Higher Order Spectral Analysis: a Tool for Fault Monitoring and Diagnostics

This paper concerns the application of signal processing techniques based on the Higher Order Spectra (HOS) to the condition monitoring of mechanical systems. These techniques give more information than the linear spectral analysis and are particularly useful in situations where only a single measurement sensor is available. A simple model is presented and analysed with the aim of showing the effectiveness of the so called “polyspectra” in detecting different kinds of system non-linearities. The HOS analysis is used to interpret the signal structure and the system’s physical characteristics. Particular effort is made in order to give an interpretation of the structure of the HOS estimators. The results show that both the third and the fourth order spectra seem to provide a possibility of using HOS analysis as a tool for the condition monitoring and diagnostics of mechanical systems.