Research On Torque Ripple Suppression Technology Of Brushless DC Motor For Electric Vehicle

Brushless DC motor is widely used in the field of electric drive because of its simple structure,small size,light weight,large output torque and other advantages.However,due to the structural characteristics of Brushless DC motor,it has obvious torque ripple in operation.When it is applied in the field of electric vehicle drive,the vibration and noise problems brought by brushless DC motor bring bad experience to people.Therefore,this topic studies the torque ripple suppression technology of Brushless DC motor for electric vehicles,so as to achieve the control effect of low torque ripple.The main contents of this paper are as follows(1)This paper studies the causes of various types of torque ripple of Brushless DC motor for electric vehicles,as well as the development status of torque ripple suppression technology at home and abroad,analyzes and compares the torque ripple suppression effect of common control strategies for brushless DC motor,and analyzes the requirements of the control system of Brushless DC motor for electric vehicles,The principle and problems of traditional direct torque control strategy are studied.(2)Aiming at the problem of commutation torque ripple caused by the inconsistency of on-phase and off-phase current conversion rate during commutation in traditional direct torque control(DTC),an improved DTC control strategy based on optimized current prediction model is proposed to suppress the phase current fluctuation during commutation and then the commutation torque ripple of motor.At the same time,combined with the optimized back EMF sliding mode observer based on arctangent function and fuzzy adaptive controller,the closedloop of electromagnetic torque and speed in the traditional direct torque control is improved,and the stability and robustness of the control system are improved.(3)Aiming at the problem of torque ripple in non commutation region caused by traditional modulation method in regenerative braking of electric vehicle,a new method based on PWM is proposed?OFF?PWM is a new modulation method.In this method,the non commutation section is subdivided into 30 degree sectors to avoid the extra loss caused by the non conducting phase participating in the dynamic freewheeling process.In each sector,the appropriate switch tube is selected to modulate and control the winding current conduction path to form a boost chopper circuit for feedback braking.At the same time,the non commutation torque ripple caused by the non commutation dynamic freewheeling is avoided.(4)Complete the hardware and software design of Brushless DC motor controller for electric vehicle,build and test the motor experimental platform.According to the requirements of Brushless DC motor control system for electric vehicles,the overall control scheme is designed,including the hardware part of each module circuit,combined with the improved direct torque control algorithm of optimized current prediction model,the control software is written.In order to achieve low torque ripple control in a wide range of speed and load changes,the motor was tested under different speed and load conditions on the experimental platform.