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Transfer function from measured input signal and output signal

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Ill ch
Ill ch on 28 Sep 2019
Commented: Ill ch on 17 Dec 2019
Dear Matlab and Simulink user,
Is there any way with parameter estimation toolbox or any another method to generate transfer function from multiple inputs and multiple outputs Signals?


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Ill ch
Ill ch on 28 Sep 2019
Dear Star STrider,
Great your kind help.
Thank you very much for this link. Yes i found their solution for multiple input output.
with iddta one can generate data for tfest. y and u one can give as a matrix form.
Ill ch
Ill ch on 28 Sep 2019
one small query if you can help me:
if i have in output signal (data1 as a time, data 2 with value) and in input signal ( data 1 just value) how i can use this ? should i need to use in bothe same time vector or sampling time is enough instead of time vector? Thank you in advance
sys = tfest(data,np,nz) ; % data from iddata(y,u,Ts)

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Accepted Answer

Star Strider
Star Strider on 28 Sep 2019
The sampling interval ‘Ts’ is enough. Note that all your data must be sampled all with the same sampling interval. If they are not, you need to interpolate them to the same sampling interval with the resample function first.
I usually calculate the sampling interval as:
Ts = mean(diff(time));
For iddata, the output signal ‘data2’ is ‘y’, the input signal ‘data1’ is ‘u’, and ‘Ts’ is as I described it.


Ill ch
Ill ch on 2 Nov 2019
thank you very much for detailed useful information. Yesterday i was thinking on this problem. I found one solution :
for example:
Input signal: Ts= 0.0000733
After resmapling Output signal Ts= 0.00007
I took the round figure for both Ts=0.00007. I do not know either it is possible in research work but i feel that is the solution which i can do. Your comment will be helpful for me on rounding the Ts.
Star Strider
Star Strider on 2 Nov 2019
It may not be necessary to round it. In any event, if you want to, the easiest way to create it with:
Ts = 0.00007
is likely to use resample with
p = 700
q = 733
or the reverse of these, depending on what you started with and what you want as an output.

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