| As a kind of green vehicle,EV(electric vehicle)has been paid more and more attention by people.In the development of EV,motor control technology is one of the key technologies,and it is also the most important problem to be solved in the research and development of EV.Permanent magnet brushless DC(direct current)motor has a series of advantages,such as high speed performance,high efficiency and simple structure,which becomes the mainstream of the field on EV drive motor.In this paper,the control system of brushless DC motor used in electric vehicle is studied.This paper first introduces the current research and development of electric vehicles.The driving motors of several EV are compared,which fully shows that the permanent magnet brushless DC motor drive motor is a promising electric car better.Then the paper takes the three-phase brushless DC motor as the carrier,analyzes some problems of the current permanent magnet brushless DC motor control system.Then the working principle and mathematical model of permanent magnet brushless DC motor is introduced in detail,and the direct torque principle of brushless DC motor is discussed,and the simulation and experiment are carried out.However,the traditional direct torque control has the disadvantage that the switching frequency is not fixed,and then analyzes the relationship between switching frequency and torque hysteresis,and proposes a new type of direct torque control.Energy recycling is an important requirement for motor application on electric vehicles,this paper proposes a novel modulation strategy—PWM_OFF_PWM,which can realize the energy recovery and inhibit continuous flow phenomena of non-conducting in the brake situation.According to the simulation analysis,the paper builds the hardware platform of the brushless DC motor control system based on the main control chip of DSP&CPLD,and introduces the hardware circuit and software design flow of DSP and CPLD,and the experiment debugging is carried out.The experimental results show that the new direct torque control system can effectively restrain the torque ripple and reduce the switching frequency and so on. |
