| The main purpose of this paper is to study high quality control of the sensorless brushless DC motor (BLDCM). On the base of roundly analyzing and studying the running mode of the sensorless BLDCM, we explain theories and realizable methods of detecting back electromotive force, phase verdict and phase compensation in detail. In order to improve the timing performance, the control strategy of this system is to use digital speed closed-loop control. The control system adopts high capability singlechip, ADuC812 (8052-compatible core). It can expediently achieve A/D (12bit), D/A (12bit), phase compensation of the rotor position singles, and speed closed-loop control , and fully resolves the well-off switch from the out-synchronization to the in-synchronization.The practical prototype of the system is developed for the control of a dentist' sensorless brushless DC drill motor. It can be seen from experimental results, that the BLDCM control system reaches all the qualities required by the drill motor. The motor starts fast and operates stably in a very small torque ripple. At the same time, the system is simple, widely adaptive, and reliable. Moreover, it can be used in other fields such as air conditioner. |
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