Design Of Motor Speed Control System For Power-assist Electric Bicycle

With green travel and health travel concept gradually deepened in society and the relevant provisions of the state further improved and standardized,electric bicycle has great potential and broad market in China.and the related research of the electric vehicle will become popular within a period of time.However,there are a number of electric bicycle in the market with variety of obvious design defects at this stage: vehicle quality standard,too simple control strategy,speed control with open loop,etc..this paper,based on the practical background of the electric vehicle,focusing on the motor drive and control algorithm design,mainly completed the following work:First introduces the brushless DC motor(BLDCM)structure and working principle,put forward the selection scheme of wheel motor vehicle system;discuss the requirements of motor control,the torque as the control object to achieve closed-loop control,and at the same time based on vehicle dynamics model,the optimal output torque value is discussed;for the Sensorless Brushless DC motor selected,the back EMF method of rotor position detection is rised,the algorithm complexity instead of hardware complexity to reduce the cost is proposed to improve the stability of the system.Second,the circuit design scheme and chip selecting strategy of motor control is disscussed,and made a detailed introduction to the motor control and drive circuit design;As the torque control algorithm,the vector control method of BLDCM motion decoupling is rised,to simplify the calculation;in the modulation of the driving voltage,the voltage space vector(SVPWM)algorithm is proposed to improve the control accuracy,as while as to improve the power source efficiency.The torque closed-loop PI controller control system is used in the vehicle based on the control strategy,then introduces the PI controller parameter tuning method to improve the system control accuracy and response speed of the moped.In the end,Based on the research objective and control the requirements,set up a hardware and software experimental platform of electric vehicle project,and complete the circuit testing and algorithm verification on the platform.It’s can be seen from the experiment results that the torque closed-loop motor control system designed in this paper can initially meet the steady and dynamic requirements of the electric vehicle project,at the same time it proves that the system has certain stability in the normal driving(not over-speed and in normal resistance).