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

Zhi-Sai Ma,Xin Zhang,Bo Wang,Qian Ding

doi:10.1155/2019/3978260

Abstract

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.

Highlights

Folding fins are widely adopted in missiles for the efficient use of space during storage and transportation
The nonlinear dynamic characteristics of a folding fin are experimentally analyzed by using identification approaches
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

Summary

Introduction

Folding fins are widely adopted in missiles for the efficient use of space during storage and transportation. Two- or three-degree-of-freedom airfoils with freeplay nonlinearity were generally used to reveal nonlinear phenomena and validate corresponding nonlinear analysis methods [3,4,5,6, 9, 10]. These studies can offer useful insights into what is happening to the folding structures with freeplay, but they cannot be directly used to solve practical engineering problems, as real folding structures are flexible components with more degrees of freedom. In most cases the types and values of nonlinear characteristics of the hinges are unknown and difficult to obtain

Methods

Results

Conclusion