Improved state observers for sensorless single phase BLDC-PM motor drives

Two methods of extracting the rotor position and speed for a sensorless single phase BLDC-PM motor drive by measuring only the phase current are presented here. Both methods are based on a generated orthogonal flux system. The first method extracts the position information by using the tan^-1 function and then an improved observer is created by adding a 4^th order harmonic term in the estimated position, while the second method uses a phase locked loop structure. The proposed state observers are detailed using simulation results and then validated by experimental results.