Research On Control Strategies Of Brushless DC Motor

Brushless DC motor(BLDCM) is a typical mechatronic product. It uses electronic commutation to replace mechanical brush and mechanical commutator, and so it technically superiors to brush motor. As the BLDCM does not have brush and mechanical commutator, it reduces unreliability and mechanical noise. Adopting microprocessor control technology, it is more efficient than that of brush motor, increased by 15% to 20%, and it prolongs life expectancy about 6 times. With the rapid development of the power electronics technology, modern control theory and new magnetic materials, and the quicker switching frequency of power components, BLDCM and control technology has a breakthrough. This motor has an excellent linearity mechanical characteristic and control characteristic, and has a lot of advantages, such as reliable performance, low failure rate, small no-load current, wide speed range, small volume, easy maintenance, small noise, etc. It does not exist a series of problems about the brush, so that this kind of motor control system has great application potential.Firstly, this paper introduces the characteristics, development and research significance of BLDCM, the research current situation and the analysis at home and abroad, the main research contents and research targets, etc. Secondly, the basic structure and working principle, mathematical model and operating characteristics of the BLDCM are described in detail, and its operating characteristics include starting characteristic, working characteristic, speed characteristic and mechanical characteristic. Thirdly, this paper discusses several control strategies of BLDCM, introduces their controller design, analyses and compares advantages and disadvantages of these control methods. Finally, with the analysis of square-wave current and sine-wave current drive methods about the non-ideal back emf for BLDCM, torque ripple is researched in the process. And the results show sine-wave current drive is more effective to suppress torque ripple.To prove the rationality of theoretical analysis, this paper uses MATLAB/Simulink software to simulate it, and builds experimental platform to verify it. Three control strategies that include PID control, sliding mode variable structure control(SMVSC) and active disturbance rejection control(ADRC) are analyzed by Simulink software simulation. Torque ripple is researched on square-wave current drive and sine-wave current drive. In addition, this paper sets up test systems, including hardware design, software design and anti-jamming design of hardware and software, to study the BLDCM control system. In the implementation of hardware circuit, this paper designs the power circuit, clock circuit, reset circuit, control circuit, drive circuit and protection circuit, etc. Software program mainly designs in the integrated development environment (CCS), which includes main program designe, interrupt subroutines designe and anti-jamming designe of software, etc.Through the software simulation and experimental systems, it can come to a conclusion. The results show that these methods in this paper are correct and effective.