An analytical frequency-domain model of self-sensing magnetic bearing: modulation approach

This article introduces an analytical model of the self-sensing process in the self-sensing active magnetic bearings. In this model, the switching harmonics of the PWM amplifier and the demodulator’s output are expressed analytically in the frequency domain, thus the nonlinear self-sensing process can be regarded as a “virtual displacement sensor” with precise input-output relationships. Then, the sensitivity of the virtual displacement sensor is investigated, which indicates that the virtual sensor’s sensitivity not only has varying values with different system parameters but also deteriorates significantly in the high frequency region. Fortunately, an acceptable sensitivity of the virtual displacement sensor can still be maintained if the system is properly designed, which is also verified by experimental results on a four degree-of-freedom self-sensing radial AMBs rigid rotor platform.