Heuristic Order Reduction of NARX-OBF models Applied to Nonlinear System Identification

Elder Oroski (Federal University of Technology of Paraná (UTFPR), Avenida Sete de Setembro 3165, 80230-901, Curitiba-PR, Brazil.)
Beatriz Pês (Federal Institute of Paraná (IFPR), Rua Engenheiro Tourinho, 829, Campo Largo-PR, Brazil)
Adolfo Bauchspiess (University of Brasília (UnB), Campus Darcy Ribeiro, Asa Norte, Brasília-DF, Brazil.)
Marco Antonio Freitas do Egito Coelho (University of Brasília (UnB), Campus Darcy Ribeiro, Asa Norte, Brasília-DF, Brazil.)

Article ID: 1341

Abstract


Nonlinear system identification concerns the determination of the modelstructure and its parameters. Although the designers often seek the bestmodel for each system, it can be tricky to determine, at the same time, thebest structure and the parameters which optimize the model performance.This paper proposes the use of a Genetic Algorithm, GA, and the Levenberg-Marquardt, LM, method to obtain the model parameters, as well asperform the order reduction of the model. In order to validate the proposedmethodology, the identification of a magnetic levitator, operating in closedloop, was performed. The class NARX-OBF, Nonlinear Auto Regressivewith eXogenous input-Orthonormal Basis Function, was used. The use ofOBF functions aims to reduce the number of terms in NARX models. Oncethe model is found, the order reduction is performed using GA and LM, ina hybrid application, capable of determining the model parameters and reducing the original model order, simultaneously. The results show, considering the inherent trade-of between accuracy and computational effort, theproposed methodology provided an implementation with good mean squareerror, when compared with the full NARX-OBF model.

Keywords


NARX-OBF Models;Genetic Algorithm;Levenberg Marquardt;System identification

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DOI: https://doi.org/10.30564/ssid.v1i2.1341

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