The Research On Start Technology Of Brushless DC Motor Without Hall Sensor

The permanent magnet motor with rare earth materials is increasingly used in a variety of transmission system, which has the merit of small size, simple structure, high reliability, high efficiency etc. The sensorless brushless DC motor reducing the installation of a position sensor, has improved the reliability of the brushless DC motor applications, broadened the applications of the brushless DC motor, and reduce system cost at the same time. But, the start technology of sensorless brushless DC motor is still a technical difficulty. Currently, the prevalent software algorithms used are more complex, the hardware circuit has a high cost, motor parameter and environmental changes impact s the startup performance. With these shortcomings, design a low-cost and high reliability start method is necessary.Firstly, this paper introduces the development and application prospects of the brushless DC motor, and further introduces the status of a brushless DC motor control technology combined application. Then the body structure and working principle of the brushless DC motor are analyzed. On this basis, a mathematical model of the brushless DC motor and simulation system based on Matlab/Simulink is established.Next, the article describes research focus of the current sensorless brushless DC motor control technology and start technology, introduces sensorless control and motor starting principle of the back EMF(electro motive force) zero crossing detection method. On this basis, the overall design of sensorless brushless DC motor control system in this article is presented, the core control circuit based on TMS320F2812, the signal conditioning circuit, the power driver circuit, the peripheral control of the keyboard and the auxiliary switching power supply circuit are designed. At the same time, the circuit of traditional back EMF zero crossing detection is improved, so that the scope of application of the back EMF detection is improving.Based on analyzing the advantages and disadvantages of the traditional three-stage start method and other start-control mode, a new compound start control method based on the rotor pulse positioning and the back EMF zero crossing detection is presented in this paper. And specific implementation is also given.Finally, brushless DC motor test platform with a magnetic powder brake to load is presented based on the complete hardware design. Author has completed a variety of testing on this platform. The results showed that the new compound start control method based on the rotor pulse positioning and the back EMF zero crossing detection can ensure the normal start, acceleration and uniform running of the motor with load without the phenomenon of losing step and reversion, and external synchronization and synchronization switching in the process of motor to accelerate is smoothing.