Operational Modal Analysis of Journal Bearings Based on Stochastic Subspace Identification

Abstract

AbstractModal analysis of journal bearings is critical to their condition monitoring, dynamic analysis and damage detection by extracting the frequency, damping ratio and mode shape based on vibration response. Operational modal analysis (OMA) which just need the output-only response has been applied in civil engineering structures successfully. In this paper, the basic procedures of the popular operational modal analysis method, that data driven stochastic subspace identification (Data-SSI) and stabilization diagram is first introduced in details. Then, a five degree of freedom model is presented to verify the accuracy and robustness of the method in identifying frequency and damping ratio. And then, experiments under different operating conditions were conducted to acquire the vibration responses of journal bearings. The experimental modal analysis (EMA) method and Data-SSI were applied to identify free modal parameters and operational modal parameters separately. Finally, it is indicated that Data-SSI can identify modal parameters of journal bearings in operation effectively by comparing the modal parameters identified from Data-SSI with the peak values of spectrum.KeywordsOperational modal analysis (OMA)Journal bearingStochastic subspace identificationModal parameters