Separating Harmonic Spectra
in [DSP]
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From: Greg Berchin on 30 Nov 2007 11:50 I'm dealing with a signal generated by a rotating machine. I am trying to separate components generated by an anomaly that occurs exactly once per revolution from those generated by an anomaly the occurs exactly twice per revolution. Of course, harmonics of the twice-per-revolution anomaly overlay harmonics of the once-per- revolution anomaly. Seeking suggestions on what analyses to perform to separate the two. My initial guess is that phase will somehow be the discriminating factor. Thanks, Greg
From: John E. Hadstate on 30 Nov 2007 17:01 "Greg Berchin" <gberchin(a)sentientscience.com> wrote in message news:db44a883-dd60-426b-8719-5bb98a602249(a)s12g2000prg.googlegroups.com... > I'm dealing with a signal generated by a rotating machine. > I am > trying to separate components generated by an anomaly that > occurs > exactly once per revolution from those generated by an > anomaly the > occurs exactly twice per revolution. Of course, harmonics > of the > twice-per-revolution anomaly overlay harmonics of the > once-per- > revolution anomaly. Seeking suggestions on what analyses > to perform > to separate the two. My initial guess is that phase will > somehow be > the discriminating factor. > > Thanks, > Greg The event that happens twice per revolution shows up once by itself and once combined with the event that happens once per revolution. Any chance of phase-locking to the "by itself" event, subtracting it out of the "once-per-revolution event" and then processing the events as separate streams?
From: Ron N. on 30 Nov 2007 18:02 On Nov 30, 8:50 am, Greg Berchin <gberc...(a)sentientscience.com> wrote: > I'm dealing with a signal generated by a rotating machine. I am > trying to separate components generated by an anomaly that occurs > exactly once per revolution from those generated by an anomaly the > occurs exactly twice per revolution. Of course, harmonics of the > twice-per-revolution anomaly overlay harmonics of the once-per- > revolution anomaly. Seeking suggestions on what analyses to perform > to separate the two. My initial guess is that phase will somehow be > the discriminating factor. If the impulse response of the once per cycle event spans less than an entire revolution, then you could periodically window outside that span in the time/angular domain and see what spectra is left from the other half of the revolution. To find each event, you could try a pair of angular windows 180 degrees apart, and rotate them together until until you find some sort of maxima in the difference between the two spectra. IMHO. YMMV. -- rhn A.T nicholson d.0.t C-o-M
From: John O'Flaherty on 1 Dec 2007 18:00 On Fri, 30 Nov 2007 08:50:15 -0800 (PST), Greg Berchin <gberchin(a)sentientscience.com> wrote: >I'm dealing with a signal generated by a rotating machine. I am >trying to separate components generated by an anomaly that occurs >exactly once per revolution from those generated by an anomaly the >occurs exactly twice per revolution. Of course, harmonics of the >twice-per-revolution anomaly overlay harmonics of the once-per- >revolution anomaly. Seeking suggestions on what analyses to perform >to separate the two. My initial guess is that phase will somehow be >the discriminating factor. Odd harmonics of the 1/per won't be duplicated in the 2/per. -- John
From: John O'Flaherty on 1 Dec 2007 18:01
On Sat, 01 Dec 2007 17:00:38 -0600, John O'Flaherty <quiasmox(a)yeeha.com> wrote: >On Fri, 30 Nov 2007 08:50:15 -0800 (PST), Greg Berchin ><gberchin(a)sentientscience.com> wrote: > >>I'm dealing with a signal generated by a rotating machine. I am >>trying to separate components generated by an anomaly that occurs >>exactly once per revolution from those generated by an anomaly the >>occurs exactly twice per revolution. Of course, harmonics of the >>twice-per-revolution anomaly overlay harmonics of the once-per- >>revolution anomaly. Seeking suggestions on what analyses to perform >>to separate the two. My initial guess is that phase will somehow be >>the discriminating factor. > >Odd harmonics of the 1/per won't be duplicated in the 2/per. Whoops, said it backwards. -- John |