Research On Wheel Side Direct Drive External Rotor Motor For Pure Electric Vehicle

The structure of permanent magnet wheel edge straight driving force assembly is obviously superior to the centralized driving structure in terms of high transmission efficiency and effective reduction of vehicle space occupation.Compared with the traditional inner rotor PMSM,the outer rotor PMSM has higher power density and torque density.This subject has studied the wheel-side direct drive motor of electric vehicle.In view of the special needs of wheel-edge direct drive motor,this paper has taken the design and optimization of wheel-edge direct drive motor as the main line,and studied the motor control,and finally calculated whether the temperature meet the requirements.In this paper,from the perspective of vehicle dynamic characteristics,according to the requirements of the dynamic characteristics of the wheel-side drive pure electric vehicle,the motor performance parameters are checked to determine the performance parameters of the motor.Firstly,the pole slot matching and rotor magnetic circuit structure of the motor are selected reasonably.Next,the main size of the motor,stator tooth and yoke magnetic density,electromagnetic load,no-load counter potential and other basic parameters of the motor are calculated by the motor magnetic circuit algorithm.After the initial scheme has been determined,finite element software is used to simulate the rated working condition,overload working condition and weak magnetic working condition of the motor.For the wheel-side direct drive motor,the vibration of the motor will have a great impact on the safety and comfort of the vehicle,of which the motor torque ripple is an important source of motor vibration,so this paper has adopted the method of uneven air gap to reduce the motor cogging torque and torque ripple.In the end,the efficiency distribution of the motor in the whole operating range is analyzed.For the pure electric vehicle,the motor control stragety has a very important impact on the motor operation,With the edge of direct-drive permanent magnet motor control strategy were analyzed,and designed a sliding mode speed controller,compared to the traditional PI speed controller,the control precision and response speed of the whole system,structures,the vector control model of the permanent magnet motor,the simulation of the motor speed,torque,current waveform,verify the feasibility of control model.Since the wheel-side direct drive motor runs for a long time in rated working conditions,the motor output peak torque,the motor current is large,and the thermal load and copper consumption of the motor are high in overload working conditions,so the motor runs at a high temperature in these two working conditions.In order to check whether the temperature rise of permanent magnet motor can meet the requirement of insulation material,the temperature field simulation model of permanent magnet motor is established.The motor temperature distribution under rated and overload conditions has been calculated to verify the safe operation of the motor.