Specify Portion of Model to Linearize in Simulink Model

To specify the portion of the model to linearize, you can define and save linear analysis points directly in your Simulink® model. Analysis points represent linearization inputs, outputs, and loop openings for your model.

Alternatively, to specify analysis points without changing your model, you can define analysis points:

Specify Analysis Points

To specify analysis points directly in your Simulink model:

  1. Right-click the signal you want to define as an analysis point, and hover the cursor over Linear Analysis Points.

  2. Under Linear Analysis Points, select the type of analysis point you want to define.

    • Input Perturbation — Specifies an additive input to a signal.

    • Output Measurement — Takes a measurement at a signal.

    • Loop Break — Specifies a loop opening.

    • Open-Loop Input — Specifies a loop break followed by an input perturbation.

    • Open-Loop Output — Specifies an output measurement followed by a loop break.

    • Loop Transfer — Specifies an output measurement before a loop break followed by an input perturbation.

    • Sensitivity — Specifies an input perturbation followed by an output measurement.

    • Complementary Sensitivity — Specifies an output measurement followed by an input perturbation.

    For more information on the different types of analysis points, see Specify Portion of Model to Linearize.

    When you specify analysis points, the software adds annotations to your model indicating the linear analysis point type.

  3. Repeat steps 1 and 2 for all signals you want to define as analysis points.

For each linear analysis point that you specify, the software adds an annotation to your model indicating the analysis point type.

Select Bus Elements as Analysis Points

This example shows how to select individual elements in a bus signal as analysis points.

  1. Open Simulink model.

    sys = 'scdbusselection';

  2. Specify a bus signal as a linear analysis point.

    In the Simulink model window, right-click a bus signal, such as the OUTPUTBUS signal, and select Linear Analysis Points > Select Bus Element.

    In the Select Linearization Points in the Bus dialog box, in the Bus Hierarchy section, expand the limits bus, and select upper_saturation_limit. limits is a nested bus within the OUTPUTBUS signal.


    To filter bus elements by name within a large bus, you can enter search text in the Filter by name box. The name match is case-sensitive. Also, you can enter a MATLAB® regular expression (MATLAB).

    To modify the filtering options, click next to the Filter by name box.

     Filtering Options

    To add the selected signal to the Linearization Inputs/Outputs section, click Add. By default, the signal is configured as an Input Perturbation analysis point.

    You can change the analysis point type using the Configuration drop-down list. For example, to specify a linearization output point, select Output Measurement.

  3. To add additional analysis points from within the same bus signal, repeat step 2.

    To remove an analysis point, select the signal in the Linearization Inputs/Outputs section, and click Remove.

    Once you have defined all of the required analysis points for that bus, click OK.

  4. To specify analysis points for another bus signal, repeat steps 2 and 3.

  5. To view linear analysis point indicators in the Simulink model, in the model window, select Display > Signals & Ports > Linearization Indicators.

    The software adds graphical annotations to the bus signals indicating the type of analysis points specified. For example, if you specify a linearization input in the COUNTERBUS signal and a linearization output in the OUTPUTBUS signal, the software adds the corresponding annotations to the signals.

    You can specify different analysis point types for multiple elements in the same bus. In this case, the software adds the annotation to the signal.

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