how to get transfer function (bode plot) of this time response?

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Zhe Liu 2016-5-29

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评论： Star Strider 2016-5-30

step response.png

I have a time response of a pressure step (not unit), but I find it difficult for me to get a transfer function(bode plot). I was thinking FFT or bode but I think I was not in the right track....Any help?

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Star Strider 2016-5-29

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First do a fft of your signal if you are interested in its frequency characteristics.

To approximate a linear system to it, use tfest first, then bode to see how accurately you have approximated the frequency characteristics of your signal.

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Zhe Liu 2016-5-30

Also the time response plot has values lower than 1.5 (because pressure step is not unit in my case, from 1.5 to 1.506) which makes me think this might be undershoot...

Star Strider 2016-5-30

As with all ‘real-world’ problems, you have to experiment to get the result you want.

That the initial value of the response is negative likely indicates a response lag (phase lag), typical of inductive (electrical) or mass-displacement (mechanical) systems. That will be accounted for in your model.

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