Development Of Permanent Magnet Brushless DC Motor Speed Control System With High Accuracy

The research background of this paper was the development of a certain type of control moment gyro (CMG) high speed rotor life test system. A certain type of brushless direct current motor was selected as the research object. A high precision speed control system of the brushless direct current motor was developed as the test system supporting device.According to the development task, overall scheme design and system was selected and determined. The C8051F120 single chip and MC33035 motor special-purpose chip was used in the system and the motor closed-loop speed control was fulfilled. The accuracy control of the motor speed was reached by the speed PI regulation and precision numerical control voltage source.After that, the hardware and software design of the speed control system was analyzed in detail on the basis of the design scheme. The hardware circuit was introduced in the hardware part. The designs of the motor driving module, the closed-loop speed control circuit, the motor running monitoring module, temperature measuring circuit, the protective circuit, the keyboard and display circuit and hardware reliability were achieved. A variety of precision components was used and the motor monitoring circuit was reasonably designed to make sure the accuracy requirement of phase current, motor voltage and axle temperature resistance signal. The high speed optical coupling isolation device and reasonable grounding measures were used to guarantee the reliability of the system.The modular design method was used in the software part to drawn the flow diagrams of every modular. The equal precision measuring frequency method was used to reach the precision measurement of rotating speed. System initialization programming was finished and the rotating speed PI control, the AD conversion of the monitor signal and the main modules such as the keyboard and display were programmed.At last, the debugging process of the key parts of the circuit and the program was presented, as well as the performance test of the whole machine. It is found that the speed control system can realize the high precision control of the motor. And the requirements of performance and indicators of the system development can be fulfilled.The development of the design process was summarized and the trend of improvement was presented in the further work.