Research On Servo Drive System Of Permanent Magnet Synchronous Motor For Pure Electric Vehicles

As the core component of the pure electric vehicle,the motor control system directly affects the comfort and safety of the vehicle.Pure electric vehicles in China started late,which led to the production of motor control system in China is not perfect.At present,the brushless DC motor control system is widely used to control DC brushless motor,which scheme is simple and efficient,but the torque ripple is large,unable deceleration braking,braking,positioning,and gradually cannot meet the needs of the development of pure electric vehicles.In this paper,a set of high precision pure electric vehicle permanent magnet synchronous motor servo drive system is designed.Compared to the current brushless DC motor control system used in pure electric vehicles,the advantages of this paper are as follows: Constant torque,smooth operation,small jitter and mechanical noise;Precise control of position,which greatly reduces the overshoot caused by the process of parking and collision;The motor itself can be slowed down,which makes the deceleration of the car does not depend entirely on the driver to operate the mechanical brake;When the motor is at rest,there is a stationary magnetic field to prevent rotor movement,avoid the occurrence of slippery downhill parking;Powerful processing ability,can complete the motion control,feedback correction,error alarm,etc,which make the system only need one instruction to realize the precise control,and reduce the operation difficulty;The car running in the potholes,load fluctuation,the system can adjust the torque and increase ride comfort and to reduce the risk of losing control,placing obstacles or collision causes the load changes dramatically when braking,braking system can make corresponding processing.In order to make a detailed study on the control system of the pure electric vehicle motor,the torque control model is established in the d-q rotating coordinate system based on the Clarke and Park coordinate transformation.Using the Id=0 vector control strategy establishes a complete set of torque,speed,position control of the three closed loop servo control system,on which basis,the MATLAB simulation model is built,and the simulation results are analyzed.In order to apply the theory to practice,this paper designs a DSP and FPGA dual core as the core of the driver.Using Freescale DSP chip as the control core,responsible for the overall control and transaction management;The FPGA is used as the slave controller to complete the motor vector control algorithm,the space vector pulse width modulation(SVPWM)algorithm and the A/D sampling control current.The RS232 and RS485 communication functions are added,which makes it possible to observe and modify the operating parameters of the driver on the host computer;The communication interface of CAN bus is designed,which is suitable for the information exchange in the field of automobile.Through the MATLAB simulation experiment and the physical bench test,the system can meet the design requirements of the pure electric vehicle drive motor control system,which has reliable static stability,good dynamic response,smooth torque output characteristics.Under low load,speed control accuracy is ±0.04% and position control accuracy is ±1Pulse.