Testing a Unique Chart Configuration

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Goal of the Tutorial Defining the SimState Loading the SimState and Modifying Values Testing the Modified SimState

Goal of the Tutorial

Suppose that you want to test the response of the sf_car model to a sudden change in value for gear.

This model simulates for 30 seconds, but you want to see what happens when the value of gear changes at t = 10. You can simulate the model, save the SimState at t = 10, load and modify the SimState, and then simulate again between t = 10 and 20.

Step	Task	Reference
1	Define the SimState for your chart.	Defining the SimState
2	Load the SimState and modify values.	Loading the SimState and Modifying Values
3	Test the modified SimState by running the model.	Testing the Modified SimState

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Defining the SimState

1. Open the model.

   Type sf_car at the command prompt.

2. Enable saving of a SimState.

   1. Open the Configuration Parameters dialog box and go to the Data Import/Export pane.

   2. Select the Final states check box.

   3. Enter a name, such as sf_car_ctx01.

      You can choose any alphanumeric string for the name.

   4. Select the Save complete SimState in final state check box.

   5. Click Apply.

    Programmatic equivalent

   You can programmatically enable saving of a SimState:

   set_param('sf_car','SaveFinalState','on', ...
   'FinalStateName', ['sf_car_ctx01'], ...
   'SaveCompleteFinalSimState','on');

   For details about setting model parameters, see set_param in the Simulink Reference.

3. Define the start and stop times for this simulation segment.

   1. In the Configuration Parameters dialog box, go to the Solver pane.

   2. For Start time, enter 0.

   3. For Stop time, enter 10.

   4. Click OK.

    Programmatic equivalent

   You can programmatically set the start and stop times:

   set_param('sf_car','StartTime','0', ...
   'StopTime','10');

4. Start simulation.

   When you simulate the model, you save the complete simulation state at t = 10 in the variable sf_car_ctx01 in the MATLAB base workspace.

   At t = 10, the engine is operating at a steady-state value of 2500 RPM.

   

5. Disable saving of a SimState.

   This step prevents you from overwriting the SimState you saved in the previous step.

   1. Open the Configuration Parameters dialog box and go to the Data Import/Export pane.

   2. Clear the Save complete SimState in final state check box.

   3. Clear the Final states check box.

   4. Click OK.

    Programmatic equivalent

   You can programmatically disable saving of a SimState:

   set_param('sf_car','SaveCompleteFinalSimState','off', ...
   'SaveFinalState','off');

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Loading the SimState and Modifying Values

1. Enable loading of a SimState.

   1. Open the Configuration Parameters dialog box and go to the Data Import/Export pane.

   2. Select the Initial state check box.

   3. Enter the variable that contains the SimState of your chart: sf_car_ctx01.

   4. Click OK.

    Programmatic equivalent

   You can programmatically enable loading of a SimState:

   set_param('sf_car','LoadInitialState','on', ...
   'InitialState', ['sf_car_ctx01']);

2. Define an object handle for the SimState values of the shift_logic chart.

   At the command prompt, type:

   blockpath = 'sf_car/shift_logic';
   c = sf_car_ctx01.getBlockSimState(blockpath);

   Tip   If the chart appears highlighted in the model window, you can specify the block path using gcb: c = sf_car_ctx01.getBlockSimState(gcb);

    What does the getBlockSimState method do?

   The getBlockSimState method:

   • Makes a copy of the SimState of your chart, which is stored in the final state data of the model.

   • Provides a root-level handle or reference to the copy of the SimState, which is a hierarchical tree of graphical and nongraphical chart objects.

     Each node in this tree is also a handle to a state, data, or other chart object.

   Note   Because the entire tree consists of object handles, the following assignment statements do not work: stateCopy = c.state dataCopy = c.data simstateCopy = c These assignments create copies of the object handles, not SimState values. The only way to copy SimState values is to use the clone method. For details, see Methods for Interacting with the SimState of a Chart and Rules for Using the SimState of a Chart.

3. Look at the contents of the SimState.

   c = 
   
     Block:    "shift_logic"    (handle)    (active)
     Path:     sf_car/shift_logic
   
     Contains:
   
       + gear_state         "State (AND)"          (active)
       + selection_state    "State (AND)"          (active)
         gear               "Block output data"    double [1, 1]
         down_th            "Local scope data"     double [1, 1]
         up_th              "Local scope data"     double [1, 1]

   The SimState of your chart contains a list of states and data in hierarchical order.

4. Highlight the states that are active in your chart at t = 10.

   At the command prompt, type:

   c.highlightActiveStates;

   In the chart, all active states appear highlighted.

   

   To highlight active states automatically at the end of a simulation, enable chart animation and select Maintain Highlighting in the debugger. For details, see Animating Stateflow Charts.

   Tip   To check if a single state is active, you can use the isActive method. For example, type: c.gear_state.second.isActive This command returns true (1) when a state is active and false (0) otherwise. For information on other methods, see Methods for Interacting with the SimState of a Chart.

5. Change the active substate of selection_state to downshifting.

   Use this command:

   c.selection_state.downshifting.setActive;

   The newly active substate appears highlighted in the chart.

   

6. Change the value of output data gear.

   When you type c.gear at the command prompt, you see a list of data properties similar to this:

   >> c.gear
   
   ans = 
   
         Description: 'Block output data'
            DataType: 'double'
                Size: '[1, 1]'
               Range: [1x1 struct]
        InitialValue: [1x0 double]
               Value: 2
    

   You can change the value of gear from 2 to 1 by typing:

   c.gear.Value = 1;

   However, you cannot change the data type or size of gear. Also, you cannot specify a new value that falls outside the range set by the Minimum and Maximum parameters. For details, see Rules for Modifying Data Values.

7. Save the modified SimState.

   Use this command:

   sf_car_ctx01 = sf_car_ctx01.setBlockSimState(blockpath, c);

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Testing the Modified SimState

1. Define the new stop time for the simulation segment to test.

   1. In the Configuration Parameters dialog box, go to the Solver pane.

   2. For Stop time, enter 20.

   3. Click OK.

   You do not need to enter a new start time because the simulation continues from where it left off.

    Programmatic equivalent

   You can programmatically set the stop time:

   set_param('sf_car','StopTime','20');

2. Start simulation.

   The engine reacts as follows:

   

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Dividing a Long Simulation into Segments

Testing a Chart with Fault Detection and Redundant Logic

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