How to set simulink model parameter from GUI during simulation?

I want to set the gain(value of K) in the simulink block when this model is simulating.

I created a GUI contains a button and an edit text(tagged "text_box"), and the callback function of this button will set the gain by specifying the K in base work space.

    % --- Executes on button press in FK_button.
    function FK_button_Callback(hObject, eventdata, handles)
    % hObject    handle to FK_button (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    global K;

    text=get(handles.text_box, 'String');
    value = str2double(text);

    K = value;

However, the simulink block only read the value of K in work space when I started simulation. During the simulation, if I press the button, the K value in base work space would change to the value I set, but the value of K in simulink wouldn't change.

I've also tried using set_param API to change the K in simulink by

    % --- Executes on button press in FK_button.
    function FK_button_Callback(hObject, eventdata, handles)
    % hObject    handle to FK_button (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    global K;

    text=get(handles.text_box, 'String');
    value = str2double(text);

    %gui_variable is the model file name
    set_param('gui_variable/Gain','Gain', value);

But I'll got error saying:

    Error using robotics_gui_2>FK_button_Callback (line 429)
    Invalid setting in Gain block 'Gain' for parameter 'Gain'

What can I do to alter K in simulink during simulation?

[rangan]

I had the same problem but solved it using this

value = get(hObject,'String')

string = value{1} // Converting cell to string

set_param([bdroot '/Gain'],'Gain',string)

Answer 1

[Ilham Hardy]

   set_param('gui_variable/Gain','Gain', value);

Is value string?

[Po-Jen]

No, it's double. Should I use string?

[Ilham Hardy]

Yes

Answer 2

[Chandrasekhar]

In the callback function 'function FK_button_Callback(hObject, eventdata, handles)' write the following code assignin('base', 'K', val); // val will be the value that you want to give for the gain.

the gain block in the Simulink model will read the K value from the workspace.

[Po-Jen]

If I started the simulation before I pushed the button. "assignin('base', 'K', val);" only changes the value of workspace, but the value in simulink model doesn't change.

[Chandrasekhar]

the K value in the gain block will access the value from the workspace. I think it should work

[Po-Jen]

I've tried before I left the comment, but it doesn't work. It's effect is the same as using K = value; in my callback function.

[Kaustubha Govind]

Po-Jen: Is the model running when the value of K changes in the base workspace? If yes, you need to update the model using set_param('modelname', 'SimulationCommand', 'update') to force Simulink to notice the new value.