GUI for Setting Simulink Model Parameters

About the Example

This example shows how to create a GUIDE GUI that sets the parameters of a Simulink® model, runs the simulation, and plots the results in a figure window. The following figure shows the GUI after running three simulations with different values for controller gains.

To get and view the example code:

  1. Copy the example FIG-file and code file to your current (writeable) folder and open the FIG-file in GUIDE with the following commands:

    copyfile(fullfile(docroot, 'techdoc','creating_guis','examples',...
    'f14ex*.*')), fileattrib('f14ex*.*', '+w')
    guide f14ex.fig
  2. From GUIDE Layout Editor, click the Editor button .

    The f14ex.m code displays in the MATLAB® Editor.

How to Use the Simulink Parameters GUI

    Note:   You must have Simulink installed for this GUI to run. The first time you run the GUI, Simulink opens (if it is not already running) and loads the f14 example model. This can take several seconds.

The GUI has a Help button. Clicking it opens an HTML file, f14ex_help.html, in the Help Browser. This file, which resides in the examples folder along with the GUI files, contains the following five sections of help text:

F14 Controller Gain Editor

You can use the F14 Controller Gain Editor to analyze how changing the gains used in the Proportional-Integral Controller affect the aircraft's angle of attack and the amount of G force the pilot feels.

Note that the Simulink diagram f14.mdl must be open to run this GUI. If you close the F14 Simulink model, the GUI reopens it whenever it requires the model to execute.

Change the Controller Gains

You can change gains in two blocks:

  1. The Proportional gain (Kf) in the Gain block

  2. The Integral gain (Ki) in the Transfer Function block

You can change either of the gains in one of the two ways:

  1. Move the slider associated with that gain.

  2. Type a new value into the Current value edit field associated with that gain.

The block's values are updated as soon as you enter the new value in the GUI.

Run the Simulation

Once you have set the gain values, you can run the simulation by clicking the Simulate and store results button. The simulation time and output vectors are stored in the Results list.

Plot the Results

You can generate a plot of one or more simulation results by selecting the row of results (Run1, Run2, etc.) in the Results list that you want to plot and clicking the Plot button. If you select multiple rows, the graph contains a plot of each result.

The graph is displayed in a figure, which is cleared each time you click the Plot button. The figure's handle is hidden so that only the GUI can display graphs in this window.

Remove Results

To remove a result from the Results list, select the row or rows you want to remove and click the Remove button.

Run the GUI

The GUI is nonblocking and nonmodal because it is designed to be used as an analysis tool.

GUI Options Settings

This GUI uses the following GUI option settings:

  • Resize behavior: Non-resizable

  • Command-line accessibility: Off

  • GUI Options selected:

    • Generate callback function prototypes

    • GUI allows only one instance to run

Open the Simulink Block Diagrams

This example is designed to work with the f14 Simulink model. Because the GUI sets parameters and runs the simulation, the f14 model must be open when the GUI is displayed. When the GUI runs, the model_open local function executes. The model_open function performs these tasks:

  • Determines if the model is open (find_system).

  • Opens the block diagram for the model and the subsystem where the parameters are being set, if not open already (open_system).

  • Changes the size of the controller Gain block so it can display the gain value (set_param).

  • Brings the GUI forward so it is displayed on top of the Simulink diagrams (figure).

  • Sets the block parameters to match the current settings in the GUI.

Here is the code for model_open:

function model_open(handles)
if  isempty(find_system('Name','f14')),
	open_system('f14'); open_system('f14/Controller')
	set_param('f14/Controller/Gain','Position',[275 14 340 56])
	set_param('f14/Controller Gain','Gain',...
      'f14/Controller/Proportional plus integral compensator',...

Program the Slider and Edit Text Components

Each slider is coupled to an edit text component to accomplish these tasks:

  • Display the current value of the slider in the edit text box.

  • Update the slider when you enter a value into the edit text box.

  • Update the appropriate model parameters when you interact with the slider and edit text box.

Slider Callback

The GUI uses two sliders to specify block gains because these components enable the selection of continuous values within a specified range. When you change the slider value, the callback performs these tasks:

  • Calls model_open to ensure that the Simulink model is open so that simulation parameters can be set.

  • Gets the new slider value.

  • Sets the value of the Current value edit text component to match the slider.

  • Sets the appropriate block parameter to the new value (set_param).

Here is the callback for the Proportional (Kf) slider:

function KfValueSlider_Callback(hObject, eventdata, handles)
% Ensure model is open.
% Get the new value for the Kf Gain from the slider.
NewVal = get(hObject, 'Value');
% Set the value of the KfCurrentValue to the new value 
% set by slider.
% Set the Gain parameter of the Kf Gain Block to the new value.

