in the present paper, the aeroelastic stability of helicopter rotor blade is determined using aeroelastic frequency response function. the aeroelastic model of blade is obtained by combining dowell - hodges beam model with loewy unsteady aerodynamic theory which considers an unsteady wake beneath the rotor. equations are formed and aeroelastic frequency response functions are obtained by invert...

High-aspect-ratio wings present in very flexible aircraft can undergo large deformations, which results in significant changes in natural frequencies as well as in static and dynamic aeroelastic response. This geometric nonlinear behavior becomes an integral part of any aeroelastic analysis to be conducted in such class of vehicles. Aeroelastic scaling is an important way to study the aeroelast...

This paper introduces an adaptive flutter suppression control algorithm which is based on the iterative estimate of the aeroelastic plant and design of the feedback controller. In this algorithm, the dual-Youla parametrization is implemented as an essential part to estimate the open loop aeroelastic model from the closed loop experiment. The advantage of utilizing the dual-Youla parametrization...

In the present paper, the aeroelastic stability of helicopter rotor blade is determined using Aeroelastic Frequency Response Function. The conventional methods of aeroelastic stability usually use an iterative procedure while the present method does not require such approach. Aeroelastic Frequency Response Functions are obtained by inverting dynamic stiffness matrix of the aeroelastic system. S...

A very flexible unmanned aerial vehicle has been designed and manufactured at the University of Michigan. The vehicle is named X-HALE, whose flight tests are expected to provide important data of its geometrically nonlinear aeroelastic behavior coupled with the six rigid-body degrees of freedom. As the target of the aeroelastic design, the X-HALE vehicle will present unstable aeroelastic/flight...

The ‘‘stick’’ type aeroelastic model, referred to here as ‘‘aeroelastic balance,’’ has served as an effective tool for investigating wind-induced response of tall buildings and towers in both fundamental research as well as design applications. However, some questions still remain unaddressed in the available literature regarding the efficacy of the aeroelastic balance as a design tool. These c...

Two 2-D aeroelastic models are presented here to determine instability boundary (flutter speed) and gust response of a typical section airfoil with degrees of freedom in pitch and plunge directions. To build these 2-D aeroelastic models, two different aerodynamic theories including Indicial Aerodynamic Theory and Vortex Lattice Method (VLM) have been employed. Also, a 3-D aeroelastic framework ...

Methods for structural design, control, and testing of flexible aircraft structures are considered. Focus is on nonconventional aircraft configurations and control concepts. The interaction between analysis and testing is a central topic and all studies include validation testing and comparison between computational and experimental results. The first part of the thesis is concerned with the de...

This work presents the analysis of nonlinear aeroelastic time series from wing vibrations due to airflow separation during wind tunnel experiments. Surrogate data method is used to justify the application of nonlinear time series analysis to the aeroelastic system, after rejecting the chance for nonstationarity. The singular value decomposition SVD approach is used to reconstruct the state spac...

The problem of the determination of the subcritical aeroelastic response and flutter instability of nonlinear two-dimensional lifting surfaces in an incompressible flow-field via Volterra series approach is addressed. The related aeroelastic governing equations are based upon the inclusion of structural nonlinearities, of the linear unsteady aerodynamics and consideration of an arbitrary time-d...