Re: System Identification -- An alternative to Transfer Function from Frequency Response Data

"anonymous" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I have some frequency response data (amplitude, phase and frequency)
> of a system that I collected using a frequency response analyzer and
> am trying to obtain its transfer function (poles and zeros).
>
> This general problem is addressed in
> http://www.mathworks.com/support/solutions/data/7423.shtml.  In short,
> I tried to use the invfreqs approach suggested in this link, but got
> horrible results.  The other suggestion mentioned is to use the
> 3rd-party Frequency Domain Toolbox ($950).  Other than buying a new
> toolbox, does anyone have any suggestions for obtaining the transfer
> function from frequency domain data?

I never tried using the frequency response.   I can't count on being able to
shake the system to the ground just to tune it.    I use least squares
system identification.  This requires that you know the number of poles and
zeros ahead of time or fit the data to many models and choose the best one.
You can do this with an Excel spread sheet, no fancy math package required
but it helps.

Peter Nachtwey