Research And Implementation Of Sinusoidal-wave Control System For Brushless DC Motor

As a typical representative of mechatronical process, the brushless DC motor has received extensive attention due to its advantages, such as small size, light weight, high efficiency, low inertia and wide speed range. In addition, its corresponding mechanical characteristics is similar to the DC motor. Therefore, its traces can be found in the most areas which are from the aviation to exploration of the sea. The traditional 120 ° square-wave operation mode exists low defects, for example, torque ripple, large operating noise, energy efficiency and so on. Therefore, the research to find out an excellent strategy in the motor control system is more imperative.The sinusoidal waveform control system of brushless DC motor which was based on space vector pulse width modulation(SVPWM) has been studied. Firstly, the basic structure of the brushless DC motor was introduced. On this basis, the generating mechanism of rotating magnetic field and the motor operating principle were analyzed deeply. Considering of the air gap magnetic field distribution and the motor mathematical model in the three-phase coordinate system, the mathematical model of the motor in the d-q coordinate system was deduced, which demonstrated the feasibility of controlling brushless DC motor through decoupling.Next, sinusoidal pulse width modulation technique and space vector pulse width modulation technique were compared each other. The principle and algorithm of space vector pulse width modulation were discussed, which provided theoretical sources and design ideas to building the Simulation Module or writing software program. The sinusoidal waveform control system simulation mode based on operation mode was designed. The feasibility of controlling brushless DC motors by sinusoidal waveform was proved through the simulation waveforms.Again, a few key issues encountered in the process of designing the sinusoidal waveform control system, such as, the position and speed estimation, the start-up mode of motors, had been obtained comprehensive exposition. A PWM phase-shift technology had putted forward to solve the problem of current reconstruction easy to fail in low modulation areas.Finally, the experimental platform was designed. The hardware consisted of a master chip—STM32F030, power module, MOS driving module, current sampling module, overcurrent protection module, brake module. The software programs were written by assembly language, which were designed to finish the main structure of the program, the initialization procedure, trigonometric operation procedures, SVPWM operation program, phase current reconstruction program, PI adjustment program. Finally, hardware and software were debugged successfully. According to the recording and analysis of experimental data, the plan which was devised in this paper was feasible, practical and advanced.