Index exceeds number of array elements (4).

Hello, I am trying to perform active battery equalisation by using flyback topology. However, when ever I use more than 4 batteries, I get the error "Index exceeds number of array elements (4)".

How do I resolve this issue?

In the code, pwm(n) is a pulse given to the battery through a switch. soc(n) is the state of charge of a battery. s represents a stop signal when all state of charge is equal.

function [pwm1, pwm2, pwm3, pwm4, pwm5, s] = fcn(soc1, soc2, soc3, soc4, soc5)

    pwm1 = 0;
    pwm2 = 0;
    pwm3 = 0;
    pwm4 = 0;
    pwm5 = 0;
    
    if (soc1 > soc2 || soc1 > soc3 || soc1 > soc4 || soc1 > soc5)
        pwm1 = dutycycle(50, 1/47000);
    end
    
    if (soc2 > soc1 || soc2 > soc3 || soc2 > soc4 || soc2 > soc5)
        pwm2 = dutycycle(50, 1/47000);
    end
    
    if (soc3 > soc1 || soc3 > soc2 || soc3 > soc4 || soc3 > soc5)
        pwm3 = dutycycle(50, 1/47000);
    end
    
    if (soc4 > soc1 || soc4 > soc2 || soc4 > soc3 || soc4 > soc5)
        pwm4 = dutycycle(50, 1/47000);
    end
    
    if (soc5 > soc1 || soc5 > soc2 || soc5 > soc3 || soc5 > soc4)
        pwm5 = dutycycle(50, 1/47000);
    end
    
    if (soc1 == soc2 && soc1 == soc3 && soc1 == soc4 && soc1 == soc5)
        s = 1;
    else
        s = 0;
    end
end

[Scott MacKenzie]

There are no vectors in your function. The error must be originating outside the function in the rest of your code somewhere. More details would help.

[indrani chatterjee]

I've posted all the code that I've written.

Here is the model:

[Scott MacKenzie]

Hmm, well I don't know then. I don't use this toolbox. Does the error message give a line number or a line of code?

What about the dutycycle function? Isn't the first argunt supposed to be a vector? You're passing in a scalar.

[indrani chatterjee]

The error has been resolved. The transformer winding resistance was set for only 3 secondaries, so it was showing index error.

I have now set the winding resistance for 5 secondaries, corresponding to 5 batteries. I'm not getting the error now.

Thank you for your time professor MacKenzie.

Answer 1

[Cris LaPierre]

The error is not coming from this function. You don't index anything. Somewhere else in your code you are trying to extract an element of your array that doesn't exist.

a = 1:4;
% works
a(4)

ans = 4

% doesn't work
a(5)

Index exceeds the number of array elements (4).

[indrani chatterjee]

I've posted all the code that I've written.

I do understand what the error is trying to say. However, I can't understand why I'm getting the error with this code when I haven't used any loops.

[Cris LaPierre]

Perhaps you have overwritten the dutycycle function accidentally? Type the following command and share the results:

which dutycycle

On my computer, the result is "C:\Program Files\MATLAB\R2021a\toolbox\signal\signal\dutycycle.m".

Your function returns a result and no error if I pass in made-up values.

soc1 = 1;
soc2 = 2;
soc3 = 3;
soc4 = 4;
soc5 = 5;

[pwm1, pwm2, pwm3, pwm4, pwm5, s] = fcn(soc1, soc2, soc3, soc4, soc5)

pwm1 = 0

pwm2 = 0.0011

pwm3 = 0.0011

pwm4 = 0.0011

pwm5 = 0.0011

s = 0

% your function
function [pwm1, pwm2, pwm3, pwm4, pwm5, s] = fcn(soc1, soc2, soc3, soc4, soc5)

    pwm1 = 0;
    pwm2 = 0;
    pwm3 = 0;
    pwm4 = 0;
    pwm5 = 0;
    
    if (soc1 > soc2 || soc1 > soc3 || soc1 > soc4 || soc1 > soc5)
        pwm1 = dutycycle(50, 1/47000);
    end
    
    if (soc2 > soc1 || soc2 > soc3 || soc2 > soc4 || soc2 > soc5)
        pwm2 = dutycycle(50, 1/47000);
    end
    
    if (soc3 > soc1 || soc3 > soc2 || soc3 > soc4 || soc3 > soc5)
        pwm3 = dutycycle(50, 1/47000);
    end
    
    if (soc4 > soc1 || soc4 > soc2 || soc4 > soc3 || soc4 > soc5)
        pwm4 = dutycycle(50, 1/47000);
    end
    
    if (soc5 > soc1 || soc5 > soc2 || soc5 > soc3 || soc5 > soc4)
        pwm5 = dutycycle(50, 1/47000);
    end
    
    if (soc1 == soc2 && soc1 == soc3 && soc1 == soc4 && soc1 == soc5)
        s = 1;
    else
        s = 0;
    end
end

[indrani chatterjee]

[Cris LaPierre]

I just noticed that this is in relation to a simulink model. Can you please share a screenshot with the error message showing?

[indrani chatterjee]

[Cris LaPierre]

The error does not appear to be with your MATLAB Function block (my best guess). If it were, I believe the info under the error message would be "Component: MATLAB Function | Category: Coder error". Try commenting out the MATLAB Function block and see if you still get the error.

Also, is that the full error message? I feel like there should be more that what is shown. If there is, please copy/paste all of the text.

[indrani chatterjee]

Yes, this is the full error message.

[Cris LaPierre]

And what happens when you comment out the function block?

[indrani chatterjee]

The error has been resolved. The transformer winding resistance was set for only 3 secondaries, so it was show index error.

I have now set the winding resistance for 5 secondaries, corresponding to 5 batteries. I'm not getting the error now.

Thank you for your time Cris.