Sensorless speed measurement of AC machines using analytic wavelet transform

A new method for the sensorless speed estimation of AC machines, using the analytic wavelet transform of the stator current signal, is proposed for a direct torque control drive. A comparison with results obtained using the short-time Fourier transform is included. The proposed method can be implemented in real time on a digital signal processor. The time-frequency resolution obtained and the computation time required by the proposed algorithm are improved in comparison to existing techniques, and the method can be applied over the entire speed range.