An On-Line Torque & Flux Linkage Estimator for Permanent Magnet Motor Drives Based on the Instantaneous Voltage-Current Data

This paper describes the implementation and validation of an on-line torque and flux linkage estimator applied to a 3-phase permanent magnet AC machine. The estimator is based on the sampling of phase currents and the reconstruction of phase voltages from PWM duty cycles to determine the phase energy and the associated copper loss over a complete electrical cycle. From this and utilising the relationship between coenergy and torque with the psi-i locus, the resultant torque and instantaneous flux linkage can be estimated. The estimator is validated using a 3-phase interior permanent magnet AC machine operating with both sinusoidal and non-sinusoidal current waveforms. It is proposed that the resultant torque and flux linkage estimations can be integrated into an existing DSP motor controller to optimise steady-state performance and be used in on-line motor parameter monitoring and fault analysis/diagnostics