User`s guide

Identifying Nonlinear ARX Models
• In the Regressors tab, change the input delay of the input signals.
To gain insight into possible input delay values, click Infer Input
Delay. This action opens the Infer Input Delay dialog box.
• In the Regressors tab, change the number of terms to include in the
nonlinear block.
• In the Regressors tab, click Edit Regressors to select which regressors
are included in the nonlinear block. This a ction o pens the Model
Regressors dialog box. You can also use this d ialog box to create custom
regressors.
• In the Model Properties tab, select and configure the nonlinearity
estimator, and choose whether to include the linear block. To use all
standard and custom regressors in the linear block only, you can exclude
the nonlinear block b y choosing
None.
For more information about the available options, click Help in the
Nonlinear Models dialog box to open the GUI help.
6 Click Estim ate to add this model to the M odel Board in the System
Identification Tool GUI.
The Estimation tab displays the estimation progress and results.
7 To plot the response of this m odel, select the appropriate check box in
the Model Views area of the System Identification Tool GUI. If you get
an inaccurate fit, try estimating a new model with different orders or
nonlinearity estimator. For more information about validating models, s ee
Chapter 8, “Model Analysis”.
8 For further analysis, export the model to the MATLAB workspace by
dragging it to the To Workspace rectangle in the System Identification
Tool GUI.
How to Estimate Nonlinear ARX Models at the
Command Line
• “General nlarx S yn tax ” on page 4-12
• “Example – Using nlarx to Estimate Nonli near AR X Mod el s” on page 4 -13
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