IDENTIFICATION AND COMPENSATION OF COGGING AND FRICTION FORCES IN TUBULAR PERMANENT MAGNET LINEAR MOTORS

This paper presents the modeling, identification, and compensation of cogging and resistive forces in tubular permanent magnet linear motors (PMLMs). An observer-based model that includes the effects of cogging, backlash, inertia, Coulomb, and viscous frictions, as well as back electromotive force is presented. Least square optimization is carried out to identify the model, and the weakness of fast Fourier transform (FFT) in PMLMs with short translators for precise wavelength determination is discussed. The identified model is used as a directional estimator in a closed-loop controller to compensate the disturbance forces induced by the PMLM to a secondary mechanism. Experimental results show a reduction of the disturbance force energy up to 31.96 dB.