Adaptive Fuzzy Sliding Mode Controller Design Using a High-Gain Observer for a Nonlinear Aeroelastic System under Unsteady Aerodynamics

In this paper, an adaptive fuzzy sliding mode controller utilizing a high-gain observer is proposed to address the aeroelastic instabilities of a novel nonlinear aircraft wing section under unsteady aerodynamics. The controller is designed to effectively mitigate high amplitude oscillations that arise in the system and enable aircraft to operate within an extended flight envelope. Additionally, the proposed controller utilizes output feedback to estimate the states and nonlinear dynamics of the model. The two-degree-of-freedom (2-DOF) nonlinear aeroelastic system describes the pitch and plunge motions of the wing section equipped with trailing and leading edge control surfaces. The resulting aeroelastic model, including the structural stiffness nonlinearities and the unsteady aerodynamic model, is based on Wagner's indicial function. The simulation results demonstrate the effectiveness of the suggested controller in suppressing the flutter phenomenon and improving the flight speed range. Further, the proposed controller accurately estimates the states of the model and successfully drives them to the origin despite the presence of disturbances and uncertainties.