Active flutter suppression of a two-dimensional airfoil based on sliding mode control method

Flutter, a dynamic instability of aircrafts, may degrade the safety of the structures. Active flutter suppression (AFS) is a considerable solution to this issue. Sliding mode control (SMC) method, a nonlinear control strategy, is applied to AFS of a typical two-dimensional airfoil in this work. The airfoil has a trailing-edge flap utilized for flutter control. The system involves a two-DOF (degree-of-freedom) motion whose equations are constructed by using quasi-steady aerodynamic forces. First, the AFS system is designed by state feedback SMC method to suppress the flutter. Then, a sliding mode observer (SMO) is incorporated for further improvements. Finally, classical Runge-Kutta (RK) algorithm is utilized for simulations. The results indicate that the SMO can estimate the system states fast. Combining with the SMO, the controller could suppress the flutter at 14.8% above the open-loop flutter boundary.