system identification toolbox

I need to find transfer function equation by using MATLAB System Identification Toolbox. But in this GUI, I only get polynomial equation.

My question is, how to convert this polynomial equation to transfer function equation?

hope you can help me.. Thanks...

Answer 1

[Rajiv Singh]

• If you use Output-Error (OE) model structure, then the ratio of the polynomials B and F is your transfer function: TF := B(q)/F(q)
• You can export any identified model into MATLAB workspace and run TFDATA command on it to fetch numerator (Num) and denominator (Den) polynomials. Then the transfer function is Num/Den.
• In release R2012a, you can identify a transfer function model directly in the GUI. Use Estimate popup menu option "Transfer Function Models".
• You can convert an identified linear model into TF model of Control System Toolbox by using "TF" command, as in: sys = tf(sys, 'measured').

[tiara]

Thanks for your respond...

I already use ARX model and not used Output-Error (OE) for this system identification toolbox.

How can I export identified model into MATLAB workspace?

Can you explain the step to export identified model into MATLAB workspace?

How to run TFDATA command on it to fetch numerator (Num) and denominator (Den) polynomials?

Thanks a lot...

[Rajiv Singh]

From the GUI, you can drag the identified model and drop it on to the "To Workspace" icon. This drag-and-drop action will export the mode to workspace. Then you can run TFDATA command on it; the documentation explain the TFDATA command:

http://www.mathworks.com/help/toolbox/ident/ref/tfdata.html

Answer 2

[tiara]

Thanks for your respond...

I already use ARX model and not used Output-Error (OE) for this system identification toolbox.

How can I export identified model into MATLAB workspace?

Can you explain the step to export identified model into MATLAB workspace?

How to run TFDATA command on it to fetch numerator (Num) and denominator (Den) polynomials?

Thanks a lot...