Register to reply 
Finding the frequency of an arbitrary, timevarying load 
Share this thread: 
#1
Jan2813, 04:25 PM

P: 2

Hi everyone,
So I have timevarying force data. The force acts as a concentrated load. The force does not vary periodically/harmonically, it just has a general variation with time. My main question is: How do I determine the corresponding frequency of this force data? Also, if I'm using MATLAB and I have a data vector of this force's time variation, how do I use MATLAB to determine the corresponding frequency data? Do I use the fft() function? Any help/insight would be appreciated! Let me know if you need any more details and I will happily provide them. Thanks 


#2
Jan2813, 05:01 PM

Mentor
P: 11,900

If it is not periodic, it does not have a single frequency.



#3
Jan2813, 11:12 PM

P: 2

Thanks for the helpful reply, I appreciate it.
What exactly does fft() give me? For instance, say I define my force vector as V=[2 6 2 9 10 3 . . . .] then plug in fft(V) in MATLAB. What is the physical significance of the resulting numbers? Are they the frequency of the data of the vector? Basically my goal is to first plot my force as a function of time from the given data, F(t). I have this data so its very easy. Then I want to plot the force as a function of its frequency, F(f) using a Fourier transform. How do I do this? Any help/advice would be greatly appreciated. Let me know if you need my to provide more info. 


#4
Jan2913, 06:10 AM

Mentor
P: 11,900

Finding the frequency of an arbitrary, timevarying load
The mathematical interpretation of a Fourier transformation (FT): If you see a peak at some value x, your data has an oscillating signal with a frequency of x. If you see multiple peaks (or even some broad distribution), you have multiple different oscillations in your signal at the same time (or chaos). 


Register to reply 
Related Discussions  
Capacitance  finding the voltage across a capacitor given a time varying current  Engineering, Comp Sci, & Technology Homework  4  
Another question on radiation of time varying arbitrary source.  Classical Physics  3  
Constant Power to a Varying Load  Electrical Engineering  9  
Uniformly Varying Load/Uniform Load to Concentrated Point Load  Engineering Systems & Design  4  
Calculate rise time value for a sinusoidal signal at an arbitrary frequency (f_0)  Introductory Physics Homework  7 