory is introduced,and the operating mechanism and torque performance of the permanent magnet vernier motor are analyzed based on the magneto motive force(MMF)-permeance model.Combined with the consequent-pole and rotor axial segmentation,the topology of a new type of field modulation permanent magnet vernier machine is proposed,and its topology and working principle are described in detail,and a 2k W prototype is designed,including the design of rated parameters,main dimensions,pole/slot combination,armature windings,air gap,permanent magnets and the selection of materials,etc.In addition,in order to ensure the torque performance of the motor,the motor is optimized using algorithms.The design variables were selected through sensitivity analysis and the response surface model was used to establish a multi-objective optimization function.Combined with the adaptive genetic algorithm,the motor was globally optimized,and the optimization result was compared with the initial prototype’s,thus verifying the reliability of applying adaptive genetic algorithm to motor design.Finally,in order to ensure the stable and reliable operation of the motor,the loss and temperature rise of the machine is analyzed.A lumped parameter thermal network model was established according to the topology of the motor and the heat transfer mode,and the temperature rise of the machine under rated conditions was obtained through iterative calculations.Besides,JMAG is used to analyze the transient temperature rise of the motor and obtain the temperature cloud diagram of each part,which verifies the accuracy of the thermal network modeling method.