Research Of Rotor Position Detection Method For PWM-ON-PWM Modulation Of BLDCM

PWM_ON_PWM modulation is the best way of PWM modulation for brushless DC motor proposed in recent years.Because Waveform of the terminal voltage conctoled by PWM_ON_PWM modulation is different from ones conctoled by other two PWM modulation.At present, the sensorless method to detect the rotor position,suited to half-bridge and full bridge modulation, isn't applicable. Therefore, the paper proposes a new approach to get the rotor position signals by detecting the line voltage difference zero-crossing, and based on this approach, DSP control system for brushless DC motor without sensor is designed successfully.Firstly, The paper simply introduces the background and investigative Status of the Field, lists the research content of the subject. It analyzes principle and mathematical model of BLDCM, on the basis, line voltage difference rotor position detection method is deduced.Secondly, on the basis of electric elementary diagram of BLDCM, By using the SIMULINK library module, Converter,Motor,Detector,Decoder and Generator are set up, which constitutes BLDCM's overall simulation model. And line voltage difference detection module is also established to observe the line voltage difference waveform to verify the theoretical resultsThirdly, this article has highlighted the design methods of hardware circuit consisted of power driver circuit, DSP smallest systems, line voltage difference detection circuit, isolate the circuit, power supply circuit and speed control circuit. as well as the design ideas and methods of system software consisted of the initialization subroutine,starting subroutine,updating comparison value or commutation subroutine, AD interrupt service routine, and speed control programFinally, experimental results are given and analyzed in detail. The results show that the proposed method can accurately detect back EMF zero-crossing point of BLDCM'winding controled by the PWM_ON_PWM modulation.