Position estimation in induction machines utilizing rotor bar slot harmonics and carrier-frequency signal injection

This paper presents a simple and robust way of utilizing harmonic saliencies created by rotor and stator slotting, present in some induction machine designs, for the estimation of rotor position. The injection of a carrier-signal voltage, in addition to the fundamental excitation, produces a carrier-signal current that contains the desired spatial information. A closed-loop tracking observer is then used to extract this spatial information for the estimation of the rotor position. Due to its reliance on a spatial saliency and carrier-frequency signal injection, the technique is very robust over a wide speed range, including low and zero speed.