Study Of Asynchronous Motor Speed Sensorless Vector Control System For Electric Vehicles

Under the background of the energy crisis and the increasingly serious environmental pollution, electric vehicles especially the pure electric vehicles, as a new type of transport with high-performance, energy saving and environmental protection, has been raised more and more attention around the world. And the research on electric vehicles is gradually in depth. Motor is the power mechanism of the electric car. Asynchronous motor has simple structure, low cost, comparable to DC motor control performance when using the vector control technology, so it has been widely used in electric vehicles. But in order to obtain accurate motor speed signal, traditional asynchronous motor controller has to install speed sensors such as photoelectric encoder which will increase the system cost and complexity of hardware structure, and reduces the reliability. To overcome these shortcomings, the research and development of asynchronous motor speed sensorless vector control technology and its application for electric vehicles has become the focus of attention.After in-depth study on the basic principle of speed sensorless vector control, an asynchronous motor speed sensorless vector control system based on DSP (TMS320F2808) is designed. Through simulation and experimental test, the performance of control system has been evaluated. The speed sensorless vector control algorithm has been implemented to a designed low-voltage high-current squirrel-cage asynchronous motor. The whole system has been installed to a designed electrical vehicle which shows a well performance.First, the thesis introduces the development of electric vehicles. After comparing the advantages and disadvantages of different types of motors, the low-voltage squirrel-cage asynchronous motor is decided as the drive motor for electric vehicle. Then based on the analysis of asynchronous motor mathematical model, the principle of asynchronous motor speed sensorless vector control technology, the implements of SVPWM and flux observer are discussed in the thesis. A special flux observer combining of voltage model and current model is designed to realize an accurate observation in wider range of speed.The hardware and software design based on TI's TMS320F2808 is presented in the thesis. TMS320F2808 is a high-speed, low-cost, highly efficient DSP chip, which can fully meet the system requirements. Finally, the thesis presents the simulation using S-function to analyze the speed sensorless vector control method performance in the condition of no-load and load. A series of experiments verify the correctness and feasibility of system design.Simulation and experimental results show that the asynchronous motor speed sensorless vector control system proposed by the thesis is appropriate, and has good static and dynamic characteristics and stability.