Observer-based sensorless control of a five-phase brushless DC motor

This paper presents a rotor position estimation technique for a five-phase permanent magnet synchronous motor with independent phases, based on a back-EMF observer. The method involves the use of a proper linear transformation which allows representing the five-phase motor by an equivalent two-phase model. Due to its characteristics, the sensorless strategy can be used in multi-phase motors having non-sinusoidal back-EMF shape, such is the case of brushless DC motors used in fault-tolerant applications. After an overview of the back-EMF model for the five-phase motor, the linear transformation and the observer-based estimation technique are presented. Experimental results show the overall performance during transient and steady-state operation.