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Topic: numerical integration
Replies: 5   Last Post: Mar 20, 2013 2:43 PM

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Loren Shure

Posts: 991
Registered: 12/7/04
Re: numerical integration
Posted: Mar 20, 2013 8:54 AM
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"Nasser M. Abbasi" <nma@12000.org> wrote in message
news:ki743g$6cg$1@speranza.aioe.org...
> On 3/18/2013 5:10 AM, JankoZ wrote:
>> Hi I need your help!
>>
>> I have measurement of acceleration in axis X,Y,Z (cca 6000 measurement
>> with spet 0.02sec).
>>I want to get final position with using Numerical Integration in Matlab.
>>Can anybody help me?

>
> Numerical integration can be hard to get right for this.
>
> Better to do this in frequency domain using FFT.
>
> Take the FFT of acceleration data. Since displacement is integration
> 2 times in time domain, then in frequency domain it becomes division
> by -(n*w1)^2 where w1 is the fundamental frequency of the acceleration
> signal (i.e. 2*pi/T) and n is the coefficient (i.e. bin) number.
> i.e. n=0..N-1
>
> Then you do ifft on the result.
>
> If you want just velocity, then divide by (I*n*w1) instead and
> do the same.
>
> This is what I do. It works well. But if you really want to
> do numerical integration, then get the AbraVibe matlab toolbox by
> Anders Brandt, it has a well written timeint() function. Apply
> it 2 times on your data. (for each x,y,z)
>
> --Nasser
>



I believe the original data were not evenly sampled, making an FFT (or
filter) solution problematic. Was that just a typo in the data?

--
--Loren

http://blogs.mathworks.com/loren




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