Sensitivity Analysis

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Sensitivity Analysis

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Using the Tolerance Analysis option of the Multiple Run Wizard, you can analyze the effects of variation of parameters / initial values on the performance of your model. Three methods of Tolerance analysis are supported in the Multiple Run Wizard. One of these methods is Sensitivity analysis.

 

Sensitivity analysis starts with a simulation run with nominal parameter values. After the run a given result is monitored (r). Then, one by one, each parameter (pi) is changed with a given percentage (to pi + dpi) and a simulation run is performed. After the simulation run the changed result is monitored (r + dri). After all the runs, the results are displayed as sensitivities, where sensitivity is defined as the change in result divided by the change in parameter:

 

Si = dri / dpi

 

A large sensitivity means that the result is highly dependant of the parameter value. This can be used for optimization (change the parameter value) or design (change the design to make it less dependant of the parameter).

Parameters / Initial Values

1.From the Tools menu select the Time Domain Toolbox and then Sensitivity Analysis.

A window opens asking you which parameters / initial values should be changed for the Sensitivity analysis:

Sensitivity1

3.Add the parameters / initial values of your choice:
4.Click the Next button.

Result

A window opens asking you which result should be monitored for the sensitivity:

Sensitivity2

5.Enter the result here using the various options of the window.
6.Click the Next button.

Run options

A window opens asking some simulation run options:

Sensitivity3

7.Select the desired run options and click the Next button.

A window opens with a summary of the chosen options. If your are not satisfied you can use the Back button to go to a previous window and change settings.

8.Click the Finish button to close the Multiple Run Wizard.
9.From the Simulation menu click the Multiple Run command to perform the Sensitivity Analysis.

Sensitivity Analysis Results

After simulation has been done, a Sensitivity Analysis Results window will open, showing the sensitivities:

Sensitivity4

You can select the following items:

Multiple Run Values: Choose this button to open the list that shows the output of the various runs performed during the sensitivity analysis.
Close: Close the Sensitivity Analysis Results Window.

 

You can always re-open the Multiple Run Results window, by selecting the Multiple Run Results command of the View Menu.

10.By choosing the Multiple Run Values button, a new window is opened, showing output of the various runs performed during the sensitivity analysis:

In the Results list of this window the subsequent runs are shown and the corresponding sensitivities.

Sensitivity5

You can select the following items:

Set Values: Choose the values of the selected run, as new parameter values of your model.
Create Datafile: Use this button to store the values of the selected variables on file. Use the control-key and shift-key to make multiple selections.