Sensorless adaptive control of permanent-magnet motors: Some asymptotic properties

Sensorless control of ac machines implies estimation rather than measurement of the rotor speed and/or position. While several publications on sensorless control of permanent-magnet synchronous motors have appeared, few so far consider estimation also of machine parameters (inductances and resistances). In this paper, it is shown that the information extractable from the fundamental frequency component of the stator currents is sufficient for estimation of speed, position, and the d direction inductance. The analysis shows that the asymptotic rotor position error at rotation can be substantially reduced through estimation of this inductance. At standstill, the initial rotor position is estimated. Convergence proofs are presented in both cases.