Abstract
The theory of cyclostationarity is widely used in condition monitoring of machines. It has been already discussed in many articles that the utilization of bi-frequency maps can be beneficial in case of local damage diagnostics. First of all, in this article the well-known spectral coherence method is recalled. Furthermore, a new bi-frequency map, namely coherent map, is proposed. It is based on coherent statistic. The performance of both approaches is compared in application to the real vibration data acquired on a gearbox operating in an underground mine. In order to simplify indication of the fault frequency, the enhancement of these maps is proposed on the basis of local maxima method extended to bi-frequency domain. Once the damage occurs, the local maxima should appear in the map due to cyclic amplitude modulation. We provide formulas for the range of local maxima along the cyclic frequency axis. The number of local maxima for a given cyclic frequency contains information about the modulation depth. We apply weights to local maxima and reflect them in the enhanced bi-frequency maps.
Published Version
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