Use MATLAB and Flowcode together with dsPIC development board to carry out the following tasks: Use the recording of the vibration signal provided, (played back via the speaker output of the PC...

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Lab 4
Digital filter design and applications
EQUIPMENT USED: - MATLAB
OBJECTIVES: -
PROCEDURE:-
1. Reading sound file ‘Bearing.wav’ in matlab
[xn fs]=wavread('Bearing.wav');
2. Now, Analyze the frequency spectrum of the audio signal
[xn fs]=wavread('Bearing.wav'); % Reading audio signal
L=length (xn); % length of signal
Y = fft(xn,L); % DFT of audio signal
% Creating one sided spectrum of signal
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = fs*(0:(L/2))/L;
plot(f,P1)
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('Frequency (in hertz)');
title('Magnitude Response');
Fig 1: Frequency Response of Sound Signal


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Now, from above spectrum we found the frequency but we are not able to recognize the
frequency. So we plot another graph from 1Hz to 500Hz so that we are able to recognize
the frequency component
[xn fs]=wavread('Bearing.wav'); % Reading audio signal
L=length (xn); % length of signal
Y = fft(xn,L); % DFT of audio signal
% Creating one sided spectrum of signal
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = fs*(0:(L/2))/L;
x= f(1:37037);
y = P1(1:37037);
plot(x,y)
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('Frequency (in hertz)');
Fig 2: Frequency Response From 1Hz to 500Hz of Audio Signal
From above Spectrum we analyze that
1. Fundamental Frequency of bearing race = 435 Hz and relative amplitude A =0.3
2. Fundamental Frequency of components transmitted through the machine structure
from the cutter rotating at 5100rpm = 85 Hz and relative amplitude A =0.05
3. Fundamental Frequency of 3-phase power supply of a servo motor drive on the
earing housing axis. = 300Hz and relative amplitude A =0.1


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3. Establishing lowest possible sampling Rate
For this we need to find the frequency which can cater the bearing race fundamental
frequency and its harmonics. For which we first plot the frequency response upto
1000Hz
[xn fs]=wavread('Bearing.wav'); % Reading audio signal
L=length (xn); % length of signal
Y = fft(xn,L); % DFT of audio signal
% Creating one sided spectrum of signal
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = fs*(0:(L/2))/L;
x= f(1:74074);
y = P1(1:74074);
plot(x,y)
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('Frequency (in hertz)');
Fig 3: Frequency Response from 1Hz to 1000Hz of Audio Signal
From above spectrum we found that
1. Harmonics from components transmitted through the machine structure from the
cutter rotating at 5100rpm dies down at 255Hz and we get three harmonics from this.


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2. Third Harmonics from 3-phase power supply of a servo motor drive on the bearing
housing axis exists with relative amplitude of about 0.08...