Matlab Function Block in a Simulink Model

I have a Matlab Function Block within a Simulink model that I am using to control some of the switches I have in the model. The function takes real-time voltage measurments from the model, and outputs switching signals.

When I run the model, it seems that it enters an infinite loop(it says "Running" without showing any progress in the execution). And by "Ctrl + C", I get it to forward one step and it is stuck again unless I keep clicking "Ctrl + C". I am not sure what it is behaving this way.

Here is the part of the code that gets stuck:

function [GR, GS, GT] = fcn(DcVolt, VA, VB, VC, VR, VS, VT, limit)
%INITIALIZE OUTPUTS
GR = 0;
GS = 0;
GT = 0;
% INITIALIZE THE PERSISTENT VARIABLE TO STORE THE PREVIOUS VALUE OF VDC
persistent prev_VDC;
if isempty(prev_VDC)
    prev_VDC = 0;
end
prev_VDC = DcVolt;  
    function [ARM,DISARM] = ARM_SWITCH (VAN,VDC,V_PREV, V_NEXT)
        if (VDC >= VAN) || (V_PREV >= V_NEXT)
            DISARM = 1; ARM = 0;
        else
            DISARM = 0; ARM = 1;
        end
    end
    function [DISABLE] = DISABLE_SWITCH (VDC, VDCPREV)
        if (VDC > (VDCPREV+15))
            DISABLE = 1;
        else
            DISABLE = 0;
        end
    end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
while DcVolt < limit
    [ARM_R, DISARM_R] = ARM_SWITCH (VA, DcVolt, VC, VB);
    [ARM_S, DISARM_S] = ARM_SWITCH (VB, DcVolt, VA, VC);
    [ARM_T, DISARM_T] = ARM_SWITCH (VC, DcVolt, VB, VA);
    
    if (ARM_R==1) 
        GR = 1;
    else
        GR = 0;
    end
    
    if (ARM_S==1)  
        GS = 1;
    else
        GS = 0;
    end
    
    if (ARM_T==1) 
        GT = 1;
    else
        GT = 0;
    end
    [DISABLE_R] = DISABLE_SWITCH (DcVolt, prev_VDC);
    if (DISABLE_R == 1)
        GR = 0;
    end
    [DISABLE_S] = DISABLE_SWITCH (DcVolt, prev_VDC);
    if (DISABLE_S == 1)
        GS = 0;
    end
    [DISABLE_T] = DISABLE_SWITCH (DcVolt, prev_VDC);
    if (DISABLE_T == 1)
        GT = 0;
    end
end
end

Answer 1

[Fangjun Jiang]

You can't expect to achieve your goal by doing this.

The sequence of the MATLAB Function block can be simplified as this, read the inputs, execute the code, generate the outputs.

The value of "DcVolt" and "limit" won't change until next simulation step, so you have an infinite loop.

The value of "DcVolt" might change during this time, but it is not read in.

Change from "while" to "if" might help you achieve your goal if everything else (like simulation step) have the right set up.

But overall, you can't expect the Simulink model or simulaiton to deal with "real-time voltage measurments". You didn't mention any other element like Simulink Desktop Real-Time

[Paul]

I'm actually shocked that the two helper functions can be defined inside the body of the main function. Did not know that nested functions are supported.

[Fangjun Jiang]

Yeah. I launched a campaign/survey to request allowing functions inside a m script. Now, local functions can be defined in a script or function.

[HASSAN ABDELGABIR]

Yes I missed that. Thank you :)