While a slider returns a number and the edit text requires a string, uicontrols automatically convert the values to the correct type.

The callback for the Integral (Ki) slider follows an approach similar to the Proportional (Kf) slider's callback.

Current Value Edit Text Callback

The edit text box enables you to enter a value for the respective parameter. When you click another component in the GUI after entering data into the text box, the edit text callback performs these tasks:

  • Calls model_open to ensure that the Simulink model is open so that it can set simulation parameters.

  • Converts the string returned by the edit box String property to a double (str2double).

  • Checks whether the entered value is within the range of the slider:

    If the value is out of range, the edit text String property is set to the value of the slider (rejecting the number you entered).

    If the value is in range, the slider Value property is updated to the new value.

  • Sets the appropriate block parameter to the new value (set_param).

Here is the callback for the Kf Current value text box:

function KfCurrentValue_Callback(hObject, eventdata, handles)
% Ensure model is open.
% Get the new value for the Kf Gain.
NewStrVal = get(hObject, 'String');
NewVal = str2double(NewStrVal);
% Check that the entered value falls within the allowable range.
if  isempty(NewVal) || (NewVal< -5) || (NewVal>0),
   % Revert to last value, as indicated by KfValueSlider.
   OldVal = get(handles.KfValueSlider,'Value');
   set(hObject, 'String',OldVal)
else % Use new Kf value
   % Set the value of the KfValueSlider to the new value.
   % Set the Gain parameter of the Kf Gain Block 
   % to the new value.

The callback for the Ki Current value follows a similar approach.

Run the Simulation from the GUI

The GUI Simulate and store results button callback runs the model simulation and stores the results in the handles structure. Storing data in the handles structure simplifies the process of passing data to other local function since this structure can be passed as an argument.

When you click the Simulate and store results button, the callback performs these tasks:

  • Calls sim, which runs the simulation and returns the data that is used for plotting.

  • Creates a structure to save the results of the simulation, the current values of the simulation parameters set by the GUI, and the run name and number.

  • Stores the structure in the handles structure.

  • Updates the list box String to list the most recent run.

Here is the Simulate and store results button callback:

function SimulateButton_Callback(hObject, eventdata, handles)
[timeVector,stateVector,outputVector] = sim('f14');
% Retrieve old results data structure
if isfield(handles,'ResultsData') & 
	ResultsData = handles.ResultsData;
	% Determine the maximum run number currently used.
	maxNum = ResultsData(length(ResultsData)).RunNumber;
	ResultNum = maxNum+1;
else % Set up the results data structure
	ResultsData = struct('RunName',[],'RunNumber',[],...
	ResultNum = 1;
if isequal(ResultNum,1),
	% Enable the Plot and Remove buttons
% Get Ki and Kf values to store with the data and put in the 
results list.
Ki = get(handles.KiValueSlider,'Value');
Kf = get(handles.KfValueSlider,'Value');
ResultsData(ResultNum).RunName = ['Run',num2str(ResultNum)];
ResultsData(ResultNum).RunNumber = ResultNum;
ResultsData(ResultNum).KiValue = Ki;
ResultsData(ResultNum).KfValue = Kf;
ResultsData(ResultNum).timeVector = timeVector;
ResultsData(ResultNum).outputVector = outputVector;
% Build the new results list string for the listbox
ResultsStr = get(handles.ResultsList,'String');
if isequal(ResultNum,1)
	ResultsStr = {['Run1',num2str(Kf),' ',num2str(Ki)]};
	ResultsStr = [ResultsStr;...
	{['Run',num2str(ResultNum),' ',num2str(Kf),' ', ...
% Store the new ResultsData
handles.ResultsData = ResultsData;
guidata(hObject, handles)

Remove Results from List Box

The GUI Remove button callback deletes any selected item from the Results list list box. It also deletes the corresponding run data from the handles structure. When you click the Remove button, the callback performs these tasks:

  • Determines which list box items are selected when you click the Remove button and remove those items from the list box String property by setting each item to the empty matrix [].

  • Removes the deleted data from the handles structure.

  • Displays the string <empty> and disables the Remove and Plot buttons (using the Enable property), if all the items in the list box are removed.

  • Save the changes to the handles structure (guidata).

