| In recent years, Brushless Direct Current Motor is widely used in the field of motor control because of its characteristics of energy saving, low noise, compact structure, and long service life. Currently, most of motor applications are driven by brushed motor or brushless motor with sensors. However, the brushed motor not only requires periodic maintenance but also generates noise causing EMI, and its efficiency is lower than brushless motor. While the brushless motor increases cost and reduces the system reliability because of the position sensor. Therefore, it’s of great significance to use a sensorless BLDCM in some motor applications.The main purpose of this thesis is to design and implement a sensorless BLDCM control system. The hardware and software of this system are designed based on STM32F051, and the estimating rotor position method is based on back-EMF zero crossing detection. This paper presents two main improvements:a "preposition-two-acceleration" method is implemented in order to avoid starting failure; the capacitors in traditional rotor position detecting circuit are removed in order to run at a high speed. At the end of this paper, the main signals of the controller, such as voltage, current, were analyzed. The results show that the control system meets the design indexes. It starts smoothly especially when the motor has more than 8 magnetic poles. Its electrical rotating speed can be up to 210,000 rpm. It has the function of constant-speed control and constant-current control. The supply of this controller ranges from 9V to 12V and the maximum current can be reach at 20 A. Besides, it also has a function of low voltage protection and thermal protection. And it has passed a 2000 hours aging test.The control system is suitable for the hand-held vacuum cleaners application. Besides, it is also suitable for some applications such as model aircraft, electric fan and other similar applications. |
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