First order transfer function system identification
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I am doing this open loop test in which I am adding constant 561 to every measured output value from the process model and then exporting it for it to be used in model identification.
input is the step response of final value 1.54 and output is the simout cell values in schematic.
In SYSID after estimating first order TF model, fitting is very low(16%). It is passing residual test though.The equation of the model estimated :-
I tried after preprocessing(removing detrends) but the equation of First order TF model estimated after that was way off from this process model used in schematic.
When I used only 29/4s+1 as process model( i.e. not adding 561 to its output) using same procedure in SYSID then 100% fittng model passing residual tests was estimated(without any preprocessing).
Why adding a constant is making such a big difference? Is my process wrong ? How to solve this problem?
Any help would be appreciated.
Thanks in advance:)
3 Comments
Mathieu NOE
on 30 Nov 2020
again
I would personnaly not make things too complicated and especcially remove constants on the output and add that later on , once the model fit is validated
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