| This thesis firstly explains the composing structure and operating principles of brushless DC motor and then discusses the relevant control strategies of it. The brushless DC motor (BLDCM) is set as the control target. The design of hardware of control system is conducted on the basis of dsPIC30F2010 microprocessor. And a digital processing is realized by the combination of digital signal processing with relevant circuit. The hardware system contains dsPIC external circuit, position detection circuit, bridge power drive circuit, protective circuit, etc. Software system which is compiled by C programming language contains main routine, service subroutine and interrupt subroutine. The main routine is used for initialization of slug and the variable, while service subroutine is used for A/D transition, software phase conversion, PWM production, and so on. The interrupt subroutine is triggered by Hall position signal.Based on the analytical method of energy approach and Fourier expansion, the analysis of cogging torque of permanent magnet motor equipped with parallel-magnetized surfaced mounted magnets has been conducted. A further study on several kinds of weakening methods of cogging torque has been made, including cogging torque weakened by choosing proper pole arc coefficient, by asymmetric distribution of permanent magnet, by combination of different polar arc coefficients, or by changing the shape of permanent magnet. Meanwhile, determination methods of motor parameters in different ways of torque weakening are deducted. Finally, the results in different motor models are calculated and tested with finite element method, which proves the validity of the mentioned determination methods above.At last the 24V 500W BLDC prototype based on design intention is made. The prototype is then used for the experiment of control system designed in this thesis. It is proved by the experiment that the system is stable and efficient and the prototype runs well. |
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