smoothen out noisy acceleration curve

Kimpan · Nov 26, 2009

I have a very noicy rotational acceleration curve from an impact to a dummy head. The impact has a duration of ~10ms and I wish to smooth it out without compromising the data. What type of filter is suitable for this?
I have been using a "sliding average" and butterworth filter but not sure which, if any, is good?
In the picture I have applied a sliding average that calculates the average of 20 points. The blue line has been filtered again with sliding average of 20 points.

GregLocock · Nov 26, 2009

Blue curve looks fine to me. We normally call it a moving average. The other obvious option is to fourier transform the entire signal, zero the high frequency ringing tone, and then IFT it back into the time domain.

However for crash data I think you'll find the regs specify what sort of filtering to use.

Cheers

Greg Locock

SIG

lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

sreid · Nov 30, 2009

The Savitzky-Golay smoothing filter is often considered the best.

http://www.mathworks.com/access/helpdesk/help/toolbox/signal/sgolay.html

GregLocock · Dec 1, 2009

" Although Savitzky-Golay filters are more effective at preserving the pertinent high frequency components of the signal, they are less successful than standard averaging FIR filters at rejecting noise when noise levels are particularly high."

Given that he has an S/N ratio of 0 dB I think I'd class that as high noise levels.

Cheers

Greg Locock

SIG

lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

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smoothen out noisy acceleration curve

Kimpan

Mechanical

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GregLocock

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sreid

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