I have 2 unprocessed signals X and Y measuring the vibrations of a rotating shaft at const. speed 633.33 Hz. My goal is to extract only a specific frequency component (say, 1X or .35X) and plot orbits (X signal plotted on the Y-signal) for them. I took a raw signal and I applied a low pass filter using a Butterworth filter. he gave me a smooth signal in the time domain. Now when I try to apply an oil filter passband filter between frequencies (from 630 Hz to 640 Hz), it does not work properly. I do not know if I am doing this correctly. The following picture after applying a low-pass filter (butterworth).
This is another time when I applied low pass and band pass filters. The original signal is a complete change.
, - 1X.
MATLAB .
L = length(X); % length of signal
fs= 2e6; % sampling frequency
df = fs/L; % Frequency window
dt = 1/df; % time window
%calculate time axis
T = (0:dt:(L-1)*dt)';
subplot(3,2,1);
plot(T,X);
title('before filtering X signal')
subplot (3,2,2);
plot(T,Y);
title('before filtering Y signal')
subplot(3,2,5);
plot(X,Y);
title('Orbits before filtering')
X = detrend(X,0); % Removing DC Offset
Y = detrend(Y,0); % Removing DC Offset
% Butterworth low pass filter to remove high frequency components
[b2,a2] = butter(6,5*633/(fs/2),'low');
dataInX = X;
X = filter(b2,a2,dataInX); %filter command filters
dataInY = Y;
Y = filter(b2,a2,dataInY);
% butter worth band pass to only plot for 1X frequency component
[b1,a1] = butter(1,[633/(fs/2) 640/(fs/2)],'bandpass');
dataInX = X;
X = filter(b1,a1,dataInX); %filter command filters
dataInY = Y;
Y = filter(b1,a1,dataInY);
subplot(3, 2 ,3);
plot(T,X);
axis tight
title('X signal after filtering')
subplot(3,2,4);
plot(T,Y);
axis tight
title('Y signal after filtering')
subplot(3,2,6);
plot(X,Y);
title('Orbit after filtering')
axis tight
.
DSP. - .