Viewing Model Parameters

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Viewing Model Parameter Values Viewing Parameter Uncertainties

Viewing Model Parameter Values

You can view the numerical parameter values for each estimated model.

You must have already estimated the models, as described in Estimating Accurate Linear Models.

If you have not performed this step, click here to complete it.

To view the parameter values of the model amx3322, right-click the model icon in the System Identification Tool GUI. The Data/model Info dialog box opens.

The noneditable area of the Data/model Info dialog box lists the following parameter values:

A(q) = 1 - 1.508q^-1 + 0.7291q^-2 - 0.1219q^-3
B(q) = 0.004257q^-2 + 0.06201q^-3 + 0.02643q^-4 
C(q) = 1 - 0.5835q^-1 + 0.2588q^-2               

These parameter values correspond to the following difference equation for your system:

Note   The coefficient of u(t-2) is not significantly different from zero. This lack of difference explains why delay values of both 2 and 3 give good results.

Parameter values appear in the following format:

The parameters appear in the ARMAX model structure, as follows:

which corresponds to this general difference equation:

y(t) represents the output at time t, u(t) represents the input at time t, n_a is the number of poles for the dynamic model, n_b is the number of zeros plus 1, n_c is the number of poles for the disturbance model, n_k is the number of samples before the input affects output of the system (called the delay or dead time of the model), and e(t) is the white-noise disturbance.

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Viewing Parameter Uncertainties

You can view parameter uncertainties of estimated models.

You must have already estimated the models, as described in Estimating Accurate Linear Models.

If you have not performed this step, click here to complete it. To view the parameter values of the model amx3322, right-click the model icon in the System Identification Tool GUI. The Data/model Info dialog box opens.

To view parameter uncertainties, click Present in the Data/model Info dialog box, and view the model information in the MATLAB Command Window.

A(q) = 1 - 1.508(+-0.05919)q^-1
       + 0.7291(+-0.08734)q^-2
       - 0.1219 (+-0.03424)q^-3
B(q) = 0.004257(+-0.001563)q^-2
       + 0.06201(+-0.002409)q^-3
       + 0.02643(+-0.005633)q^-4 
C(q) = 1 - 0.5835(+-0.07189)q^-1
         + 0.2588(+-0.05253)q^-2

The 1-standard-deviation uncertainty for the model parameters is in parentheses next to each parameter value.

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Estimating Accurate Linear Models

Exporting the Model to the MATLAB Workspace

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