Aeroservoelasticity Interactions Studies on a Business Aircraft

Abstract

Multidisciplinary aeroservoelastic interactions are studied by combination of knowledge acquired in two main disciplines: aeroelasticity and servo-controls. In aeroelasticity, the Doublet Lattice Method DLM is used to calculate the unsteady aerodynamic forces Q(k, M) for a range of reduced frequencies k and Mach numbers on a business aircraft in the subsonic flight regime by use of Nastran software. For aeroservoelasticity studies, there is the need to conceive methods for these unsteady aerodynamic forces Q(k, M) conversions from frequency into Laplace domain Q( s ). Three methods are used for this type of conversion in the aircraft industry. These methods are: Least Square LS, Matrix Pade MP and Minimum State MS. A new method different from these three methods is presented, in which Chebyshev polynomials theories and their orthogonality properties are applied. In this paper, a comparison between flutter results expressed in terms of flutter speeds and frequencies obtained with our method with flutter results obtained with classical Pade and Least Squares methods is here presented for a business aircraft at one Mach number and a range of reduced frequencies. It has been found that results obtained with our method are better in terms of average error than results obtained with the two classical methods here presented.