Importing a Model in FMU Format

You can import an FMU (Functional Mock-up Unit) into the Dymola Behavior Modeling app. If you have imported a co-simulation FMU, you can specify the macro step size of the instantiated FMU.

Important: The attribute nominal for scalar variables is not supported when importing FMU models with Model Exchange.
Notes:
  • Unless otherwise stated, features are available for both FMI version 1.0 and FMI version 2.0.
  • String parameters are supported, but not string variables.
  • Online tunable parameters are supported in FMI version 2.0 (such parameters are not defined in FMI version 1.0).
  • Unit conversion is supported in FMI version 2.0. Units are automatically converted to base units, according to the FMI standard, for inputs, outputs, and parameters in imported FMUs.
Tips:
  • You can specify start values for FMI Model Exchange, to specify input start values before initialization. This can be useful when wanting to avoid, for example, division by zero when initializing.
  • When importing FMUs with many inputs or outputs, the connectors are stacked. The minimum number when stacking occurs can be changed by a preference Minimal number to activate stacking of connectors. The default is 10 connectors. You reach these preferences from Me > Preferences > App Preferences > 3D Modeling > Systems > Behavior Modeling, the FMI tab. For more information about FMI preferences, see FMI. For connection of stacked connectors, see Connecting Stacked Connectors.
  • You can instantiate the same imported FMU several times in the same model.
  • You can import FMUs of FMI version 1.0 and 2.0 to the same model.
  • When importing FMUs from other vendors, the parameter fmi_resourceLocation in the FMI tab of the parameter dialog of the FMU might be required to specify the location of external resources. (For FMI version 1.0 Co-simulation the parameter name is fmi_fmuLocation.) By default the parameter displays the location where the FMU is unpacked, which is usually the location of external resources (dlls, tables, etc.) as well.
  • When you import an FMU, the initial values of the parameters are put in a separate tab Initial in the parameter dialog of the FMU. As an example, if you only have initial values for a state, the General tab may be empty, but the initial values are listed in the Initial tab.
  • Information from the model description (modelDescription.xml) of an imported FMU is displayed in the information layer of the imported FMU.

This task shows you how to:

Before you begin: There is no need for a specific license to import an FMU, but the FMU itself might demand a license corresponding to the system used to create the FMU.
See Also
About Interfacing Other Simulation Environments

Import by a Command

You can import a model in an FMU format using a command.

Notes:
  • Except from selecting the FMU itself, the selections you can do corresponds almost to what you can select by preferences. The differences are:
    • When importing an FMU, you can also select to specify exactly what variables you want to include in the FMU.
    • When importing an FMU, you can also select if to be prompted before replacing an existing Modelica model when importing the FMU.
    • The minimal number to activate stacked connectors can only be specified in this preference dialog.
  • For the preferences dialog here, and the corresponding settings in the dialog when importing an FMU, if you change any preference or setting, it is changed in both dialogs.
  • The settings corresponding to the preferences are kept between sessions.
  • You can select preferences from Me > Preferences > App Preferences > 3D Modeling > Systems > Behavior Modeling, the FMI tab. See FMI.

  1. From the Behavior Authoring section of the action bar, click Import FMU .

    Tip: You can also drag the FMU file from, for example, the file browser and drop it in the work area. If a model is selected from the Package Browser, the FMU is instantiated in the top level of the corresponding library of that model.

    The Import FMU dialog box appears.
  2. Browse to select your FMU file and click Open.
    The Import FMU dialog box appears. The name of the selected FMU is prefilled in the first field.
  3. Optional: To select another FMU, click Browse and browse for another FMU.
  4. Select Preferred type as any of:
    • Model exchange
    • Co-simulation
  5. Select what options to activate:
    1. To have a warning before replacing an existing Modelica model, activate Prompt before replacing an existing Modelica model.
    2. To include a file containing the variable names in the FMU, activate Translate value reference to variable name

      This is useful for debugging, but might affect the performance. With this preference selected, value references are mapped to variable names in the FMU log messages.

    3. To present the variables of the imported FMU in a hierarchical structure using records declarations, activate Structured declaration of variables.

      This is useful when you, for example, want to change parameter values in the variable browser after a simulation.

      Note: To be able to use this option, the attribute variableNamingConvention in the model description file of the FMU to be imported must be specified to variableNamingConvention="structured".

