"Force" Window function

[logbook]

I have been asked to help code the "Force" window function in a C++ application. I did the original window functions rectangular, Hamming, Hann, flat-topped, and so forth, so I have the original papers by Harris, Nuttal etc, but I had never heard of the Force window until asked. I have googled it and found NI app notes (etc) which describe how good it is, but I can’t find which paper/book it is from or what the equation for the window is. Any clues?

 

[IRstuff]

huh... apparently, it's relatively well-known in certain circles:

http://www.dogpile.com/info.dogpl/s...-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/417/top/-/-/1

It's apparently a standard function in Labview and other frequency analysis equipment and software.


But a cursory scan found only this, so far:

A rectangular Window of adjustable Width used on the impact force signal in a Modal Analysis. Since the duration of the actual impact is usually very short relative to the overall digitised time sample, the frequency response function of the force signal can have a low signal to noise ratio. The force window does not alter the actual force pulse but minimizes the noise in the rest of the data block giving a much improved signal to noise ratio.

TTFN

 

[logbook]

Got it

The article on the Dogpile list titled "Modal Space" describes it. It's just a unity rectangular window around the region of interest and zero elsewhere.

Thanks IRstuff.

 

[IRstuff]

That's what they all seemed to say... But why the special name?

TTFN

 

[itsmoked]

As IRstuff's quote sez.. If this unity rectangular window is applied to "impact data" then some people will call it a "force" window.

You've heard of other things that are called by different names by different interest groups..

Example: Wiener Dog = Wire Haired Dachshund

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

- kcress@<solve this puzzle>

 

[logbook]

IRstuff. I read that quote you gave but failed to spot the relevant data. Perhaps it was just too simple. So I went off and hunted through the Dogpile list and found that Modal Space paper. Now re-reading your quote I see that the data was already there in plain sight and I just missed it. Scary!

 

[IRstuff]

Well, I would have done more looking also, since it sounded too simple to be correct ;-)

TTFN

 

[cincibcats]

Everyone is correct in that the "Force" window is basically a modified rectangular or uniform window around the impulse force signal for impact testing. However you might also want to add a cosine taper to the trailing edge of the window so that fewer high-frequency effects are added to the windowed signal.

 

[logbook]

Agreed, but when you are coding a standard window for application software your hands are tied with respect to the algorithm. The only possibility is to offer an "enhanced force" window function and explain what you have done in a manual.