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Analyzing MIMO Models

Overview of Analyzing MIMO Models

If you import a MIMO system, or an LTI array containing multiple identified linear models, you can use special features of the right-click menu to group the response plots by input/output (I/O) pairs, or select individual plots for display. For example, generate a random 3-input, 3-output MIMO system and then randomly sample it 10 times. Plot the step response for all the models.

sys_mimo=rsample(idss(rss(3,3,3)),10);
step(sys_mimo);

sys_mimo is an array of ten 3-input, 3-output systems.

A set of 9 plots appears, one from each input to each output, for the ten model samples.

Array Selector

If you plot an identified linear model array, Array Selector appears as an option in the right-click menu. Selecting this option opens the Model Selector for LTI Arrays, shown below.

You can use this window to include or exclude models within the LTI array using various criteria.

Arrays

Select the LTI array for model selection using the Arrays list.

Selection Criteria

There are two selection criteria. The default, Index into Dimensions, allows you to include or exclude specified indices of the LTI Array. Select systems from the Selection Criterion Setup and specify whether to show or hide the systems using the pull-down menu below the Setup lists.

The second criterion is Bound on Characteristics. Selecting this options causes the Model Selector to reconfigure. The reconfigured window is shown below

Use this option to select systems for inclusion or exclusion in your response plot based on their time response characteristics. The panel directly above the buttons describes how to set the inclusion or exclusion criteria based on which selection criteria you select from the reconfigured Selection Criteria Setup panel.

I/O Grouping for MIMO Models

You can group the plots by inputs, by outputs, or both by selecting I/O Grouping and then Inputs, Outputs, or All, respectively, from the right-click menu.

For example, if you select Outputs, the step plot reconfigures into 3 plots, one for each input.

Selecting None returns to the default configuration, where all I/O pairs are displayed individually.

Selecting I/O Pairs

Another way to organize MIMO system information is to choose I/O Selector from the right-click menu, which opens the I/O Selector window.

This window automatically configures to the number of I/O pairs in your MIMO system. You can select:

  • Any individual plot (only one at a time) by clicking on a button

  • Any row or column by clicking on Y(*) or U(*)

  • All of the plots by clicking [all]

Using these options, you can inspect individual I/O pairs, or look at particular I/O channels in detail.

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