Design of Flutter Suppression Controllers for a Wing in Compressible Flow Based on High-Fidelity Aerodynamics

Abstract

Since active flutter suppression technologies could lead to more efficient aircraft, they are acquiring increasingly importance and research activities relying on wind tunnel demonstrators are flourishing to gain experience and knowledge. Aeroelastic models employed for control activities are traditionally based on Generalized Aerodynamic Forces (GAFs) computed through DLM in reduced frequency domain. The main limitation of this approach is that compressible flow exhibits nonlinearities which are not captured by DLM. To overcome this short coming, this paper solves the governing equations of motion in time domain coupling a structural dynamic solver and CFD Euler aerodynamics. The aeroelastic system is excited to identify the CFD GAFs which are coupled with the structural matrices yielding a more accurate state space realization of the aeroelastic system suited for control design activities. The state space realizations are then exploited to design H infinity-based flutter suppression controllers, which are implemented in the fully coupled computational fluid/structural dynamics solver to demonstrate the damping augmentation capabilities of the compensators. The approach is demonstrated on a realistic aeroelastic system and comprehensive nonlinear computations using controllers synthesized based on GAFs either computed via Euler CFD or uncorrected DLM are presented. Differences in the results, even at subsonic Mach numbers, will be explained based on comparative analyses of the different pressure fields, highlighting the benefits of using high-fidelity aerodynamics.