Research On The Control Of Sensorless Brushless DC Motors

With the development of power electronics technology, microelectronic technology and the new permanent magnet materials, the technology of BLDC is changing. BLDC use electronic commutation instead of traditional mechanical commutation. BLDC not only inherits the advantages of the traditional DC motor, it has the advantages of high effic iency, no spark, more small and so on. BLDC has been applied in many fields,but BLDC use position sensor to detect its position. Those sensors can't work in some conditions. At Present, sensorless control has become a development trend of control technique for brushless DC motors.We mainly study the control system of sensor less Brushless DC motor. In chapter two, the structure, the working mechanism of brushless DC motor, mathematical mode and get back-EMF are introduced and analyzed in detail. The controller does not get the position of the rotor at the beginning of start as we study sensor less Brushless DC motor. In chapter three, we make study on the starting and a novel start-up method is proposed which called compound starting. It consist three steps: initial rotor Position, Position closed-loop starting, turning to back-EMF driving. The simulation and experimental results have demonstrated its well starting performance. In chapter four, we get the torque ripple of the BLDC is mainly due to the no ideal back-EMF and commutation. We designed about the BLDC-DTC for no ideal back-EMF and commutation current control for commutation. The torque ripple is effectively suppressed with this method.Based on Matlab and STM32F103 processor, this paper developed simulation system and hardware system. Control system can greatly meet the required Performance and the experimental results have shown the accuracy, rapid response and high reliability of the proposed method.