A New Approach to Extract Modal Parameters form Non-stationary Vibration Signals

A traditional difficulty associated with rotor run-up or run-down analysis is the non-stationary nature of vibration data. This paper compares Short-lime Fourier Transform (STFT) and the wavelets analysis in these non-stationary signal analyses. An Adaptive Wavelet Analysis (AWT) is proposed to analyze these signals. Simulations and experiments in a simple rotor-bearing system show that both STFT and AWT can be used to analyze these non-stationary signals. The AWT can provide smoother and better results than STFT analysis in this case. From the amplitude-frequency curve obtained by AWT, the modal frequency and damping ratio are calculated, This paper also analyzes the characteristics of signals when the shaft touches the outer hoop in a run-up process. In the touching process, the response signal is complex. The AWT can give a good result in this complex dynamic analysis.