Analysis of Blade Tip Timing Data From Nonuniformly Spaced Sensors by Discrete Wavelet Transform

Abstract A major drawback of the blade tip timing (BTT) method is its inherent undersampling of the vibration data. The consequence of this characteristic is that the spectrograms computed using these data are very difficult to read as the spectral traces produced by the signal components are replicated multiple times due to aliasing. This paper describes a technique that exploits the nonuniformity of the sensor spacing to suppress aliasing. The analysis starts with the time–frequency representation of the signal obtained through a discrete wavelet transform (DWT). Then, the dominant response component is identified by searching from the highest ridge of the spectrogram. Finally, the corresponding signal component is removed from the spectrogram together with their replicas. The procedure is repeated iteratively until all the relevant signal components are isolated and identified.