Evaluate Design Requirements

This topic shows how to evaluate your design requirements in the Sensitivity Analysis tool. After you generate values for your parameter set and specify design requirements, you can evaluate your design requirements (cost function) at each sample of parameter values in your parameter set.

The generated parameter set, the corresponding parameter set table, and specified requirements are displayed in the tool.

To evaluate the design requirements:

  1. Select the parameter set to use for evaluation.

    If you have multiple parameter sets defined, select the parameter set to use from the Parameter Set to Evaluate drop-down list.

  2. Select the requirements you want to evaluate.

    If you have multiple requirements defined, they are all selected by default for evaluation. To exclude a requirement from evaluation, click Select for Evaluation.

  3. Specify evaluation options.

    Click Options. In the Evaluation Options dialog box, in the General Options tab, specify options related to evaluation progress and results. If you have Parallel Computing Toolbox™, you can specify options for parallel computing in the Parallel Options tab. If you have Simulink® Control Design™ software, you can specify options for linearizing your model in the Linearization Options tab. For details about these options, click Help.

  4. Speed up successive evaluations of design requirements that require the same logged signals and parameter values.

    Click Store Intermediate Data. For more information, see Store Intermediate Data in the Tool.

  5. Evaluate the design requirements for each sample in your parameter set.

    Click Evaluate Model. The cost function associated with your design requirement is evaluated using each sample in your parameter set. A sample corresponds to a row of values in the parameter set table.

The tool generates a evaluation result scatter plot. The plot updates to display the evaluated cost function value as a function of each parameter in the parameter set. The last column of subplots displays histograms of the probability distribution of the evaluated cost function values.

When the evaluation is complete, the tool displays the evaluated requirement (normalized cost function value) and the corresponding parameter values in the Evaluation Result table. The tool also creates a new variable with this information in the Results area.

For requirements that involve a bound, a positive requirement value indicates that your requirement was violated, while a negative value indicates that the requirement was satisfied for that sample of parameter values. The parameter sample (row) corresponding to the least requirement value comes closest to satisfying your requirement.

You can employ the evaluation results to configure estimation or optimization of your parameters. For more information, see Use Sensitivity Analysis to Configure Estimation and Optimization.

The tool displays the final scatter plots and probability distribution histogram. The number of data points in each scatter plot equals the number of samples (rows) in the parameter set table. Use this plot to visually analyze the relation between parameters and requirements. For example, in this case, the SignalMatching requirement looks monotonically related to the Gain parameter. To learn more about the plot, see Interact with Plots in the Sensitivity Analysis Tool.

You can make a contour plot of the evaluated results. To do so, select the evaluated result in the Results area of the tool, and choose a contour plot in the Plots tab of the tool.

 The contour plot shows that the requirement does not vary systematically as a function of Delay, but it does as a function of Gain.

You can also quantify the relation between parameters and requirements. For more information, see Analyze Relation Between Parameters and Design Requirements.

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