Study On Steering System Of Permanent Magnet Motor Wheeled Direct Drive Electric Vehicle

Electric vehicles have many limit conditions,and the wheel direct drive system because the motor directly connected to the wheel requires the motor cannot have large torque ripple.Permanent magnet motors meet this condition,so permanent magnet motors can be used on a large scale in electric vehicles.It is also a drive motor that is currently being developed by the world's mainstream car makers.Traditional vehicles use mechanical differentials to achieve a difference in speed between two wheels.Two wheels travel through different distances in a unit of time to achieve steering.This implementation method has complex mechanical structures and large losses affect the efficiency of the use of electric vehicles.The mechanical differential method is not suitable for the electric vehicle steering demand.Electric vehicle is driven by a motor,and the driving motor is directly connected with the wheels so that the electronic differential is born.The electronic differential cancels various mechanical structures and uses electronically controlled methods to achieve steering.According to the parameters of the modified vehicle model,the design of the permanent magnet motor for electric vehicles was carried out,and use Maxwell to simulate the designed motor.Due to the size of the motor of the electric vehicle is particularly strict,the thermal load of the motor will increase a lot as the size of the motor decreases.Therefore,thermal analysis and fluid analysis are indispensable components of the design of the electric motor drive motor.Using CFD simulation software to do fluid analysis to determine whether the overall temperature rise of the motor meets the requirements.Finally,prototypes were made and tested.Due to the steering system of the electric vehicle is achieved through the control of the motor,the control strategy of the permanent magnet motor is analyzed.The traditional PI control is improved,the control parameters are reduced,the precision of the control is improved,and using Simulink built a vector control model for permanent magnet motors for electric vehicles.In order to realize the electronic differential system of the electric vehicle,the permanent magnet motor and the traditional mechanical differential steering method were analyzed,and self-adaptive torque balance control scheme based on two permanent magnet motors as the driving motor was proposed.In view of the problem that the existing electronic differential scheme cannot effectively control the road under complicated conditions,this paper gives a solution based on the traditional mechanical differential and finally determines the control strategy of the electronic differential.Through the modification of traditional SUV models,the accelerator and brake pedals are retained,and the steering system and power system are modified.Two independent permanent magnet motors directly drive the power;the electronic differential is used in the steering to replace the traditional mechanical differential.Using Simulink and Carsim for joint simulation,obtaining a series of curves.Finally,driving was performed on a vehicle to test whether the electronic differential system was effective.It was verified that the designed electronic differential system was feasible.