ME 470 01 B Finding the Fourier series expansion of a periodic function
Joseph Mahoney
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ME 470 01 B Finding the Fourier series expansion of a periodic function
141 просмотр · 6 лет назад
Joseph Mahoney
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141 просмотр · 6 лет назад
Fourier Series Example: Triangle Wave (Periodic Ramp) and Fourier Coefficients
This video walks through a complete Fourier series expansion for a periodic triangle-wave style signal. You will learn how to (1) identify the smallest repeating period, (2) write the function over one period, (3) compute a0, an, and bn, and (4) assemble the final Fourier series and interpret what the coefficients mean for frequency content.
Key takeaways
Find the period and the fundamental frequency omega = 2*pi/T
Define x(t) over a single period, then extend it by periodic repetition
Compute a0 (DC term), then compute an and bn using the standard integrals
Use integration by parts (or an integral table shortcut) for t*cos( ) and t*sin( )
Simplify trig terms using integer-multiple identities
Recognize when the series becomes sine-only (an = 0) and what that implies
Final result shown in the lesson (for the triangle-wave style example)
x(t) = 5/2 - (5/pi) * sum from n = 1 to infinity of (1/n) * sin(n*(2*pi/3)*t)
Course page for notes, examples, and the full video set
https://sites.google.com/view/mechani...
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#MechanicalVibrations #FourierSeries #SignalProcessing #FrequencyAnalysis #PowerSpectralDensity #VibrationAnalysis
Timestamps
0:00 Problem setup and what the Fourier series represents
0:32 Step 1: identify the period and fundamental frequency
1:32 Step 2: define x(t) over one period (triangle-wave style ramp)
3:20 Step 3: compute a0 (DC term)
6:55 Step 4: set up an integral and why it is tougher than a0
9:20 Using an integral table or integration by parts for t*cos( )
13:05 Simplifying trig terms and showing an = 0
17:05 Set up bn and evaluate the definite integral
20:40 Simplify bn and interpret the 1/n amplitude trend
22:10 Assemble the full Fourier series
23:25 Convergence and what more terms do to the approximation