An amplitude modulation detector for fault diagnosis in rolling element bearings

As rolling element bearings begin to fail they induce characteristic fault frequencies in the vibration of an electric machine. These characteristic fault frequencies tend to modulate the electric machine's frequencies of natural mechanical resonance. Therefore, an amplitude modulation (AM) detector, similar to the bispectrum, is proposed. This new tool is especially designed to detect instances of AM when the measured magnitude of the characteristic fault frequency itself is not significant (e.g. incipient bearing faults). A normalized version of this detector is also presented to assist in the interpretation of results. Computer simulations as well as actual bearing vibration data are used to confirm the proficiency of this proposed AM detector in identifying bearing faults.