A flutter suppression active controller

Abstract

Flutter is a dynamic aeroelastic instability that involves the interaction of aerodynamic, elastic, and inertial forces. This instability may occur in aircraft surfaces, like wings and tails, leading them to a divergent oscillatory motion. A classical two-degrees-of-freedom flutter is an interaction of bending and torsional modes of vibration of a structure. A flexible mount system has been developed for flutter tests with rigid wings in wind tunnels. This flexible mount has to provide a well-defined two-degrees-of-freedom system on which rigid wings encounter flutter. Active control schemes for flutter suppression can be tested using this experimental set-up. An aeroelastic model is formulated to simulate the aeroelastic behaviour of this system. The equations of motion are developed using Lagrange' equations and the Principle of Virtual Work, resulting in a state space representation. This is a convenient way to determine pitch and plunge time responses for several initial conditions and velocities. Using this model, a state feedback controller of the form u = – Kx is determined. The wind tunnel model is a rectangular wing with a NACA 0012 airfoil section and a trailing edge control surface as actuator. The main goal is to suppress flutter and to maintain the stability of the closed loop system.