Study On BLDCM Sensorless Control System

Brushless DC motor(BLDCM) is a kind of electromechanical integration machinery, and its technique has been rapidly developed in recent years with the appearance of new type of permanent magnet materials and the help of the development of power electronic technique.It is electronic instead of mechanical brushes and commutator to achieve the DC motor commutation,not only reduces the cost of the motor,and increased system reliability,and further enhance the scope of application of the motor,so sensorless control of brushless DC motor control technology to become a hot research field.Firstly the paper reviews the development process of brushless DC motor, status and technology.Then,the thesis describes the composition of brushless DC motor structure,basic operation principle,running characteristic of BLDCM.Also motor rotor position detection under sensorless controlling is studied and the advantage and disadvantage of various kinds of position signal detection method are analyzed. Especially further analyze is made on the perational principle of zero-based rotor position detection method and also the control system hardware and software to detailed analysis of program design,while the hardware and software interference analysis and presenting the methods to eliminate these disturbances.This paper adopts "the three-step"motor starting technique which including the "rotor pre-setting", "accelerating" and "state-changing" step is discussed generally.And a sensorless BLDCM system is designed with the TMS320F2812 as microprocessor,giving practical EMF zero-crossing detection circuit,power driver circuit,current and voltage detection circuit and over current protection circuit.the reason of rotor position error in the zero-crossing of BEMF sensing method is analyzed, and the compensation methods are also given in the software design.Finally,The results of the experiment achieve the motor's correct commutation and smooth running and show that the sensorless brushless DC motor control system can make the motor.start successfully proved the correctness and effectiveness of system design.