Damage Detection of a Rotating Cracked Shaft Using an Active Magnetic Bearing as a Force Actuator—Analysis and Experimental Verification

Detecting cracked rotors using auxiliary harmonic excitation

“…The peaks are located at the following excitation frequencies: 9, 18, 36, 45, 63, 72 Hz. All these frequencies fully satisfy condition (17) and apart from 36 Hz also condition (7). The highest peaks are near the excitation frequency of 36 Hz, i.e.…”

“…(7), or r = 2 and s= 1 in Eq. (17). The response only occurs at the rotor spin frequency (1X) and the AMB forcing frequency (18 Hz).…”

“…This means that q rs = 0 for 9s9Z2. The D rs +K 0 terms on the diagonal are generally far away from singularity, except for a lightly damped system when (rO+ sO 2 ) is close to a critical frequency of the system, that is o i ¼ rX þsX 2 , for some i, r and s (17) where o i is the ith critical frequency. Hence this condition must be satisfied to obtain a high steady-state response, and is the condition required to set the excitation frequency.…”

Comparison of Excitation Signals in Active Magnetic Bearing System Identification

“…Accurate models obtained by system identification are needed in order to design high-performance controllers (Noshadi et al, 2016), and they have an increasingly important role for diagnostic (Schuhmann et al, 2012) and monitoring purposes (Quinn et al, 2005), (Aenis et al, 2002), (Tiwiri and Chougale, 2014). A common choice for the excitation signal is a sine-wave-based spectrally rich signal, such as a multisine or swept sinusoid signal with a frequency content covering the desired frequency bands.…”

“…In addition, in (Garcia et al, 2016), PRBS is used for performance assessment of a bearingless motor to identify sensitivity functions. Moreover, in (Noshadi et al, 2016), (Inman et al, 2005), (Wroblewski et al, 2012), (Fang et al, 2013), (Tang et al, 2016), and (Lanzon and Tsiotras, 2005), chirp has been applied for the identification of rotor system dynamics. However, these studies do not provide any analysis of the obtained frequency responses as the main focus is on the identification for control, in other words, the models are evaluated to be representative in frequency regions that are relevant for control design purposes.…”