Research On Brushless DC Motors Control System

With the help of rapid development on power electronic technology and magnetic materials technology, brushless DC motor takes great advantages over traditional motor, such as brush DC motor, asynchronous motor and switch reluctance machine. This new kind of DC motor has been widely used as an important movement element in modern industrial field of automobile, aerospace and household appliances. The deep application requires a higher control degree on brushless DC motor. The further upgrade and an improvement on the machine itself and its control method is necessary. Therefore, it takes a great significance of the further research on brushless DC motor technology and its advanced control technology.The goal of this paper is to design a DSP-based controller and a brushless DC motor control system with the fuzzy control technique.First, the paper introduces the structure composition and working principle of DC motor,sets up two kinds of mathematical models: electric machine's differential equation and transfer function respectively, and makes analysis on motor's dynamic and static performances. An overall control system: current two-speed closed-up is proposed. According to the performance requirement of the system, the author selects TMS320F2812 DSP as control chip and confirms the implementation method on the control functionSecond, the control strategy of this system are studied in this paper. By using engineering design method, it confirms current and double closed loop controller's control strategy and control parameters respectively. For its fixed parameters characteristics,the disadvantage of traditional PI controller is its incompatibility between dynamic quality and stability precision. Hence, fuzzy control technology is introduced to improve the speed loop,and an adaptive fuzzy PI controller is designed to replace the traditional PI control mode. The automatically adjust execution of this kind of controller can be changed according to different control requirement. So the dynamic and steady performance during control process gains an effective improvement. In order to verify the effectiveness on control method and strategy, a brushless DC motor control system under MATLAB/Simulink environment is established in this paper. It simulates the experiments under two circumstances: traditional PI controller as speed loop and fuzzy self-adaptation PI controller as speed loop. Then the paper makes a contrast on rotating speed, torque and current curve of two experiments. The experiment results show that the control system of this paper has a higher control precision and a better robustness.Finally, the hardware and software of brushless DC motor's control system is being designed. The paper uses a block design by functional area as major design idea, then elaborates the designment on main circuits, such as DSP chip peripheral circuit, drive circuit,detection and protection circuit. The flow charts of main system module and interruption subroutine are given, then the ideas and application method on main system module are described, such as star subroutine, capture interruption subroutine and A/D interruption subroutine, etc.