MATLAB Answers

Plotting Fourier Series Function

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random1072
random1072 on 28 Sep 2020
Answered: Nikhil Sonavane on 1 Oct 2020
Hello I am trying to plot a Fourier Series for t = 0 to 5T. I have attached my code as well as my current plot output (which is obviously wrong). Not really sure where to go from here any help would be great.
Pressure = 95 + 9 - 1.1 sin cos 13.7t + 5 13.7t - 3 .3 sin .5 cos 27.3t + 7 sin 41t + 1 sin 55t + 0.6 27.3t - 2.6 cos 41t - 1.6 cos 55t - 1.7 = 95 + 9.1 + 2.2 sin sin (13.7t-7° (55t-6l°) ) + 6 .4 + 1.8 sin (27.3t-34°) + 7.5 sin (41t-21°) sin (68.5t-71°)
A_0 = 95;
A_1 = 9.1;
w_1 = 13.7;
theta_1 = -7;
A_2 = 6.4;
w_2 = 27.3;
theta_2 = -34;
A_3 = 7.5;
w_3 = 41;
theta_3 = -21;
A_4 = 2.2;
w_4 = 55;
theta_4 = -61;
A_5 = 1.8;
w_5 = 68.5;
theta_5 = -71;
t = [0;5*.459;5*.230;5*.153;5*.114;5*.092];
y = A_0 + A_1*sin(w_1*t+theta_1) + A_2*sin(2*w_2*t+theta_2)...
+ A_3*sin(3*w_3*t+theta_3) + A_4*sin(4*w_4*t+theta_4)...
+ A_5*sin(5*w_5*t + theta_5);
plot (t,y)
*Current output below
*What Output is supposed to look like

Answers (1)

Nikhil Sonavane
Nikhil Sonavane on 1 Oct 2020
The error which I could notice is you are plotting y only at 5 points that is at 5 values of t.If you increase the number of points between 0 and 5T, you may get the desired output. I tried out the following and it worked for me-
t = [0;5*.459;5*.230;5*.153;5*.114;5*.092]; %Remove this from the code and replace it with the next line
t=linspace(0,5*0.092,1000); % Now t has 1000 linearly spaced values between 0 and 5*0.092
Here, 1000 is a value which I just randomly added. You can refer to the Sampling Theorem for more understanding.

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