Applying Integrated Linear Systems Analysis Tools

You can apply integrated linear system analysis tools on a model.

This task shows you how to:

Before you begin:
Notes:
  • These tools are shortcuts to functions in the library Modelica_LinearSystems2; more tools are available in that library. To use other functions, use the general functions call, see Calling Functions.
  • You can specify locations where to look for the library if it is not found by default when applying a linearize command from the action bar. You specify the locations from Me > Preferences > App Preferences > 3D Modeling > Systems Modeling and Execution > Dymola Behavior Modeling , the Library tab, the preference Additional 3DXML´s location. For more information, see Libraries.
See Also
About Postprocessing with Integrated Linear Systems Analysis Tools

Linearize

You can linearize a model and return the linearized model as StateSpace object.

  1. From the Behavior Tools section of the action bar, click Linearize .

    Tip: You can also access this command from the Simulation section of the action bar.

    A dialog box for the corresponding function call in Modelica_LinearSystems2 is displayed.
  2. If the wanted model is not selected, click Edit .
    A Select model dialog box is displayed; browse for the model by expanding the trees, select the wanted model and click OK.
    Note: When a new model is selected, it is translated after the selection.
  3. Optional: You can enter values of model parameters for the linearization:
    1. Click modelParam in the left pane of the dialog box in the first figure above.
      The modelParam tab is displayed:
    2. Click select in the lower right corner of the dialog box.
      A select dialog box is displayed.
    3. Browse for, and select, components.
    4. Click OK to validate selection and close the select dialog box, or Cancel to close the dialog box without any changes.
    5. To change the values of selected model parameters, click the corresponding Value boxes and change the values.

      Tip: To reset the values, click select to reopen the select dialog box and select the Reset from file: Value option, and then click OK.

  4. Optional: You can change the simulation setup if you start the linearization after the initial time:
    1. Click simulationSetup in the left pane of the dialog box.
      The simulationSetup tab is displayed:
    2. Deselect linearizeAtInitial.
      You can now select the following:
      • t_start (simulation start time).
      • t_linearize (start time of linearization).
      • method (integration method to be used between t_start and t_linearize).
      • tolerance (relative error tolerance to be used between t_start and t_linearize).
      • fixedStepSize (step size for fixed step integrators, to be used between t_start and t_linearize).
  5. Select OK or Execute to execute the function. You could also select:
    • Info to display a Help window and display information about the function.
    • Copy Call to copy the function call with the values. This can be used for further scripting.
    • Close to exit the dialog box without calling the function.
    The following is performed:
    • The function call is executed.
    • The Modelica Scripting window displays the function call and the result. For more information, see The Modelica Scripting Window.
    • Information about the execution is displayed in the Messages Reporting window, including where the file is located in which the simulation results are stored. See Messages Reporting Window for more information about this window.

Compute (Zeros and) Poles

You can linearize a model and plot the (zeros and) poles of the linearized model.

  1. From the Behavior Tools section of the action bar, click Compute poles , or Compute zeros and poles , respectively.

    Tip: You can also access this command from the Simulation section of the action bar.

    A dialog box for the corresponding function call in Modelica_LinearSystems2 is displayed.
  2. If the model to be used is not selected, see step 2 in the first task above.
  3. If the required model is not selected, click Edit .
  4. Optional: You can enter values of model parameters for the linearization; see step 3 in the first task above.
  5. Optional: You can change the simulation setup if you start the linearization after the initial time; see step 4 in the first task above.
  6. Select OK or Execute to execute the function. You could also select:
    • Info to display a Help window and display information about the function.
    • Copy Call to copy the function call with the values. This can be used for further scripting.
    • Close to exit the dialog box without calling the function.
    The following is performed:
    • The function call is executed.
    • The Modelica Scripting window displays the function call and the result. For more information, see The Modelica Scripting Window.
    • The poles (and zeros if the corresponding function is selected) are presented in a plotter.
    • Information about the execution is displayed in the Messages Reporting window, including where the file is located in which the simulation results are stored. See Messages Reporting Window for more information about this window.

Generate a Bode Plot

You can linearize a model and plot the Bode plot from all inputs to all outputs of the linearized model.

Important: You must have at least one input to the system to be able to create Bode plot.

