Calculating FRF & Coherence between Acceleration Signals

[serbring]

Hello, I'm a newbie of signal processing, I would like to calculate a frf between two acceleration signals. I have several realizations of each signal. These signals are stationaries and they aren't triggered, so signal arrays doesn't have the same length. I have got these acceleration signal by two accelerometer placed at the top and at the bottom of a suspensed element. These element should have a natural frequency in working condition roughly of 2/3Hz.
How can I have a good frf and the coherence function estimations between the two signals? Can I simpy average frf and coherence function of every realizations? I hope to have well explained my problem, if there are any doubt, I will give all the necessary information

 

[serbring]

Anyone can help me?

 

[berkeman]

Hello, I'm a newbie of signal processing, I would like to calculate a frf between two acceleration signals. I have several realizations of each signal. These signals are stationaries and they aren't triggered, so signal arrays doesn't have the same length. I have got these acceleration signal by two accelerometer placed at the top and at the bottom of a suspensed element. These element should have a natural frequency in working condition roughly of 2/3Hz.
How can I have a good frf and the coherence function estimations between the two signals? Can I simpy average frf and coherence function of every realizations? I hope to have well explained my problem, if there are any doubt, I will give all the necessary information

I'm not sure that the ME forum is the right place for your question. Could you please give more details about the setup? If you can present more details, maybe it will make sense to move this thread to EE or elsewhere.

 

[JolileChat]

Hello, I'm a newbie of signal processing, I would like to calculate a frf between two acceleration signals. I have several realizations of each signal. These signals are stationaries and they aren't triggered, so signal arrays doesn't have the same length. I have got these acceleration signal by two accelerometer placed at the top and at the bottom of a suspensed element. These element should have a natural frequency in working condition roughly of 2/3Hz.
How can I have a good frf and the coherence function estimations between the two signals? Can I simpy average frf and coherence function of every realizations? I hope to have well explained my problem, if there are any doubt, I will give all the necessary information

Ok, let me try to figure out what you are trying to find.

It's a FRF of a structure, where both input and output are measured by accelerometers.

What do you mean by a realization? The system is being excited continuously, and a realization is a period of time where you perform the signal acquisition?

Is the excitation a white noise? Or, at least, can you consider it white noise? Does it matter where you crop the signals, in order to perform the calculations?

If it doesn't matter, go for the average of FRFs between the "realizations". Don't forget to apply the windows functions, as needed, and to use the transfer function evaluation through power spectra.