Acceleration to Position - PSD? Energy Spectrum?

[signal1]

How is position and velocity calculated from acceleration in the frequency domain?  

That is, acquire acceleration data, convert it via fft into frequency, filter to different response ranges and single or double integrate to velocity or position.  This gives a waveform. 

So is position and/or velocity the power spectral density of the resultant waveform?  Or is it the energy spectrum?  Perhaps it’s the peak to peak?  Any of the above? 

How do the minimum, maximum and average position/ velocity values get calculated from acceleration frequency data? 

Thanks,

Bob

[Andy F.]

Bob,

Are you actually trying to implement these concepts in DASYLab or LabVIEW?  Or do you have more theoretical questions about what information you can get out of FFTs of acceleration data, PSDs, etc.?  If its the latter then you will probably get a better response in a math-based forum.  Is there a particular application for this type of application?  Why couldn't you just integrate your acceleration data to get velocity and then again to get position? 

Please let me know.  Thanks!
Andy F.

[signal1]

Hi, Andy and thanks for your reply. 

In answer to your questions, DASYlab, deeper theory would be nice but I'd prefer more basic information first, application is acceleration response/conversion to frequency domain/integration is needed.  

But even the integration isn't as straightforward as it might seem.  For example, if a running integration is used you get a cumulative integration.  If you use block integration, it depends on how many blocks you integrate for and if you use any weighting per block or number of blocks.  And when so many of the same quesions apply for the FFT side it gets extremely variable. 

As for outputs, it would be useful to know if there is a physical description of any of these results.  For example, does the PSD in velocity mean average surface velocity or maximum or something else entirely?   What does the energy spectrum translate into - say for position?  Does a peak to peak measure (which may be very narrow in frequency or power) actually translate into maximum peak to peak for the surface?   I'm hoping someone can say what results the actual physical measurements translate to. 

Thank you,

Bob

[Angela M]

Hello Bob,

It does sound like you are asking about the theory, which I agree with Andy may be better answered by a math forum.  I'm afraid in the physical sense your question is not quite clear.  Are you trying to get from say a PSD in Velocity to Position in some way?  If you are asking for specifics on how a DASYLab function works behind the scenes, that I cannot say.

I am sorry for the confusion, can you rephrase your question?

Regards,

Angela

Applications Engineer