Design Of Brushless DC Motor For Electric Vehicle And Research On Cogging Torque Optimization

Because of environmental pollution and energy problems,development of electric vehicles in line with the trend.The performance of driving motor determines the reliability of electric vehicle operation.Electric vehicle drive motor needs to have high power density,fast climbing,high speed,high efficiency and wide speed range and other characteristics.Because the motor will produce the cogging torque in the working process,and then produce the vibration and noise,it is of great significance to the design of electric vehicle motor and the optimization of the cogging torque.Firstly,analyze the performance and characteristics of different types of drive motors,select the most suitable BLDC motor as the drive motor that is designed in this paper,and anslyze its structure and principle deeply.According to the performance index and technical requirements of BLDC,determine its rated performance technical index,including rated power,rated speed,rated voltage,etc;Summary the design method and process steps of the motor,according to the experience and basic physical formula,calculate the main size,electromagnetic and circuit relations,including the main structure of stator,winding,permanent magnet materials,the air gap length,electromagnetic load,flux and working efficiency to determine key parameters,complete the motor stucture optimization design.Secondly,analyze the obtained parameters by finite element method through Ansoft.Simulate the no-load characteristics of the motor in the transient magnetic field,mainly including no-load magnetic field,air-gap magnetic density curve,harmonic amplitude histogram,EMF and cogging torque waveforms,the waveforms are analyzed to verify the rationality of the designed motor.Because the cogging torque is too large,optimize the motor by changing its body structure.Analyze the effects of the dip depth,magnetizing mode and the deviation angle of magnetic pole group on the cogging torque.Analyze the other properties of the motor after changing a single parameter,including the EMF,air-gap magnetic density and magnetic force line.The results show that the reduction of cogging torque will affect other performance of the motor.Finally,in order to optimize the cogging torque better,propose and adopt RSM and PSO to optimize the parameters of the motor for the characteristics of strong nonlinear coupling,and build the mathematical model.Analyze the obtained variables by finite element method and compare the predicted value with the simulated value,and analyze the EMF.The results show that the cogging torque can be reduced better without affecting the EMF.