Help Please : How to determine transfer function from two signals?

[comble]

Hello,

I am an intern in a research center and to do my experiment I need to use Labview. I have already managed to make VI for the signal generation and the aquisition data. But now I have to identify the transfer functin from the stimulus signal and the response signal. I would like to display the Bode diagramme and to identify thr transfer function itself.

It is quiet urgent I have to to this by the end f the week.

Sorry for my bad english...

Thank you for any help

Eva comble

[gwd]

Well there is Transfer Function.vi (haven't used it myself, but it sounds like what you are looking for).

You can find it by doing a search for "transfer" using the vi search function.

[comble]

Thank you for your response but this VI dont allow to identify the transfer function itself. What I would like to obtain is a numerical expression of the transfer function.

Thank you for any further help.

EVa comble

[gwd]

OK as I understand it now you are after an ANALYTIC equation for the transfer function.

This is "system identification" and to the best of my knowledge there is no vi that will do this. However there is a Labview toolbox (extra $$) that will do it (http://zone.ni.com/devzone/conceptd.nsf/webmain/3270D31FE08F91E18625703D0071553F).

If you are willing to accept a fairly simple model (say one pole or one zero) you might be able to take the array of numbers that come out of the transfer function vi and fit to a particular functional form using one of the Labview fitting vis.

[comble]

Thanks, I ´ve this Toolset and I am going to try.

Have a nice day!

Eva comble

[msa123]

hey i was looking into the forum to find if someone had problem like me

and found out that you were doing the same thing that i m trying to do

did u find out the way to find the transfer function of the system

i am having the same problem

as i have the data acquisition box

i give the input and get the response of the system but dont know how to find the transfer function

can you please help me with that

Thanks in advance

[msa123]

hey wanted to say i am the one who asked about the tranfer function few minutes ago

forgot to tell u my email id

 if you know the solution can you send me an email on msahuja@gmail.com

i shall be really thankful to you

Message Edited by msa123 on 09-25-2006 02:26 PM

[Nihil]

have any of you tried the "draw" box.

There's a box that writes the TF of the system. I don't rembember the example i saw it in, but look it up. it may help (if i understood correctly)

[Eli_S]

The questions in this thread are really regarding System Identification. The only way to do this is using the System Identification Toolkit. LabVIEW by itself cannot do this. Once the model (transfer function, state space, etc..) has been acquired through the use of this tool, more complex design and simulation processes can be done using the Control Design and Simulation Module