Here is the Remove button callback:

function RemoveButton_Callback(hObject, eventdata, handles)
currentVal = get(handles.ResultsList,'Value');
resultsStr = get(handles.ResultsList,'String');
numResults = size(resultsStr,1);
% Remove the data and list entry for the selected value
resultsStr(currentVal) =[];
% If there are no other entries, disable the Remove and Plot 
% and change the list string to <empty>
if isequal(numResults,length(currentVal)),
	resultsStr = {'<empty>'};
	currentVal = 1;
% Ensure that list box Value is valid, then reset Value and String
currentVal = min(currentVal,size(resultsStr,1));
% Store the new ResultsData
guidata(hObject, handles)

Plot Results Data

The GUI Plot button callback creates a plot of the run data and adds a legend. The data to plot is passed to the callback in the handles structure, which also contains the gain settings used when the simulation ran. When you click the Plot button, the callback performs these tasks:

  • Collects the data for each run selected in the Results list, including two variables (time vector and output vector) and a color for each result run to plot.

  • Generates a string for the legend from the stored data.

  • Creates the figure and axes for plotting and saves the handles for use by the Close button callback.

  • Plots the data, adds a legend, and makes the figure visible.

Plot Into the Hidden Figure

The figure that contains the plot is created as invisible and then made visible after adding the plot and legend. To prevent this figure from becoming the target for plotting commands issued at the command line or by other GUIs, its HandleVisibility and IntegerHandle properties are set to 'off'. This means the figure is also hidden from the plot and legend commands.

Follow these steps to plot into a hidden figure:

  1. Save the figure object when you create it.

  2. Create an axes, set its Parent property to the figure object, and save the axes object.

  3. Create the plot (which is one or more line objects), save these line objects, and set their Parent properties to the handle of the axes.

  4. Make the figure visible.

Plot Button Callback Listing

Here is the Plot button callback.

function PlotButton_Callback(hObject, eventdata, handles)
currentVal = get(handles.ResultsList,'Value');
% Get data to plot and generate command string with color 
% specified
legendStr = cell(length(currentVal),1);
plotColor = {'b','g','r','c','m','y','k'};
for ctVal = 1:length(currentVal);
	PlotData{(ctVal*3)-2} = 
	PlotData{(ctVal*3)-1} = 
	numColor = ctVal - 7*( floor((ctVal-1)/7) );
	PlotData{ctVal*3} = plotColor{numColor};
	legendStr{ctVal} = ...
      [handles.ResultsData(currentVal(ctVal)).RunName,'; Kf=',...
      ';  Ki=', ...
% If necessary, create the plot figure and store in handles
% structure
if ~isfield(handles,'PlotFigure') ||...
	handles.PlotFigure = ...
        figure('Name','F14 Simulation Output',...
	handles.PlotAxes = axes('Parent',handles.PlotFigure);
	guidata(hObject, handles)
% Plot data
pHandles = plot(PlotData{:},'Parent',handles.PlotAxes);
% Add a legend, and bring figure to the front
% Make the figure visible and bring it forward

The GUI Help Button

The GUI Help button callback displays an HTML file in the MATLAB Help browser. It uses two commands:

  • The which command returns the full path to the file when it is on the MATLAB path

  • The web command displays the file in the Help browser.

This is the Help button callback.

function HelpButton_Callback(hObject, eventdata, handles)
HelpPath = which('f14ex_help.html');

You can also display the help document in a Web browser or load an external URL. For a description of these options, see the documentation for the web function.

Close the GUI

The GUI Close button callback closes the plot figure, if one exists and then closes the GUI. The handle of the plot figure and the GUI figure are available from the handles structure. The callback executes two steps:

  • Checks to see if there is a PlotFigure field in the handles structure and if it contains a valid figure handle (you could have closed the figure manually).

  • Closes the GUI figure.

This is the Close button callback:

function CloseButton_Callback(hObject, eventdata, handles)
% Close the GUI and any plot window that is open
if isfield(handles,'PlotFigure') && ...

The List Box Callback and Create Function

This GUI does not use the list box callback, but the push buttons reference the list box in their callbacks (Simulate and store results, Remove, and Plot). GUIDE automatically inserts an empty callback function when you add the list box to the layout. It also sets the Callback property to execute this local function whenever users interact with the list box.

You can delete the listbox callback function from the GUI code and also delete the list box's Callback property value in the Property Inspector.

Set the Background to White

The list box create function enables you to determine the background color of the list box. The following code shows the create function for the list box that is tagged ResultsList:

function ResultsList_CreateFcn(hObject, eventdata, handles)
% Hint: listbox controls usually have a white background, change
%       'usewhitebg' to 0 to use default. See ISPC and COMPUTER.
usewhitebg = 1;
if usewhitebg
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