Performance of tfestimate at high frequencies

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Angelica
Angelica on 8 Sep 2014
Answered: Harryboy on 10 Oct 2019
Hi, It was recommended to me to try to use the function tfestimate instead of the system identification toolbox to try to do sys id using data driven modelling. To first test my understanding of tfestimate, I took a known system (low pass filter, cutoff = 5Hz) and a step input, and used simulink to generate the output. I then fed the input/output into tfestimate to see what it does; below are the results.
For parameters I used window = 2^10 (largest power of 2 which was less than the length of my input vector), and default 50% overlap and nfft = 2^10 as well (lower nfft values had similar trends,just less noise). At low frequencies, it looks almost alright. But for higher frequencies, the tfestimate results are way off. I don't have much background in spectral analysis and therefore am not too confident in parameter selection. I feel like tfestimate must be able to do a better job if configured correctly. Can please give me any suggestions for using this function?
Thank you!
tfestimate Output:

Answers (1)

Harryboy
Harryboy on 10 Oct 2019
Hello Angelica,
I also have a system with a frequency mode at 6500 Hz, and even for me the tfestimate is given NAN for amplitude values. Did you find the right way to configure the command?
Thank you and kind regards,
Hari

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