ON THE INVESTIGATION OF VIBRATION SIGNALS USING JOINT TIME FREQUENCY ANALYSIS

Abstract

This paper addresses the problem of coupled blade bending and shaft torsional vibration signals using the Joint Time Frequency Analysis (JTFA). Simulation results for the blade bending and shaft torsional vibration are studied using the Fast Fourier Transform (FFT) and the JTFA. The FFT spectra showed little information on the nonlinear dynamic interaction between the blade bending and the shaft torsional vibration; and thus cannot be used as a tool for monitoring the blade vibration by looking into the shaft torsional vibration signal. In contrast, the JTFA in the form of Wigner Ville Distribution (WVD) has given more useful information and reflected the dynamic interaction between different vibration modes on one side and between the blade vibration and the shaft torsional vibration on the other side. The obtained WVD representations of the shaft torsional vibration showed frequency layers that represent blade vibration activity.