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Due to the low operating efficiency and the complicated control of the traditional linear compressor, a resonant frequency tracking control method based on sliding-mode observer (SMO) is proposed in this paper. In order to obtain a better observation result of the piston stroke, a second order general integrator (SOGI) is used to filter the back electromotive force (EMF) signal obtained by sliding mode observer. According to the characteristic that the phase shift between the piston stroke and motor current is 90° when the linear oscillation motor (LOM) works at the resonance frequency, the average value of stroke-current product (ASCP) method is used to obtain the resonant frequency. The experimental result shows that the proposed SMO using SOGI filter can obtain a better steady-state accuracy compared with the traditional SMO using low pass filter and the resonant frequency can be well tracked by ASCP method.

resonant frequency， sliding-mode observer， second order general integrator， linear oscillation motor，