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Use Sensitivity Analysis to Configure Estimation and Optimization

This topic shows how to use the results generated in the Sensitivity Analysis tool to configure parameter estimation or response optimization.

You can use sensitivity analysis to evaluate how the parameters of a Simulink® model influence the model output or model design requirements. You first generate samples of the parameters, and then define a cost function by creating a design requirement on the model signals. For more information see, Generate Parameter Samples for Sensitivity Analysis, Specify Time-Domain Requirements, and Specify Frequency-Domain Requirements. You then evaluate the requirement (cost function) for each sample. You can use the evaluated results to configure parameter estimation or response optimization in the following ways:

  1. Analyze the relationship between the parameters and the evaluated requirement values, and rank parameters in order of influence. For more information, see Analyze Relation Between Parameters and Design Requirements. You can then choose to estimate or optimize the more influential parameters.

  2. Obtain initial guesses for parameter values for estimation or optimization.

    After you evaluate the requirements in the Sensitivity Analysis tool, the evaluated requirement (cost function value) and the corresponding parameter values are displayed in the Evaluation Result table of the tool. A new variable, EvalResults, with this information is created in the Results area of the tool. For example, the table below lists the evaluated signal matching requirement and corresponding values for the parameters Gain, Delay, Tc, and Tp of the model, sdoVOR.

    To extract parameter values to use as an initial guess during estimation or optimization:

    1. Sort the evaluated cost function values in ascending order by clicking the evaluated requirement column.

    2. To choose the parameter values that minimize the cost function, right-click corresponding row, and select Extract Parameter Values.

      A new variable, ParamValues, is created in the Results area of the tool.

    3. When exporting to a Parameter Estimation or Response Optimization tool session, choose this variable to specify the initial guess for parameters.

  3. To test the robustness of your design during optimization in the Response Optimization tool, specify the values for uncertain parameters. For more information, see Optimizing Parameters for Robustness.

    You can specify the values for uncertain parameters using all the parameter values in EvalResults. You can also choose a subset of the parameter values:

    1. Select the relevant rows of parameter values in the Evaluation Result table of the tool.

    2. Right-click, and select Create new evaluation result. A new variable is created in the Results area of the tool.

    3. When exporting to a Response Optimization tool session, choose this variable to specify the uncertain variables.

Export Sensitivity Analysis Results

You can export results from Sensitivity Analysis tool to the Parameter Estimation and Response Optimization tools. To do so, in the Sensitivity Analysis tool, click Optimize. In the drop-down menu, choose the tool to export to.

Alternatively, if you have an open Parameter Estimation or Response Optimization tool session, in these tools, click Sensitivity Analysis. In the drop-down menu, choose Import from Open Session or Import from Session file. The latter option loads results from a previously saved Sensitivity Analysis tool session.

Note

  • Only signal matching requirements are exported from Sensitivity Analysis to a Parameter Estimation tool session. In the Parameter Estimation tool, they are referred to as experiments.

  • Only requirements other than signal matching requirements are exported from Sensitivity Analysis to a Response Optimization tool session.

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