scholarly journals Nonlinear System Identification of Folding Fins with Freeplay Using Direct Parameter Estimation

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Zhi-Sai Ma ◽  
Bo Wang ◽  
Xin Zhang ◽  
Qian Ding
Keyword(s):  
Parameter Estimation ◽  
System Identification ◽  
Nonlinear System ◽  
A Priori ◽  
Nonlinear System Identification ◽  
Estimation Method ◽  
Nonlinear Behavior ◽  
Significance Test ◽  
Nonlinear Dynamic Model ◽  
Assembly Error

Folding fins are widely adopted in missiles for the efficient use of space during storage and transportation, while nonlinear behavior of freeplay is inevitable due to the factors such as mismachining tolerance, assembly error, and abrasion. The problem of nonlinear system identification of folding fins with freeplay is considered in this paper. A direct parameter estimation method which can identify the nonlinear system with freeplay under base excitation is proposed and subsequently applied to establish the nonlinear dynamic model of a folding fin. The best set of coefficients is selected by using the significance test, allowing the proposed method to detect and locate the most relevant nonlinearities of the practical structure. Experimental results demonstrate that the proposed method is able to decouple the linear and nonlinear dynamics of a nonlinear structure and estimate natural frequencies of the derived linear system along with nonlinear internal forces in one computational step, even if no a priori knowledge of the type of nonlinearities is given.

scholarly journals A Multiple-Model Approach for Synchronous Generator Nonlinear System Identification

2012 ◽  
Vol 63 (4) ◽  
pp. 249-254 ◽  
Author(s):  
Seyed Ahmadi ◽  
Mehdi Karrari
Keyword(s):  
System Identification ◽  
Nonlinear System ◽  
Nonlinear System Identification ◽  
Nonlinear Behavior ◽  
Synchronous Generator ◽  
Operating Conditions ◽  
Model Complexity ◽  
Multiple Model ◽  
Local Models ◽  
Model Approach

A Multiple-Model Approach for Synchronous Generator Nonlinear System Identification In this paper, a multiple model approach is proposed for the identification of synchronous generators. In the literature, the same structure often is used for all local models. Therefore, to obtain a precise model for the operating condition of the synchronous generator with severely nonlinear behavior, many local models are required. The proposed method determines the complexity of local models based on complexity of behavior of the synchronous generator at different operating conditions. There are two choices for increasing model precision at each iteration of the proposed method: (i) increasing the number of local models in one region, or (ii) increasing local model complexity in the same region. The proposed method has been tested on experimental data collected on a 3 kVA micro-machine. In the study, the field voltage is considered as the input and the active output power and the terminal voltage are considered as the outputs of the synchronous generator. The proposed method provides a more precise model with fewer parameters compared to some well known methods such as LOLIMOT and global polynomial models.

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