Optimal control law synthesis for flutter suppression using active acoustic excitations

Abstract

This paper describes a development of the optimal control law design procedure for the flutter suppression of airfoils using active acoustic excitations. A bending-torsion typical section and a two-dimensional incompressible aerodynamic model are adopted for the present analysis. An irreducible state-space description of the aeroservoelastic system is constructed via the use of Hankel matrices and the singular value decomposition method. The evaluation of the degree of controllability/observability and the synthesis of the optimal control law using steady-state linear quadratic regulator theory accompanied by an asymptotic state observer are performed. This optimal control law design enables the search of the most effective position to locate the sound wave generator. The trailing edge is shown to be the best region for installing the sound wave generator, where the highest degree of controllability and the minimal control effort are attained. A case study shows that approximately 20 dB reduction in sound pressure level can be achieved using this optimal control law design.