| 英文摘要 | This paper proposes a cost-effective design of digital Brushless DC motor position servo system using the functions provided by TMS320F240 Digital Signal Processor(DSP). Firstly this paper introduces the task, content and significance of this project comprehensively. Combined with the development of the AC servo products in home and abroad, the paper describes the development trend of AC servo system in detail; Then this paper describes square wave and sine wave current drived permanent magnetic AC servo system comprehensively according to the theory of AC servo system, comparing merits and disadvantages of the two systems and describing the main parts of permanent magnetic synchronization servo system. Then this paper analyzes the whole system from the point of view of whole design: Combined with mathematical model of brushless DC motor, this paper describes voltage equation, torque equation, state equation and equivalent circuit according to the structure and theory of brushless motor, analyzing the ripple torque of motor and proposing two methods of restraining ripple torque, i.e. overlap and PWM methods. Based on the analysis of the above, it proposes the whole scheme of AC servo system, disparting as main circuit, position detection, rotor position detection, velocity detection, current detection, velocity modulation and current modulation parts. The paper then discusses the realization of the control system in detail. Firstly it describes the TMS320F240DSP and regulation of orientation logic comprehensively. The order of power supply of three-phase winding rests with three pulse signals produced by rotor position detector, which is the theory of changing orientation electrically, substituting for changing orientation mechanically; Then the paper describes PWM circuit, the production of PWM wave, velocity and position detection circuit, theory and realization of A/D circuit, protection circuit---watchdog and real-time interrupt module, above which it expatiates on the design idea of this three closed loops system (position, velocity and current loops), and it also describes the interrupt structure of DSP and algorithm of software in detail. The paper shows the frame chart of each loop of control system, analyzing from current loop to velocity, position loop; it also figures out dynamic response and important parameters of each loop according to control theory. The paper lists the outcome of experiment on this system and compares the outcome of experiment and theoretical calculation, proposing ideas of improving on this system. The drive system we made runs steadily in low speed, timing range 1:5000, position precision one pulse. From the above, we can see that the digital AC servo system we made fully meets the proposed requirements. |
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