So I have to "window" my signal as you can see in the picture, you can also notice that I remove the offset of the signal.
And now I implement again the FFT with this signal, and this is the output.
It still doesn't represent the real value of the amplitude, any idea?
I think that both of you are correct encouraging me to use a window function to reduce the spectral leackage, but I understand that the window function depends on the frecuencies and the amplitudes that you have in your data. Have a look at the next pictures that represent two different periods...
Hello,
I want to implement the fast fourier transformation on an aperiodic signal, which you can see in the next picture:
The first question came here, can I use the FFT in an aperiodic singnal?
Once I execute the matlab code I obtain the output of the transformation, which you cant see in...
[djs
"Ok I think I know what you are trying to do. You have just the process variable, and wish to detect deviations from what is should be. So assuming that the system is controller by a half way decent controller, I suggest that you use the output from a low pass filter as your reference...
Yes, you are right, at the end what I'm trying to do is the same as djs has said. But in my case I can't compare the SP and PV values to detect those function anomalies, instead I need some type of function (like as i said a low pass filter, Kalman filter...) to compare the raw data with.
Maybe you can reduce this lag introduced by the low pass filter to almost zero, and with this you have a filtered signal to compare with the real signal.
I understand what you are saying, but I do not want to detect failures in the control system (in my case it is formed by PID controllers) such as low gain or overshoots, instead I want to monitor raw data measured directly from the process, and detect in this data the anomalies. I imagine that...
I'm trying to implement and algorithm which should have the capability to detect some types of anomalies or failures on a process variable like ripples or overshoots. First of all, I want to adjust my process signal with some type of mathematical function, I was thinking on a low pass filter or...
