Implementação de controle ativo para supressão de flutter de uma seção típica bidimensional

Abstract

A design methodology for an active control system used to suppress flutter in aeroservoelastic systems is presented. Flutter is a dynamic aeroelastic instability phenomenon, hose oscilatory motion presents self-excitation due to the dynamic coupling between any two elastic modes of the system. This instability occurs from a certain velocity, called the flutter velocity, in which the oscillations become divergent from the equilibrium point of the system, featuring an unstable movement. Due to the destructive characteristic of flutter, design restrictions are adopted to prevent the flutter velocity from being within the operational envelope. Even in operations at speeds below flutter, but close enough, damage to flight performance may occur due to high vibration of the structure. To mitigate the effects of this phenomenon on aircraft design and operation, an active flutter suppression system can be adopted, which consists of designing a control law to act on the system by regulating the structure’s vibration in order to suppress the flutter. It is in this context that the present work fits: Develop a AFS for a two-dimensional wing cross section with a control surface located on the section’s trailing edge. A technique known as RFA is used to describe the reduced frequency-dependent aerodynamic loads in the time domain, in which four delay poles are assumed to represent the nonstationary effects of the aerodynamics. The mathematical model is described using a state-space representation. The control system was designed using this model via quadratic linear regulator methodology to design the state feedback gain. The estimated flutter velocity for the studied system is found to be 29,59 m/s, which indicates a percentage error of 2% when compared to values from literature, showing the adequacy of the methodology implemented. Furthermore, the results obtained shows the ability of the proposed closed-loop structure to stabilize the system in the design condition, determined as the point of dynamic instability of the open-loop system. As a consequence, it can also be seen an increase in the flutter speed of the closed-loop system, although there is no theoretical guarantee for this.