Study On The Control Of Sensorless Brushless DC Motor And Application

The automotive electronic fuel pump is one of the core components in automobile fuel supply system, which's main role is to provide fuel with sufficient pressure and flow for the fuel supply system. Contrasted with DC motor, sensorless BLDCM(brushless DC motor) has no mechanical commutation components, which has several advantages such as low working noise, no commutation spark and better adaptability for different fuel, etc. So, its application in the automotive electronic fuel pump would greatly reduce failure rate and increase lifespan. Therefore the studies about the key technologies of BLDCM and its application in the automotive electronic fuel pump have an important practical significance.In this thesis, the key technologies of the sensorless BLDCM control system are deeply analyzed, including the rotor position detecting method, the starting algorithm, control algorithm, etc. Combining with the high reliability and low cost demand of automobile electronic fuel pump and after analyzing the problems of conventional BEMF(back electromotive force) zero-crossing rotor position detecting method, the digital filter based on majority function is designed and applied, which would reduce costs as well as increase reliabilities. The principles of choosing PWM mode and frequency are given through theoretical analysis. In the process of motor starting, three-step starting algorithm method is applied. Aiming to solve the problems about matching launch parameters in the algorithm, the ideal parameters are acquired through theoretical calculation by comparing with DC motor, which can obviously improve reliability. Considering the complex working environment of electronic fuel pump, the fuzzy PID controller is designed and applied, which would acquire better effect.The experimental results of a BLDCM show that the ideal launch parameters could make commutation steadier and launch time shorter. The digital filter based on majority function could overcome the problems of conventional BEMF zero-crossing rotor position detecting method, adapt lower range of speed and acquire better performance of rotor position detecting. The fuzzy PID controller could make the control system get better transient and steady state performance. They all validate the reliability of hardware and software design of the system. Finally a test platform is built to simulate the actual working conditions of the automotive electronic fuel pump. The experimental results show that the design of sensorless BLDCM control system can meet the application requirements of automobile electronic fuel pump.