Why an IF statement is being infringed while output results clearly says it should be executed?

Question

Context: I'm using Matlab/Simulink to simulate a circuit where I need to follow a reference. To simplify it: below reference current then apply more current, above reference current then apply less current. To achieve this, I have to control two devices (Sa and Sb) which basically closes applying a 1 in my code and opens with a 0 (both at the same time).

Now, I'm having these results where the important graphs are S1 Current, S-Function/2 and S-Function/1 and the final question: why, considering the following code, would the S-Function/2, this is THY[], stay at 1 while clearly there are lapses of time where S-Function/1, this is IGBT[], is 0?

The next code is inside an S-Function that I use inside Simulink. This is the entire code

for (i=0; i<width; i++){
if (*Is[i] <  *Iref[i]){
    //IGBT[] is S-Function/1 and THY[] is S-Function/2
    //Is[] is S1 Current and Iref[] is Reference Current 1
    IGBT[i] = 1.0;

    if ( IGBT[i] == 0.0){
    THY[i] = 0.0;   
    }
    else {
    THY[i] = 1.0; 
    }
    }
    else {
    IGBT[i] = 0.0;   
    }
}

score 0 · Answer 1 · answered Apr 10 '18 at 01:55

Look at your code:

IGBT[i] = 1.0;

if ( IGBT[i] == 0.0) {
    THY[i] = 0.0;         // <--- will never be executed
}
else {
    THY[i] = 1.0; 
}

Assuming it's executed sequentially (i.e. no threads), You always sets IGBT[i] to be 1 and then the else part will be executed resulting in THY[i] equals 1, and therefore always stays 1.

Monk · Accepted Answer · 2018-04-10T02:05:51.903

I am not sure but I think there is a problem in code:

for (i=0; i<width; i++){
if (*Is[i] <  *Iref[i]){
    //IGBT[] is S-Function/1 and THY[] is S-Function/2
    //Is[] is S1 Current and Iref[] is Reference Current 1
    IGBT[i] = 1.0;

    if ( IGBT[i] == 0.0){ // condition 1
    // if condition 1 is true then execute this
    THY[i] = 0.0;   
    }
    else {
    // if condition 1 is false then execute this
    THY[i] = 1.0; 
    }
    }
    else {
   // this condition will never be executed
    IGBT[i] = 0.0;   
    }
}

Now if condition 1 is true then THY[I] = 0.0; will be executed, if condition is false then, THY[i] = 1.0;. In your code

 else {
    IGBT[i] = 0.0;   
    }

is a kind of dead code and it will never be excuted. You need to replace the else followed by if condition with else if(condition) so that second else can be executed.

Also 1 more thing

IGBT[i] = 1.0; // IGBT[i] is updated

        if ( IGBT[i] == 0.0){ // IGBT[i]  is compared ... wow

I would recommend you to read about comparison between float and double.

Why an IF statement is being infringed while output results clearly says it should be executed?

2 Answers2