Experimental Analysis of Frequency Response Function Estimation Methods for Active Magnetic Bearing Rotor System

System identification can be used in automated retuning of an active magnetic bearing (AMB) rotor system during commissioning. In the case of good signal-to-noise ratio (SNR), the identification measurements are more time effective using multisine excitation than stepped sine excitation. A multisine signal contains selected frequencies in the desired frequency range. Since in multisine excitation the signal distributes the power over F frequencies, the SNR of the measurement deteriorates. The SNR is improved by averaging the measured frequency response function (FRF) over several measurements. The purpose of this study is to investigate the suitability of different frequency response function estimators for an AMB rotor system identification. The results show that the most accurate estimator for this setup with non-synchronous measurements and the excitation used, is a joint-input-output estimator.