| The electric vehicle has the advantages of high efficiency energy saving and little pollution, people is paying more and more attention now. In this paper, the design and production of low-speed electric vehicle drive motor project as the background, the research is focus on the development of efficient, stable electric vehicle drive motor and its control system. Use a miniature low-speed electric vehicle as a platform, discuss and analyze the dynamic performance requirements, and choose the matching motor. Take All the operating characteristics and control characteristics of the drive motor into concern, brushless DC motor is selected as drive motor。And design a brushless DC motor control system based on the high performance digital signal controller. Discuss the installation error of HALL sensor effect on motor performance, and point out the weakness of the traditional three segment operation mode, put forward the suitable brushless DC sensorless control scheme for low-speed electric vehicle.This paper first analyzes the body of Brushless DC motor, and establishes a three-phase star connected motor mathematical model. Discuss the work principle and speed control performance of permanent magnet brushless DC motor, and it can change the stator winding average voltage to change the motor speed result from the discussion, and provide a theoretical basis for the use of PWM. Then it introduces the principle of the brushless DC motor sensorless control and rotor position signal detection method.Analyze the given dynamic performance demand for low-speed electric car normal driving. The physical parameters of electric vehicle driving and climbing is derived by the resistance, and then convert parameters to the motor, obtain the motor rated output power and speed, determine the selection scheme of motor. The control object is selected, the performance requirements of motor control system, this control system functional requirements and overall design scheme of the control system. Finally, put forward a kind of suitable startup scheme for low-speed electric vehicle brushless DC motor sensorless, it combines the counter electromotive force detection method with inductive method, and it effectively avoids the starting torque vibration brings by the traditional start scheme.Design the hardware circuit of the system based on the performance requirements of Brushless DC motor and control system, and put forward the hardware design of the system overall structure. Use the microchip company’s dsPIC33FJ32MC204 as the main control chip, peripheral rich system resources and can meet the requirement of control system. At the same time with different system module power supply, power supply circuit is designed for different levels. Then design the back EMF Detection circuit, system power circuit, power driver circuit, current and voltage detection circuit, protection circuit and alarm circuit etc. provide the analysis of circuit diagram.On the basis of the hardware circuit, the system establishes software platform, system software’s main function is to achieve the motor control, system protection, and motor function. Put forward the overall framework and structure using modular design method. Each sub task is using the method of time-sharing scheduling system for the allocation of resources, maximize system utilization. Mainly introduce the flow chart of the main program, timer interrupt, fault protection, signal acquisition, control mode switching procedures. Switch the position sensor and position sensor mode of brushless DC motor control system to ensure the motor in the stationary stage of high speed operation and comfort. It has some application value.Match the selected motor, the controller and the experimental platform, then test the data of no-load and load speed, climbing ability, no-load and load current, vehicle speed, load and load when the motor temperature rise, the temperature rise data controller. The experimental waveforms and the solutions of the problems encountered are given. By the waveform analysis and the actual test data can be seen, the motor and the controller can meet the requirements of low speed operation of the electric vehicle. The new control method can be applied suitably, and improve the performance of the low-speed electric vehicles.Finally, summarize the paper. The performance of the design is good and the practical application is conducive to the promotion of electric vehicles market. At the same time, in view of the problems encountered during the work, discuss the improvement scheme and make an expectation for the future work.In this paper, select of the brushless DC motor and design its control system, put forward a kind of inductive method of Sensorless Brushless DC motor control scheme. Improve the algorithm in the process to make the operation efficiency and stability, the designed system has programmable ability and powerful system protection, it is able to adapt to the electric vehicle operation in the harsh environment. So it has high reliability and certain application value. |
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