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Parameter Estimation of Time Varying State

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Daniel
Daniel on 1 Aug 2011
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Edited: Ahmad Gadon 16 Sep 2021
I have a state space grey box model for which I have been using the PEM tool to determine one term in the state matrix for a given set of test data. The limiation I am finding with using the PEM tool is that the state has to be constant throughout the entire set of test data. I am looking for a way to determine the state as a function of time (the state is actually dependent on several other known factors). In the end, I am looking to determine the state vs. time so that I can generate a lookup table for the state as a function of the other known inputs.

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Answers (1)

Rajiv Singh
Rajiv Singh on 1 Aug 2011
Do you mean that the state-space matrices A,B,C,D are time dependent? If so, please look into the "nonlinear grey box" modeling technique:
//www.tianjin-qmedu.com/help/toolbox/ident/ug/bqs6lf8.html
In: //www.tianjin-qmedu.com/products/sysid/demos.html ,
see: "Tutorials on Nonlinear Grey Box Model Identification"
Unlike the linear grey box (idgrey) case, the ODE function of a nonlinear grey box model (idnlgrey) takes in the current time instant t, input u(t) and state value x(t) as regular input arguments. Hence you can create a dependency of parameters on time values.
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Ahmad Gad
Ahmad Gad on 16 Sep 2021
Can you explain this more? None of the links work.

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