Flutter Suppression of Bridge Deck Section Using Controllable Winglets Driven by LQR Control

Active flutter control of bridge deck section using controllable winglets is studied. Self-excited wind forces acting on deck and winglets are modeled using the Scanlan-Tomko model. Vertical, lateral and torsional degrees of freedom are considered for deck and corresponding eighteen experimental flutter derivatives (FD) are used. Winglets are modeled as flat plates and FDs are obtained from Theodorsen functions. Time domain formulation using Rogers rational function approximation leads to divergence speed much lower than the actual one, which is confirmed by Quasi steady theory. Hence, for control study, the usual trial and error method involving sweeping through speed and frequency is used. Rotations of winglets relative to deck are considered as control input, rather than the driving torque. Full state feedback with LQR control is applied. The state variables are estimated by designing a full order observer system using pole placement technique. Winglet rotations being restricted within bounds, the flutter behavior is studied using closed loop responses and compared with eigenvalue analysis. Numerical results shows the implemented control strategy is quite effective in flutter suppression and enhancing the flutter speed.