A novel method for BLDCM control based on phase back-EMF observation

Abstract

This paper proposes a new zero-crossing point detection method for BLDCM without using the position sensor. Regarding phase current and phase back-EMF as state variables, the observer model of the phase back-EMF could be obtained from derivation of the mathematical model of BLDCM. This observation model could observe the value of the phase back-EMF real-timely, and the zero-crossing point could be directedly detected through measuring the back- EMF at high speed. But the phase back-EMF is relatively smaller at low speed, and it is possible to cause unexpected commutation. A kind of zero-crossing point detection method is proposed based on this model for low-speed control. Combining the observation model and the zero-crossing point detection method, it could realize the zero-crossing point detection of the BLDC in full speed range. The simulation and experimental results show the feasibility of this method. © 2011 Springer-Verlag.