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From: "Yuji Zhang" <yuji.zhang@tufts.edu>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Integration with experimental data
Date: Mon, 17 Jun 2013 19:10:13 +0000 (UTC)
Organization: Tufts University
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Nice explaination! Thanks tideman!

Is there a book or something where I can read about details of this issue - like quantitative implementation? Any recommendation is appreciated. Thanks everyone~ 


TideMan <mulgor@gmail.com> wrote in message <3bbe487c-22a8-4e9a-9c65-94200a9aadc1@18g2000prd.googlegroups.com>...

> You've got it arse about face.
> For integration, you need to high-pass filter.
> Consider y=cos(wt)
> it integrates to 1/w sin(wt)
> and integrates again to -1/w^2 cos(wt)
> which is -y/w^2
> So, if w is small, the acceleration gets scaled up by much more than
> if w is large.
> Therefore, any low frequency noise in the signal gets amplified.
> This results in the displacement derived from double integration of
> the acceleration wandering all over the place and perhaps heading off
> to + or - infinity.
> Perhaps this is why "the output isn't what we expected".
> IMHO it has nothing to do with cumtrapz, which works fine, just as
> cumsum would.
>