Help with threshold value accelerometer

Ben Anderson

2021 2 23

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Hi there i am attempting to create a step counter powered by MATLAB mobile and have been using the webpage: https://uk.mathworks.com/help/matlabmobile_android/ug/counting-steps-by-capturing-acceleration-data.html

However once it uses the findpeaks function it mentions changing the threshold value and states "This threshold should be tuned experimentally to match a person's level of movement while walking, hardness of floor surfaces, etc." was wondering if anyone had any ideas what i could do here to experiment with different thresholds as the one it uses:

minPeakHeight = std(magNoG);
[pks,locs] = findpeaks(magNoG,'MINPEAKHEIGHT',minPeakHeight);

This works to an extent but feel it is very prone to undercounting steps.

Hope someone can help thanks.

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Mathieu NOE 2021-2-24

hello Ben

I assume you will have to do a few experiments to set up the threshold value.

FYI, there is another alternative based on triggering on positive or negative slopes of the signal , but this requires too a threshold.

maybe a little amount of bandpass filtering would also help to remove artifacts (like short pulses due to mechanical shocks)

Ben Anderson 2021-2-24

thanks ill look into that, yeah i have done experiments but cant understand what the treshold value should change to instead of the standard deviation.

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