  1. From the Behavior Tools section of the action bar, click Bode plot .

    Tip: You can also access this command from the Simulation section of the action bar.

    A dialog box for the corresponding function call in Modelica_LinearSystems2 is displayed.
  2. If the model to be used is not selected, see step 2 in the first task above.
  3. Optional: You can enter values of model parameters for the linearization; see step 3 in the first task above.
  4. Optional: You can change the simulation setup if you start the linearization after the initial time; see step 4 in the first task above.
  5. Select OK or Execute to execute the function. You could also select:
    • Info to display a Help window and display information about the function.
    • Copy Call to copy the function call with the values. This can be used for further scripting.
    • Close to exit the dialog box without calling the function.
    The following is performed:
    • The function call is executed.
    • The Modelica Scripting window displays the function call and the result. For more information, see The Modelica Scripting Window.
    • The Bode diagrams are presented in a plotter.
    • Information about the execution is displayed in the Messages Reporting window, including where the file is located in which the simulation results are stored. See Messages Reporting Window for more information about this window.

Perform a Full Analysis

You can linearize a model and perform all available linear analysis operations.

  1. From the Behavior Tools section of the action bar, click Perform a full analysis .

    Tip: You can also access this command from the Simulation section of the action bar.

    A dialog box for the corresponding function call in Modelica_LinearSystems2 is displayed.
  2. If the model to be used is not selected, see step 2 in the first task above.
  3. Optional: You can enter values of model parameters for the linearization; see step 3 in the first task above.
  4. Optional: You can change the simulation setup if you start the linearization after the initial time; see step 4 in the first task above.
  5. Select OK or Execute to execute the function. You could also select:
    • Info to display a Help window and display information about the function.
    • Copy Call to copy the function call with the values. This can be used for further scripting.
    • Close to exit the dialog box without calling the function.
    The following is performed:
    • The function call is executed.
    • The Modelica Scripting window displays the function call and the result. For more information, see The Modelica Scripting Window.
    • The poles and zeros are presented in a plotter.
    • Information about the execution is displayed in the Messages Reporting window, including where the file is located in which the simulation results are stored. See Messages Reporting Window for more information about this window.

Plot Root Locus Analysis

You can compute and plot the root locus of one parameter of a model (= eigenvalues of the model that is linearized for every parameter value).

  1. From the Behavior Tools section of the action bar, click Plot root locus analysis .

    Tip: You can also access this command from the Simulation section of the action bar.

    A dialog box for the corresponding function call in Modelica_LinearSystems2 is displayed.
  2. If the model to be used is not selected, see step 2 in the first task above.
  3. Enter model parameter to be varied and values for other parameters:
    1. Click modelParam in the left pane of the dialog box.
      The modelParam tab is displayed.
    2. Click select.
      A select dialog box is displayed.
    3. Browse for, and select, the parameter to be varied.

      Important: Select only one parameter.

    4. Click OK to validate selection and close dialog box, or Cancel to close the dialog box without any changes.
    5. You can change the value of the selected model parameter; by clicking the corresponding grid, Value, Min, Max, and nPoints boxes and changing the values.

      Note: You can reset the values by opening again the select dialog box and ticking Reset from file: Value in that dialog box, and then clicking OK.

  4. Optional: You can change the simulation setup if you start the linearization after the initial time; see step 4 in the first task above.
  5. Optional: You can change the properties of the root locus diagram.
    1. Click diagram in the left pane of the window.
      The diagram tab is displayed.
    2. Change the properties you want; for example adding a heading, changing color of lines.
  6. Optional: You can change the properties of the device where the figure is shown.
    1. Click device in the left pane of the window.
      The diagram tab is displayed.
    2. Change the properties you want; for example setting the resolution of the image.
  7. Select OK or Execute to execute the function. You could also select:
    • Info to display a Help window and display information about the function.
    • Copy Call to copy the function call with the values. This can be used for further scripting.
    • Close to exit the dialog box without calling the function.
    The following is performed:
    • The function call is executed.
    • The Modelica Scripting window displays the function call and the result. For more information, see The Modelica Scripting Window.
    • The root locus diagram is presented in a plotter.
    • Information about the execution is displayed in the Messages Reporting window, including where the file is located in which the simulation results are stored. See Messages Reporting Window for more information about this window.