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Finite-state aerodynamic modelling for gust load alleviation of wing–tail configurations

Published online by Cambridge University Press:  04 July 2016

M. Gennaretti  and
C. Ponzi
M. Gennaretti
Affiliation:
University of Rome III, Dipartimento di Ingegneria Meccanica e Industriale via della Vasca Navale, Rome, Italy
C. Ponzi
Affiliation:
Alenia Difesa — Divisione Sistemi Missilistici, Italy
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Abstract

A finite-state aerodynamics methodology is proposed for the analysis of the forces generated by a gust. To illustrate and assess the methodology, gust-response and gust-alleviation applications are included. Finite-state aerodynamics denotes a technique to approximate aerodynamic loads so as to yield an aircraft model of the type ẋ = Ax + Bu (state-space formulation). In this paper, a finite-state formulation is proposed to include the presence of a gust. The aerodynamic loads to be approximated are evaluated here by using a frequency-domain boundary-element formulation; the flow is assumed to be irrotational except for a zero-thickness vortex layer (wake). The gust-alleviation application consists of determining a control law for reducing the response to a vertical gust disturbance, as measured by the centre of mass acceleration. Two optimal-control approaches are considered for the synthesis of the control law: one uses the classical linear-quadratic regulator (LQR), whereas the second includes the additional feed-forward of the gust velocity ahead of the aircraft. Deflections of ailerons and elevators are assumed to be the control variables. Numerical results deal with responses to both a deterministic ‘1 – cosine’ gust distribution and a stochastic von Kármán spectrum. They indicate that the finite-state aerodynamic model proposed is capable of approximating, with a high level of accuracy, both the aerodynamic loads induced by the aircraft kinematics variables and those induced by the control variables, over a wide frequency range.

Information

Type
Research Article
Information
The Aeronautical Journal , Volume 103 , Issue 1021 , March 1999 , pp. 147 - 158
Copyright
Copyright © Royal Aeronautical Society 1999 

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