Skip to main content
Top

2015 | Book

Aeroservoelasticity

Modeling and Control

insite
SEARCH

About this book

This monograph presents the state of the art in aeroservoelastic (ASE) modeling and analysis and develops a systematic theoretical and computational framework for use by researchers and practicing engineers. It is the first book to focus on the mathematical modeling of structural dynamics, unsteady aerodynamics, and control systems to evolve a generic procedure to be applied for ASE synthesis. Existing robust, nonlinear, and adaptive control methodology is applied and extended to some interesting ASE problems, such as transonic flutter and buffet, post-stall buffet and maneuvers, and flapping flexible wing.

The author derives a general aeroservoelastic plant via the finite-element structural dynamic model, unsteady aerodynamic models for various regimes in the frequency domain, and the associated state-space model by rational function approximations. For more advanced models, the full-potential, Euler, and Navier-Stokes methods for treating transonic and separated flows are also briefly addressed. Essential ASE controller design and analysis techniques are introduced to the reader, and an introduction to robust control-law design methods of LQG/LTR and H2/H∞ synthesis is followed by a brief coverage of nonlinear control techniques of describing functions and Lyapunov functions. Practical and realistic aeroservoelastic application examples derived from actual experiments are included throughout.

Aeroservoelasiticity fills an important gap in the aerospace engineering literature and will be a valuable guide for graduate students and advanced researchers in aerospace engineering, as well as professional engineers, technicians, and test pilots in the aircraft industry and laboratories.

Table of Contents

Frontmatter
1. Aeroservoelasticity
Abstract
This chapter introduces aeroservoelasticity as a discipline, and highlights its historical evolution into a necessary concept in modern aircraft design. A simple example is used to illustrate the principles of aeroservoelastic modeling, control law derivation, and closed-loop analysis.
Ashish Tewari
2. Structural Modeling
Abstract
This chapter presents details of deriving a structural dynamics model for use in aeroelastic and aeroservoelastic applications. Beginning with an introduction on assumptions and idealizations required for modeling aircraft structures, the principles of static load-displacement relations, flexibility influence coefficients, virtual work, strain energy, and stiffness influence coefficients are described. For the dynamic case, the structural dynamics equations are derived from both Lagrange’s energy approach and Newton’s laws. A large part of the chapter presents the various discretization schemes for structural modeling. These include the lumped parameter approximation, the finite-element method, and the Rayleigh-Ritz method. Emphasis is placed on the finite element method, with details of Euler-Bernoulli beam-shaft model of two-noded elements for high aspect-ratio wings, and the Poisson-Kirchoff (CPT) plate theory for low aspect-ratio wings with triangular and rectangular elements.
Ashish Tewari
3. Unsteady Aerodynamic Modeling
Abstract
This chapter details the various methods of deriving an unsteady aerodynamic model for aeroservoelastic analysis. This usually takes the form of a linear operational relationship between pressure distribution and upwash distribution on a lifting surface for subsonic and supersonic flows, and a nonlinear partial differential equation (Euler, full-potential, or transonic small-disturbance equation) for transonic flows. The treatment of the flow models for inviscid as well as viscous flows, and for various speed regimes is presented. Detailed derivations include the incompressible vortex-lattice methods, analytical models, Green’s integral formulations, velocity potential and acceleration potential integral equations for compressible subsonic and supersonic flows, and transonic small-disturbance models. Numerical schemes are described in detail for subsonic Doublet-Lattice, supersonic Mach-Box, supersonic Doublet-Point, and transonic Doublet-Lattice methods.
Ashish Tewari
4. Finite-State Aeroelastic Modeling
Abstract
Chapter 4 describes the finite-state modeling techniques for deriving a linear, time-invariant state-space model of the aeroservoelastic plant. The linear systems theory is applied to the aeroelastic system in order to convert the frequency domain unsteady aerodynamics to the time domain. This requires the use of rational function approximations (RFA) in the Laplace domain for analytic continuation from harmonic curve-fits to transient response aerodynamics. The chapter presents the various RFA models, which have been developed and optimized by both gradient and non-gradient, nonlinear optimization techniques. Application of the RFA method to both typical wing section, and three-dimensional wing, with control surfaces, is presented. Illustrative finite-state model is presented for the flutter analysis of a real aircraft wing with experimental structural data, and compared with flight-flutter test results.
Ashish Tewari
5. Linear Aeroelastic Control
Abstract
Chapter 5 presents the linear control theory for designing and analyzing aeroservoelastic systems. Basic concepts of linear feedback regulator, stochastic state estimation, linear optimal control, and robust multivariate control are highlighted, and their applications to adverse aeroservoelastic interactions, active flutter suppression and load alleviation are illustrated by realistic examples. Treatment of control design methods includes Hamilton-Jacobi-Bellman and Euler-Lagrange formulations, linear, quadratic regulator, Kalman filter, linear quadratic Gaussian compensator, loop-transfer recovery, and \(H_2/H_{\infty}\) synthesis.
Ashish Tewari
6. Nonlinear Aeroservoelastic Applications
Abstract
The final chapter of the book is a culmination of the discussion on aeroservoelasticity in nonlinear analysis and design. Both the describing functions approximation and Lyapunov stability theorems for nonlinear and adaptive control law design are presented, with applications to flapping-wing flight, transonic flutter and buffet, and an illustrative example of adaptive suppression of transonic limit-cycle oscillations.
Ashish Tewari
Backmatter
Metadata
Title
Aeroservoelasticity
Author
Ashish Tewari
Copyright Year
2015
Publisher
Springer New York
Electronic ISBN
978-1-4939-2368-7
Print ISBN
978-1-4939-2367-0
DOI
https://doi.org/10.1007/978-1-4939-2368-7

Premium Partners