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.

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to improve the efficiency and/or expand the operational range of a conventional generator, with particular applications to wind turbines, hybrid vehicles, and so on. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with the active control system, which adjusts the overlap ratio based on the desired output power at different input speeds, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator at low speeds results in a reduced torque loss of the generator and an increased rotational speed of the generator rotor.