Development Of Controller For Permanent Magnet Brushless DC Motor

We use rare-earth material as a material of brushless DC motor(BLDCM).BLDCM has the advantages of small size, high reliability, simple structure, convenient maintenance etc..Because brushless DC motor uses power electronic devices for commutation instead of mechanical commutation, so it has many advantages of DC brush motor such as high operating efficiency, good speed control performance and so on. In recent years, due to its excellent properities, brushless DC motor is widely used in many fields such as aerospace,automotive electronics, household appliances, fitness equipment, etc. Because the position sensors can not be used in harsh environments, so the reliability of the system will reduce, and position sensors will increase the cost and size of brushless DC motor. Since the late ‘90s sensorless control of brushless DC motor has been an important research direction in the industry.This paper firstly introduces the development situation and application prospect of permanent magnet brushless DC motor, then introduces the basic composition of Brushless DC motor system. On this basis, this paper analyzes the operation principle of the brushless DC motor. Then we establish related mathematical models. By the brushless DC motor control system model in Simulink, we do several simulations. The simulations provide a theoretical support for the follow-up works.Then, combined with a actual project during my studying for master degree, this paper introduces a control strategy of permanent magnet brushless DC motor, simple sine wave control by using the special control chip. In the simple sine wave control by using the special control chip, the chip's internal structure, functions of pins, and control principle are described in detail. After completing the design and debugging hardware circuits,we try to regulate lead angle with different loads. By using dynamometer system,we test and get the efficiencies of the motor's controller with different lead angles, thus we can select appropriate lead angle, in order to meet the project requirements. During the period of regulating the lead angle, we also encountered the situation that the lead angle is unable to adjust, this paper describes the situation in detail below, in order to provide references for related researchers.Combined with an actual protect, this paper introduces a square-wave driven sensorless control strategy of brushless DC motor. Then analyses system's composition and operation principle. This paper focuses on rotor position acquisition, "three-step" start-up and switching from start-up mode to closed loop mode,which are the three key technologies of the snesorless control. Based on the three key technologies, this paper describes the controller's hardware circuit structure and software control algorithm. Finally, after finishing the design of hardware and software, we make a sample BLDCM forexperiment. The experiment results verify the correctness of design. By comparing the experiment results with sensor control, we can get sensorless control's start-up capacity with a load and the efficiencies when running normally. At last, I make a summary of the full paper, point out the deficiencies of the paper, and outlook the work in the future.