The Study Of Sensorless BLDC Motor Control System Based On DSP

This paper studied the sensorless control system of BLDCM using TMS320LF2407A DSP, discussed the current commutation and speed estimation technology of the BLDCM in detail, and designed the system hardware and software.In the paper, the development of BLDC motor in home and abroad is summarized firstly, various control methods of sensorless BLDCM are presented, and through comparing the advantages and disadvantages of these methods, this paper presents a novel detecting method of rotor position of BLDCM based on the third harmonic components of back emf.The method of indirect sensing the rotor position here is particularly applicable to trapezoidal back emf type of PM ac motors. For these types of motors, the open circuit stator phase voltages, also called back emf, have a trapezoidal shape that contains a fundamental and higher order frequency harmonics. In particular, the third harmonic component is extracted from the stators phase voltages while the fundamental and other polyphase components are eliminated via a simple summation of the three phase voltages. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any speed and load condition, and is practically free of noises introduced by the inverter switching, making it a very robust sensing method.Consequently, the third harmonic signal needs a phase shifter (FIPS), which can shift the zero-crossing point of the input signal with a specified amount of phase to command the inverter current switching. The detection performance of the proposed FIPS is independent of the frequency of the input signal and quite robust with respect to the measurement noise. It is shown that the proposed sensorless control scheme using the FIPS is more effective in the respects of noise-robustness and is more cost-effective than the previously known schemes.Finally, some experimental results are presented and some concluding remarks are given, which showed this method could achieve good performance for a wide speed range.