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Nonlinear Aeroelasticity and Active Control of Airfoils Subjected to Gusts

Title:

Nonlinear Aeroelasticity and Active Control of Airfoils Subjected to Gusts

Zhang, Xiaoyang (2019) Nonlinear Aeroelasticity and Active Control of Airfoils Subjected to Gusts. Masters thesis, Concordia University.

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Abstract

In this thesis, the coupling effects of structural nonlinearities and a gust input on the aeroelastic behaviour of an airfoil are studied, and an adaptive controller which is effective for suppressing limit-cycle oscillations (LCOs) is designed. The dynamics of the airfoil are approximated via two- (pitch and plunge) and three-degree-of-freedom (pitch, plunge and flap) models. Different types of structural nonlinearities, such as free-play and hysteresis are considered in the modelling. The nonlinear dynamics is analyzed based on time history, power spectral density (PSD), phase-plane, and Poincar\'{e} section plots, along with the estimation of the dominant Lyapunov exponent for the chaotic-like motion. It is found that free-play and hysteresis nonlinearities may considerably reduce the critical flow velocity compared to the linear system. The dynamic responses of the nonlinear system to sharp-edged and 1-cosine gust profiles are obtained at different flow velocities and compared to those of the system with no gust input. In addition, basin of attraction is plotted to show the stability boundary of the system subjected to a sharp-edged gust with various amplitudes. It is discussed that as the gust becomes stronger, the likelihood of the occurrence of LCO increases. Based on the nonlinear model with a control surface, the suppression of LCO is studied. Without uncertainties, a PD controller together with a partial feedback linearized controller can effectively alleviate oscillations due to gusts and structural nonlinearities. Considering some uncertain structural parameters, an adaptive controller with estimation parameter update law is further designed to stabilize the system. A Lyapunov function is constructed and utilized to prove the stability of the system.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Mechanical, Industrial and Aerospace Engineering
Item Type:Thesis (Masters)
Authors:Zhang, Xiaoyang
Institution:Concordia University
Degree Name:M.A. Sc.
Program:Mechanical Engineering
Date:22 November 2019
Thesis Supervisor(s):Xie, Wen-Fang and Kheiri, Mojtaba
ID Code:986183
Deposited By: Xiaoyang Zhang
Deposited On:26 Jun 2020 13:45
Last Modified:26 Jun 2020 13:45
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