Why does my matlab code cannot detect the number of periods in a specific time range

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Ramo 2024-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/2126876-why-does-my-matlab-code-cannot-detect-the-number-of-periods-in-a-specific-time-range

回答： Image Analyst 2024-6-10

I have developed a matlab code which imports pNRF Files that contain a measurement signal of light distance of a wheel surface in order to detect the number of cracks on that surface. There are in the file 3 signals, 2 rotary encoder signals and one light distance signal.

The Code does mostly what I want it to do:

It can import the Data accurately and successfully.
It can plot all the 3 signals
It can detect the cracks automatically using a threshold

One thing thats important and that the code is doing wrong, is that it detects the wrong number of the periods in the time range where a crack is being detected. (See the following picture, the back rectangles are the Cracks detected).

Now what I would like to do is to calculate the number of the Periods on the Signal Ch B1 (increment Encoder A) in the time where a crack is being detected. In this example the number of the periods is about 5,2 Periods of the first Crack and about nearly 1 Period of the second crack.

This is a substract of the 200line Code that i have to determine how many cracks I have:

% Zusammenfassung der Risse anzeigen
disp('Anzahl der detektierten Risse:');
disp(numCracks);
disp('Breite der detektierten Risse in Inkrementen und Mikrometern:');
for i = 1:numCracks
    rissIndizes = risseGruppen.PixelIdxList{i};
    Crackstart = min(rissIndizes);
    Crackend = max(rissIndizes);
    Periods_Yellow_Signal = locs_gelb(locs_gelb >= Crackstart & locs_gelb <= Crackend);
    CracksthicknessinPeriods = length(Periods_Yellow_Signal);
    rissBreiteMicrometer = CracksthicknessinPeriods * INC_TO_MICROMETER;
    fprintf('Crack %d: Thickness = %d Periods, %.2f Micrometer (Signal: Ch B1_A)\n', i, rissBreiteInkrement, rissBreiteMicrometer);
    fprintf('Number of Periods: %d\n', rissBreiteInkrement);
end

What am I doing wrong here?

I would so thankful for any help! Thanks a lot in advance.

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Voss 2024-6-9

Please share the complete actual code and any necessary data.

Ramo 2024-6-9

Hi @Voss, I just sent you the complete Code as a message, but feel free to answer here. The only necessary data that I upload into the Code is the .pNRF File which contains the measured signals, but I unfortunately cannot upload it here due to its data typ..

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Answer 1

Image Analyst 2024-6-10

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在 MATLAB Online 中打开

Is locs_gelb the yellow signal? It looks like you've already determined how many cracks you have and your loop simply inspects each crack one at a time and gets the number of elements in the crack. The CracksthicknessinPeriods should be indexed by (i) otherwise you're just overwriting each crack length.

CracksthicknessinPeriods(i) = numel(Periods_Yellow_Signal);

Then after the loop you can do

totalCrackLength = sum(CracksthicknessinPeriods)

However you can also get that without doing the loop at all (if you're not interested in individual crack lengths) just by summing your threshold criteria

totalCrackLength = sum(locs_gelb > yourThreshold)

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

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