Research On Position Sensorless Control Of Brushless DC Motor In Electric Vehicle

Traditional fuel vehicles not only consume fossil energy,but also emit a large amount of exhaust gas,which has a serious impact on the world energy crisis and air pollution.Pure electric vehicles have developed rapidly in recent years.As a preferred solution for future travel,they have the advantages of no pollution,low noise and high intelligence.The electric motor drive system of electric vehicles is the heart of electric vehicles.Its performance directly affects the driving experience of passengers.It is necessary to conduct in-depth research on it,and the drive control without position sensor can adapt electric vehicles to more complex environments.Reduces motor weight and reduces costs because no sensors need to be installed.This paper designs a brushless DC motor position sensorless drive control system based on STM32 chip.The system has precise control,fast speed response and high stability.This paper first studies through theoretical research,and fully understands the performance requirements of electric vehicles for electric drive systems,and analyzes the mathematical model and control principle of electric vehicles.In this paper,the PID control algorithm is studied.According to the integral saturation phenomenon of the integral term in the algorithm,the integral parameter optimization based on the variable integral idea is proposed,which realizes the function of integral accumulative acceleration changing with deviation.For the complicated problem of PID parameter setting,this paper proposes to use the hill climbing algorithm to quickly adjust the parameters on the Simulink simulation platform.The obtained PI parameters have important reference value.When everything is ready,start designing the hardware and software for the control system.Using STM32F051R8T6 as the control chip,a software and hardware system can be built to realize position sensorless drive control.And the incremental PID algorithm is improved,which can effectively suppress the overspeed of the speed loop.Furthermore,by detecting the current value of the current-sense resistor at thestart of the motor to determine the initial position of the motor rotor,the speed pulsation at the start of the motor can be effectively alleviated,thereby achieving a more smooth start.This paper builds an experimental platform to perform performance tests on the designed control system,including PWM wave detection,motor start test and closed loop test.The test results show that the position sensorless control system of the brushless DC motor for electric vehicles designed in this paper runs stably.According to the relationship between the rotor magnet and the armature reaction,the“three-stage” starting method can be optimized to make the motor start more stable.The optimization design of the incremental PID control algorithm based on variable integral can effectively suppress the generation of overshoot in the speed regulation;the design of the motor control drive system meets the expected requirements.