Aeroservoelasticity Analysis Method Based on an Error Analytical Form Applied on a Business Aircraft

Abstract

Aeroservoelasticity is a multidisciplinary study that combines the following disciplines: aerodynamics, aeroelasticity and servo-controls. For aeroelasticity studies, the Doublet Lattice Method (DLM) is used to calculate the aerodynamic unsteady forces for a set of reduced frequencies k and Mach numbers M on a business aircraft in the subsonic flight regime. There are three classical methods in the aeroservoelasticity used to approximate these forces Q (k, M) by rational functions in the Laplace domain Q(s): Least Square (LS), Matrix Padé (MP) and Minimum State (MS). A new method called Corrected Least Square (CLS) is presented. This new method uses an analytical form of the error as a function of Laplace variable similar to the analytical form of the aerodynamic forces calculated by use of the LS method. The new CLS method does not take additional time to the computation of the unsteady aerodynamic forces when compared to the LS method, and the aerodynamic forces calculated with the CLS method are closer to the aerodynamic forces data in the frequency domain than the aerodynamic forces calculated by the standard LS method. The new CLS method applied on a business aircraft gives better results (flutter speeds and frequencies) and faster (as it uses smaller number of lag terms) than the LS method.