How can I add contraints to a model ( non linear arx, arx, armax ...) ?

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Nils B
Nils B 2019-8-4
回答： Nils B 2019-8-11
Hello,
I have a set of data which describes a temperature process. The dataset contains various temperatures from sensors and
the voltage input. I already estimated several models from the data, but I wondered if it is possible to add contraints
when I create the models? For example I would like to state that the minimum Temperature for all sensors is 25 degrees (since
that is room temperature). Is it possible to include that information to may model somehow?

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采纳的回答

Rajiv Singh
Rajiv Singh 2019-8-5
If the constraints can be expressed as lower or upper bounds on the model's parameters, the estimations routines will handle them. The process looks like:
  1. Create model template, e.g., sys = idss(...)
  2. Specify bounds on parameters; sys.Structure.<parameter>.Minimum = ...
  3. Identify the structured model: sys2 = <estimator>(data, sys)
For more complex constraints, such as parameter inter-relationships, you need to use the grey box modeling approach. See:
https://www.mathworks.com/help/ident/ug/estimating-coefficients-of-odes-to-fit-given-solution.html
https://www.mathworks.com/help/ident/ug/estimate-complex-conjugate-poles-and-zeros-using-grey-box-model.html

更多回答（1 个）

Nils B
Nils B 2019-8-11
Thanks for your answer, however your approach is not possible with non liniar ARX models, since they don't provide a property like idss models. Do you know a way to solve that, beside the grey model approach because the differntial equations of the system are not known?

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