Researeh On Digital Speed Control System Of Brushless DC Motor

Permanent Magnet Brushless DC motor replaces the mechanical brush in a DC motorusing electronic commutation. It has DC motor’s good speed performance, and also has theAC motor’s characteristics of simple structure, so that it is reflects a number of advantagesin the application.Stable and reliable brushless DC motor operation is based on accurate rotor positiondetection. There are two ways of position detection, and they are position sensor positiondetection and sensorless position detection. However, the DC motor position sensorincreases the motor size, costs and reducing the stability of its operation, limiting theapplications. The requirements of the stability of the motor control system and the furtherexpanding of the brushless DC motor applications in the modern.Industrial applications have been improved, and this made the studying of the positionsensorless motor control system has further more theoretical worth and practical value.This paper studied a sensorless brushless DC motor digital speed control system using TI’sTMS320F2812MCU as the main control chip.Firstly, this thesis introduced the compositions, basic working principle, speed controlmethods and mathematical model of brushless DC motor in details, and introduced theposition detection methods using a position sensorless on the stage and the starting ways ofmotor with emphasis.Secondly, this paper studied the conventional method of Back-EMF position detection,and gave a new brushless DC motor rotor position detection method base on theH_pwm-L_pwm modulation technology. The experiment results validated this methodhaving a good performance on the rotor position detection. In order to deal with the startingproblem of position sensorless motor, this paper proposed a starting method using apredetermined position with a combination of step-up-start method, and the results verifiedthe feasibility of this method.Thirdly, this paper established the whole control system simulation model based on thebrushless DC motor mathematical model using the strong simulation function of matlab.Further more, this paper simulated the conventional PI control algorithm and fuzzyself-adaptive PI control algorithm, and the simulation results showed that the performanceof the system using fuzzy self-adaptive PI control algorithm has been improved significantly.Finally, this paper designed the hardware circuit and software codes of the brushlessDC motor control system, and debugged the whole system. The experiment results verifiedthat the speed regulation system has the same performance as the expected.