The CTIgram: A Novel Optimal Demodulation Band Selection Method and Its Applications in Condition Monitoring of Rotating Machinery

Theil index is an indicator proposed in the field of economics, developed from the concept of information entropy, used to measure the degree of difference in a system, and it can consider both overall and local differences. This article explores the application of the Theil index in bearing fault diagnosis and proposes the correlation Theil index (CTI). In order to use this indicator in bearing fault diagnosis, a tower-shaped distribution diagram called CTIgram is established. CTIgram adopts an adaptive multilevel spectrum segmentation method, which can well obtain the center frequency and bandwidth of the fault signal and adaptively divide the frequency band. The frequency band selected by CTI often contains more periodic pulse information. This method has great advantages in extracting fault information from signals with noise. The proposed method is shown to be effective by the simulation signal, and it was proved by the bearing outer and inner ring fault signals that this method can be applied to bearing fault diagnosis. The comparison experiments with fast Kurtogram (FK) and Gini index (GI) demonstrated the superiority of the method.