Sensorless position and speed estimation with improved integrator for PMLSM drive

This paper describes a sensorless position and speed detection algorithm designed for permanent magnet linear synchronous motor (PMLSM) drive. Measured line currents and terminal voltages are used to estimate the flux of the alpha-beta axis in stator frame, integrating the back electromotive force (EMF). Position and speed signals are derived from angle of the flux linkage and its change rate. A new improved integrator is presented and analyzed for compensate DC offsets and drift, which invariably exist in any practical implementation based on combination of low-pass filter, highpass filter and PI regulator. Experimental results are presented to show the realization of the objectives.