Sensorless speed control of permanent-magnet motors with nonsinusoidal EMF waveform

A novel sensorless speed-control strategy for permanent-magnet AC motors (PMACMs) is presented. A nonlinear reduced-order observer and a high-gain observer are designed to estimate the induced EMF, without mechanical position or speed sensors. In contrast with previous proposals, the EMF estimation is performed without previous knowledge of its waveform. From the estimated EMF, the rotor speed and the position derivatives of flux are calculated and used for the implementation of a PMACM speed control without mechanical position sensor. The proposed strategy is not limited to PMACM with sinusoidal or trapezoidal EMF waveform. Moreover, it allows the PMACM ripple torque and copper losses to be minimised. The performance of the proposal is validated through simulation and experimental results.