Active Flutter Suppression for a T-Tail via Optimal Control

Abstract

A new generation of transport aircraft increasingly adopts T-tail configurations for their excellent aerodynamic, operating, and structural performance. However, flutter of T-tail configurations is a serious dynamic instability problem caused by aerodynamic and structural interactions between the vertical stabilizer and the horizontal stabilizer. The horizontal tailplane (HTP) is mounted on the vertical tailplane (VTP). Bending and twisting of the VTP induce rolling, yawing, and in-plane motion of the HTP, which has a significant effect on T-tail flutter. In this paper, a multiple input/multiple output (MIMO) linear quadratic Gaussian (LQG) controller is designed to suppress flutter for a T-tail. The state-space equations of the aeroservoelastic (ASE) T-tail model, which are composed of the state-space equations of the aeroelastic system and the actuator dynamics, are derived for the design of the control law. The controller is synthesized by posing and solving a weighted optimization problem with the goal of making the rudders collaborate deflection for flutter mode suppression and expand the boundary of the T-tail flutter. A thorough analysis of the performance achieved by the closed-loop system was performed through numerical simulations. The numerical results demonstrate that the proposed LQG controller can effectively suppress the T-tail flutter and expand the flutter boundary.