How i can determine sinusoid frequency ?
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Muna Shehan
am 1 Apr. 2017
Kommentiert: Star Strider
am 6 Apr. 2017
Hi; Pleas can anyone explain how i can determine sinusoid frequency if I have a step response where the data form is two vectors one for the acceleration and the other is time, when i transfer the plot from time domain to frequency domain i use fft; however i am confused how i can specify f0 when i read
I will appreciated for any explanation. Thanks in advance
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/162474/image.jpeg)
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Star Strider
am 1 Apr. 2017
Bearbeitet: Star Strider
am 2 Apr. 2017
It could be difficult to get a dominant peak with the signal you posted, since it could be a heterodyne of several frequencies. You will have to take the fft (link) of your signal and use your judgement.
It will be easier if you subtract the mean of the time-domain signal before you take the fft (link). This will eliminate the ‘0 Hz’ peak.
EDIT — 01:48 UCT 2017 04 02
The true resonant frequencies of your system are determined by the eigenvalues of your ‘A’ matrix. For your simulation, they appear to be the eigenvalues of:
Aqcar = [0 1 0 0;-kus/mus -c/mus k/mus c/mus;0 -1 0 1;0 c/ms -k/ms -c/ms];
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Image Analyst
am 1 Apr. 2017
Subtract the mean and take the fft using fft() or pwelch(). Then scan it and look for the max magnitude. You didn't supply data so I can't do much other than speculate some code:
spectrum = fft(yourSignal - mean(yourSignal));
[maxValue, indexOfMaxValue] = max(abs(spectrum));
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