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From: FatScouser on 4 Jun 2010 08:30
>On Jun 4, 1:32=A0pm, "FatScouser" <john.hague(a)n_o_s_p_a_m.truebit.co.uk>
>wrote:
>
>> We have some truck suspension, ride-height, and other chassis data
(0-20
>> Hz) from which we need to extract frequency spectrum information.
That's
>> the problem.
>>
>> Rather than using FFT, which doesn't seem to handle the very few numbers
=
>of
>> wavelengths due to all the damping going on, I'm looking at the harminv
>> module developed by Prof. Steven G. Johnson (who posts on this forum).
Th=
>at
>> module assumes the signal is composed of a finite number of decaying
>> sinusoids - which sounds like it should fit our purposes, but am not
100%
>> sure, so any confidence from you experts would be great!!!
>
>Dear John,
>
>With all due respect, what you want frequency spectrum information
>*for*? Surely it is not of interest in itself.
>
>I do not know the harminv package, but if you are basically dealing
>with superimposed damped harmonic oscillators, then perhaps it is the
>thing. There must be many models of truck behaviour out there: why not
>start with one of those?
>
>illywhacker;
>

Thanks illywhacker (Illy?! Ilya?!)

We're analysing real data but are unsure of the source, so we can't build a
proper model unfortunately. There are only a few assumptions we can make
about the truck and its chassis. (Am I being vague again?)

John
From: Rafael Deliano on 4 Jun 2010 10:03
> We're analysing real data but are unsure of the source,
Coherence function might be usefull. Typical book is:
Bendat, Piersol "Engineering Applications of Correlation and Spectral
Analysis" Wiley 1993
http://www.amazon.com/Engineering-Applications-Correlation-Spectral-Analysis/dp/0471570559/ref=sr_1_fkmr0_1?ie=UTF8&qid=1275660095&sr=8-1-fkmr0

MfG JRD
From: illywhacker on 4 Jun 2010 11:33
On Jun 4, 2:30 pm, "FatScouser" <john.hague(a)n_o_s_p_a_m.truebit.co.uk>
wrote:
> >On Jun 4, 1:32=A0pm, "FatScouser" <john.hague(a)n_o_s_p_a_m.truebit.co.uk>
> >wrote:
>
> >> We have some truck suspension, ride-height, and other chassis data
> (0-20
> >> Hz) from which we need to extract frequency spectrum information.
> That's
> >> the problem.
>
> >> Rather than using FFT, which doesn't seem to handle the very few numbers
> =
> >of
> >> wavelengths due to all the damping going on, I'm looking at the harminv
> >> module developed by Prof. Steven G. Johnson (who posts on this forum).
> Th=
> >at
> >> module assumes the signal is composed of a finite number of decaying
> >> sinusoids - which sounds like it should fit our purposes, but am not
> 100%
> >> sure, so any confidence from you experts would be great!!!
>
> >Dear John,
>
> >With all due respect, what you want frequency spectrum information
> >*for*? Surely it is not of interest in itself.
>
> >I do not know the harminv package, but if you are basically dealing
> >with superimposed damped harmonic oscillators, then perhaps it is the
> >thing. There must be many models of truck behaviour out there: why not
> >start with one of those?
>
> >illywhacker;
>
> Thanks illywhacker (Illy?! Ilya?!)
>
> We're analysing real data but are unsure of the source, so we can't build a
> proper model unfortunately. There are only a few assumptions we can make
> about the truck and its chassis. (Am I being vague again?)

Yes - I am afraid you are. What do you hope to learn from the data
about the truck(s)?

illywhacker;
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