Study On Sensorless Control Of Brushless DC Motor

Brushless DC Motor(BLDCM) is the new integration mechatronics motor, with more and more focus on its technology characteristic and practical application. It has also become the development tendency of the small and special electrical machinery. Brushless DC motor is widely used in the household appliances, the computer auxiliary equipments, the acoustic image equipments, the office automatic equipments, the electric vehicles and the industry control in detail. We can estimate that, it will be used in more fields along with the unceasing progress of brushless DC motor and its control technology.Firstly the background, development and future prospect of BLDCM is described in detail. Then, the thesis introduces the composing parts, basic operation principle, running characteristic and transfer function of BLDCM. Also motor rotor position detection under sensor less 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 operational principle of a new rotor position detection method on back-electromotive force(Back EMF).This paper focuses on the whole digital sensorless control system of BLDCM based on singlechip. According to the demand of the project,the single chip—ATmega8 of the company of ATMEL is chosen as the control chip of the motor drive. Recurring to the chip strong disposal ability and abundant peripheral equipments, the whole system leaves out complicating hardware circuits and improved the credibility system.For the hardware part, the design of several chief circuits is expounded. For the software part, with the introduction of modulization design concept, some procedure flow charts of main program subroutine are offered and several problems of software realization are investigated.At last, the testing phenomenon when the control system running is observed and the experimental results are analyzed. The experiment results verify the correctness and validity of this sensorless control system of BLDCM.