METHOD BASED ON THE LS APPROACH USED FOR FLUTTER AEROSERVOELASTICITY ANALYSIS STUDIES

摘要

Aeroservoelasticity study is a multidisciplinary study of three main disciplines: unsteady aerodynamics, aeroelasticity and servo-controls. For aeroelasticity studies, the Doublet Lattice Method DLM is used to calculate the aerodynamic unsteady forces Q(k, M) for a set of reduced frequencies k and Mach numbers on a business aircraft in the subsonic flight regime. In these studies, three classical methods are used to approximate these unsteady generalized forces Q(k, M) by rational functions in the Laplace domain Q(s{top}-): Least Square LS, Matrix Pade MP and Minimum State MS. In this paper, we present a new method, which uses an analytical form of the error as function of Laplace variable s similar to the analytical form of the aerodynamic forces calculated by use of the Least Square LS method. The results obtained by this method are compared to the results obtained by the LS method as this new method CLS is based on the LS approach. We found that the use of the new method does not include an additional time for the computation of unsteady aerodynamic forces with respect to the LS method. We found that new method aerodynamic forces are closer to the aerodynamic forces data in the frequency domain Q(k) than the aerodynamic forces calculated by the standard LS method. We applied this new method to an existing business aircraft and we found that our method here presented gives between 33% and 99% reduction rate in comparison with the LS method.