  6. To select the target package to import the FMU to, you can do any of the following:
    • To select any previously visited packages, click the arrow and select a package.
    • To browse for a package, click Select Package.
      Note: You have a search field in top of the dialog box that appears when you browse for a package.
    • Enter the package name in the box.
    The selected package appears in the field.
    Note: If you don´t select any package, the FMU is imported to the root level of the Package Browser.
  7. To select what variables to expose in the imported FMU, do any of the following:
    • To expose all variables in the imported FMU, select All variables, then go to to Step 9.
    • To expose only parameters, inputs, and outputs, select Black box (parameters, inputs, outputs), then go to Step 9.
    • To specify in detail what variables to expose, click These variables. See next step for selection.
  8. To specify what variables to expose when you have selected These variables in the previous step, click Select to display a dialog for selection.

    In the dialog, by default, all variables are selected to be exposed.

    1. In the left part of the dialog, select the variables to hide.

      You can:

      • Search for variables by typing in the first field.
      • Expand and collapse nodes in the tree individually, or all by clicking Expand All or Collapse All.
      • Multiselect variables individually, or all by clicking Select All or Select None.

    2. Click Hide to hide the selected variables.

      Tip: To instead work with what variables to expose, do the following:
      1. In the left part of the dialog, click Select All.
      2. Click Hide.
      You can now work with what variables to expose in the same way as working with what variables to hide.

    3. When you have finalized the selection, click OK.
      The variables to expose are listed in the field under These variables in the previous dialog box.
      Tip: You can use this result if you want to use scripting, right-click the field, select Select All, then right-click the field again and select Copy. You now have the list of exposed variables in the clipboard.
  9. Click OK to import your .fmu file containing the corresponding resources within the Dymola Behavior Modeling app.
    A progress bar appears.
    Note: As the .fmu file is checked before import, it must be correct for a successful import.

    The Message Reporting window appears to let you know the import result.

  10. Save.

Import by Scripting

You can import a model in FMU format by scripting.

Note: The binary library files from any previous import are replaced when calling the below scripting function. For this reason, translation of previously imported FMU models are not guaranteed to work any longer (in the unlikely event of a name clash).

Before you begin: Some preferences apply also when using scripting (the rest can be specified in the scripting function):
  • Translate value reference to variable name
  • Structured declaration of variables.
These preferences can be changed from Me > Preferences > App Preferences > 3D Modeling > Systems > Behavior Modeling, the FMI tab. See FMI. The preferences are kept between sessions.
  1. Open the Modelica Scripting window, see Create and Execute a Script.
  2. Use the scripting function importFMU(fileName, includeAllVariables, integrate, promptReplacement, packageName, includeVariables).
    1. Set fileName to the name of the FMU file to be imported, including the path, e. g. "E:/Import/MyFMUFile.fmu"
    2. Set includeAllVariables to false if only inputs, outputs, and parameters are to be exposed (black-box import).

      By default, this parameter is true, exposing all variables.

      Tip: Setting this parameter to false reduces the size of the mo file. This is recommended for large models.

      Important: Instead of using this parameter, you can specify in detail what variables to be exposed by using the variable includeVariables - see below.

    3. Set integrate to false if the co-simulation part of the FMU is to be used.

      By default, this parameter is true, meaning that the model exchange part of the FMU is used.

      Note: This parameter is only relevant for FMU models supporting both model exchange and co-simulation. Otherwise this parameter is ignored.

    4. Set promptReplacement to true if you want to be prompted before replacement of any existing Modelica model from a previous import.

      Tip: Having no prompting is useful when you want to repeatedly import FMUs using scripting.
      By default, this parameter is false.

    5. Set packageName to the name of the package where the FMU is to be inserted, for example "MyLib".

      Important: The package must be open in the Package Browser.

      By default, this parameter is an empty string, meaning that the FMU is inserted in the top level of the Package Browser.

    6. To specify in detail what variables are to be exposed, you can enter them using the parameter includeVariables.

      By default, this parameter is an empty array, meaning that the parameter includeAllVariables specifies what variables to expose (see this parameter above).

      Tip: One convenient way to create the array to be inserted is to use the command for FMU import. Specify what variables you want to expose using this command, and then copy the resulting text string and use that. See previous task, Step 8.

  3. Execute the script, see Create and Execute a Script.
    When the script is executed:
    • A progress bar appears.
    • The Message Reporting window appears to let you know the import result.
    • If the import is successful, the .fmu file containing the corresponding resources is imported to the Dymola Behavior Modeling app.
    Note: As the .fmu file is checked before import, it must be correct for a successful import.
  4. Save.

Set the Macro Step Size of an Imported and Instantiated Co-simulation FMU

If you have imported a co-simulation FMU, you can specify the macro step size of the instantiated FMU.

Before you begin: Import and instantiate a co-simulation FMU.
  1. Right-click the FMU in the diagram or Component Browser and select Edit Component Parameters.
  2. Select the FMI tab.
  3. Type the value in the fmi_CommunicationStepSize: box.

    The default value is (fmi_StopTime - fmi_Starttime)/500.

  4. Click OK.