IJRME – Volume 3 Issue 1 Paper 4


Author’s Name : Abhijeet Shirude | S. Y. Gajjal

Volume 03 Issue 01  Year 2016  ISSN No:  2349-3860  Page no: 15-19






During the assembly of machines the rotary shafts are aligned properly within the given specified tolerance limit. One of the major problem with rotating shaft is misalignment. Present technique available to find out the misalignment in rotating shaft is FFT (Fast Fourier Transform) analyzer. However an important deficiency of the FFT that it is not an effective tool to analyze non-stationary signals, so we lose the time information when a particular event took place. Then the Short-Time Fourier Transform is a modified version of the fourier transform invented to analyze the non-stationary signals. In STFT, the signal is divided into small enough segments, where these segments of the signal can be assumed to be stationary. The main drawback of STFT is that once a particular size time window is chosen, then the window remains same for all the frequencies. For vibration analysis of mechanical faults, presently the WT (Wavelet Transform) is developed as an alternative approach to the STFT to overcome the resolution problem. The DWT (Discrete Wavelet Transform) provides a time-frequency representation of signal. It allows the use of long time intervals where low-frequency information is desired and also takes shorter time intervals where high- frequency information is desired.


Misalignment in rotating shaft, FFT (Fast Fourier Transform), non-stationary signals, STFT (Short-Time Fourier Transform), WT (Wavelet Transform), DWT (Discrete Wavelet Transform), time-frequency representation


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