Aerodynamic Forces Approximations using the Chebyshev Method for Closed-Loop Aero-servoelasticity Studies

The approximation of unsteady generalized aerodynamic forces from the frequency domain into the Laplace domain acting on a Fly-By-Wire aircraft presents an important challenge in the aero-servoelasticity area. The aerodynamic forces in the reduced-frequency domain are approximated in the Laplace domain, to be able to study the effects of the control laws on the flexible aircraft structure. In this paper, we present a new method for the approximation of the generalized aerodynamic forces by use of Chebyshev polynomials and their orthogonality properties. A comparison of this new method with the Pade method used to calculate an approximation of the generalized aerodynamic forces from the frequency domain into the Laplace domain is presented. This comparison shows that this new method gives excellent results with respect to the Pade method and is applied on the Aircraft Test Model from NASA Dryden Flight Research Center.

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