Extraction of periodic modulation of rotational speed from roller bearing vibration signals using a modulation template matching algorithm

The periodic modulation of the rotational speed of a machine element such as a bearing element is recognized as a valuable feature in characterizing the physical condition of the machine component. A time domain template matching algorithm is introduced as a non-linear frequency modulation estimation technique for extracting this feature out of a vibration signal from a damaged machine component. The technique is applied to data taken from a damaged railroad car roller bearing. The results are compared with those obtained using a more standard baseband phase demodulation technique. Although the template matching algorithm is computationally expensive, it can be applied to a limited duration raw input signal, resulting in a set of well defined parameters, unlike the baseband demodulation technique which relies on filtering and synchronous averaging over a lengthy time duration.