User`s guide

3 Linear Model Identification
11 (Prediction-error method only) To stop the search and save the results
after the current iteration has been completed, click Stop Iterations.To
continue iterations from the current model, click the Continue iter button
to assign current parameter values as initial guesses for the n ext search.
12 To plot the model, select the appropriate check box i n the Model Views
area of the System Identification Tool G U I. For m ore information about
validating models, see “Overview o f Model Validation and P lots” on page
8-2.
If you g et an inaccurate fit, try estimating a new model with different o rders
or structure. You can export the model to the M A TLAB workspace for further
analysis by dragging it to the To Workspace rectangle in the System
Identification Tool GUI.
How to Estimate Polynomial Models at the Command
Line
• “Usingarxandiv4toEstimateARXModels”onpage3-60
• “Using pem to Estim ate Po lyn omial M odels” on page 3-61
Using arx and iv4 to Estimate ARX Models
You can estimate single-output and multiple-ou tp ut ARX models usi ng
the
arx and iv4 commands. For information about the algorithms, see
“Algorithm s for Estima ting Polyno mial Models” on page 3-6 6.
If you are estimating a multiple-output ARX model, you must specify order
matrices in the MATL AB workspace before estimation, as described in
“Options for Multip le -In put and Mu ltiple-Outpu t ARX Orde rs” on page 3-64.
For single-output data, the
arx and iv4 commands produce an idpoly model
object, and for multiple-output data these commands produce an
idarx model
object.
You can use the following general syntax to both configure and estimate ARX
models:
% Using ARX method
3-60