Wavelet analysis in a simple rotor's run-up process

A rotor run-up or run-down process can provide more useful information than normal conditions. A traditional difficulty associated with a rotor run-up or run-down analysis is the non-stationary nature of the vibration data. This paper compares Short-Time Fourier Transform (STFT) and the wavelets analysis in these non-stationary signal analyses. A Short-Time Wavelet Transform (STWT) is proposed to analyze these signals. Simulations and experiments in a simple rotor-bearing system show that both STFT and STWT can be used to analyze these non-stationary signals. The STWT can provide smoother and better results than STFT analysis in this case. From the amplitude-frequency curve obtained by STWT, the modal frequency and damping ratio are calculated. This paper also analyzes the characteristics of signals when the shaft touches a hoop in run-up process.