In other embodiments, the position sensor 38 includes one or more of the stator windings 28, allowing the radial position of the rotor 24 to be determined by measuring one or more electrical characteristics of the one or more of the stator windings 28. For example, the complex impedance of the stator windings 28 may change in response to the position of the rotor 24 relative to the stator pole 29 or poles that are associated with that stator winding 28. This sensing of the position of the rotor 24 may be accomplished using an optimal estimator such as a maximum likelihood estimator or an extended Kalman filter. Furthermore, where the rotor 24 is a solid or generally rigid structure, when a rotor-stator gap closes on one side of the rotor 24 the rotor-stator gap will open a corresponding amount on the other side of the rotor 24. A combination of measurements on opposite sides of the rotor 24 can be used to reduce noise in the position sensor 38 in either or both the independent sensor device and impedance methods of determining the radial position of the rotor 24.

In the block diagram of FIG. 2, the controller 32 is configured to perform a Rotor Adjustment Calculation using various sources of information to calculate both angle-based adjustments using the rotor angle 34 and non-angle-based adjustments that are independent of the rotor angle 34. The angle-based adjustments may be based solely on measured rotor displacements or have a feed-forward term that is a function of measured rotor speed or a previously identified stator magnetic field strength.