FRF Plotting
7 views (last 30 days)
Show older comments
I want to plot FRF vs Frequency graph.I have a matrix 'a' of acceleration & a force matrix 'f' both of 30000X1 size, collected in 3secs with a time step of 0.0001 sec.I am using the following steps to plot FRF. ffa=fft(a); fff = fft(f); frf, H=ffa./fff; aH =abs(H); x=0:0.1:30000; semilogy(aH) After plotting,I am not getting the correct first natural frequency at the first peak compared to the one I obtained from ANSYS (=14.5Hz).For plotting on Y-axis wether we have to take FRF in dB by using 20*log10(aH)?Where am I wrong in the procedure? Does the time steps have any role while finding fft?.
Answers (1)
bym
on 26 Jun 2011
Your x-axis scaling is incorrect. When you do
semilogy(aH)
it plots the amplitude versus the matrix index. You need to scale the x axis. See
doc fft
for example and detailed explaination
0 Comments
See Also
Categories
Find more on Spectral Measurements in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!