  Sensorless control of Permanent-Magnet Synchronous Motors (PMSM) at low
velocity remains a challenging task. A now well-established method consists in
injecting a high-frequency signal and use the rotor saliency, both geometric
and magnetic-saturation induced. This paper proposes a clear and original
analysis based on second-order averaging of how to recover the position
information from signal injection; this analysis blends well with a general
model of magnetic saturation. It also proposes a simple parametric model of the
saturated PMSM, based on an energy function which simply encompasses saturation
and cross-saturation effects. Experimental results on a surface-mounted PMSM
and an interior magnet PMSM illustrate the relevance of the approach.
