A New On-Line Torque Estimator for Brushless Permanent Magnet Motor Drives: Validation through the i-/spl psi/ Diagram

This paper describes the use of the current-flux-linkage (i-Psi) diagram to validate the performance of an on-line torque estimator. An early step in the torque estimation is the use of controller duty cycles to reconstruct the average phase voltage waveform during each PWM switching period. Experimental validation of this reconstructed waveform with the actual PWM phase voltage waveform is impossible due to the fact that one is PWM in nature and the other is the average value during the PWM period. A solution to this is to determine the phase flux-linkage using each waveform and then plot the resultant i-Psi loops. The torque estimation is based on instantaneous measurements and can therefore be applied to any electrical machine. The paper includes test results for a 3-phase interior permanent magnet brushless AC motor operating with both sinusoidal and non-sinusoidal current waveforms