I am working on bearing faults detection. I am doing the following steps:
signal->mean zero->high pass->hilbert->y->fft->cepstrum of y. this is my spectrum after hilbert and fft

this is the cepstrum

my code is:

    analy = hilbert(Signal);
    y = abs(analy);
    N = 2*2048;T=N/Fs;
    sig_f = abs(fft(y(1:N)',N));
    sig_n = sig_f/(norm(sig_f));
    Signal_fft_hilbert = sig_n;
    freq_s = (0:N-1)/T;    

      title ('Average FFT after Hilbert enveloping');
     xlabel('Frequency in Hz')


The problem is I am not able to extract the fundamental frequency out of the spectrum or cepstrum. my bearing frequency is 42 Hz.I am not getting prominent peaks in this region. Please suggest something.

  • $\begingroup$ The spectrum appears to have a fundamental frequency and third and fifth harmonics -- all of which are below 200Hz. Are you sure the bearing frequency is 42Hz? There are other frequencies related to it (electromotores.com/PDF/InfoT%C3%A9cnica/EASA/…: FTF, BSF, BPFO, BPFI that may be relevant). $\endgroup$ – Peter K. Mar 3 '14 at 12:56
  • $\begingroup$ well yes the bearing frequency is 42 Hz.and I am taking the cepstrum after fft. Is that correct? Or i need to take it after hilbert transform? $\endgroup$ – user3217416 Mar 4 '14 at 1:32
  • $\begingroup$ Oh I get your doubt. It is the fundamental ball frequency. $\endgroup$ – user3217416 Mar 4 '14 at 7:31

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