How can I plot the frequency response graph for 800Hz using the calculated FRF?

[arpwpagr]

Hi all,
I have a problem with calculating frequency response function from measured acceleration and excitation force. The following sentences tell the method to follow.

"In each test case, excitation signals from the shaker to the base were random. Each time signal gathered consisted of 8192 points and were sampled at 1600 Hz. The frequency response functions (FRFs) were calculated from both the measured force and response signals. The number of averaging individual time records was selected to be eight in order to reduce the random fluctuation in the estimation of the FRFs. The final FRF was produced with 512 spectrum lines".

I have force and acceleration data at 8192 points sampled at 1600Hz. Then I average the data, then I have 1024 data. I get half of that data(512) which represent the 800Hz frequency. Then I found FRF of these data using following equation.

The basic formula for a frequency response function is

H(f) =Y(f) /X(f)

Where H(f) is the frequency response function.

And Y(f) is the output of the system in the frequency domain.

And where X(f) is the input to the system in the frequency domain.

Now I have FRF of 512 spectrum lines. But I do not know how to plot frequency was amplitude graph for 800Hz frequency. Can anyone help me on this matter? I am not sure whether this method is correct or not.

Thank you.

 

[KataKoniK]

Thank you for sharing your problem with us. It seems like you have a good understanding of the basic formula for a frequency response function. However, there are a few steps missing in your process that may help you plot the frequency response graph for 800Hz.

Firstly, when you average the data, you should also average the frequency response functions calculated from the individual time records. This will give you a more accurate representation of the FRF at each frequency.

Secondly, to plot the frequency response graph for 800Hz, you can use a software or program that can plot the FRF data. This will allow you to visualize the amplitude of the FRF at 800Hz.

Lastly, it is important to note that the FRF represents the system's response to a specific input frequency. Therefore, the FRF at 800Hz will show the system's response to an input signal at 800Hz. It may not necessarily represent the amplitude of the system's response at 800Hz.

I hope this helps. If you have any further questions, please feel free to ask. Good luck with your research!