Sliding Mode Control for a Nonlinear Aeroelastic System through Backstepping

This paper considers an aeroelastic two-dimensional wing-flap system with uncertainty and external disturbance. Nonlinear stiffness in pitch is expressed as the second-order polynomial form. In the uncontrolled aeroelastic model, limit cycle oscillation (LCO) appears at postflutter speed. By utilizing leading-edge and trailing-edge control surfaces as the control input, a sliding mode control scheme using varying boundary layers based on backstepping design is developed to suppress aeroelastic vibration. The proposed control strategy combines the advantages of both sliding mode control with varying boundary layers and backstepping technique. In contrast to the conventional sliding mode control design, the proposed method not only avoids chattering but also obtains stronger robustness. The results of numerical simulation clearly demonstrate the effectiveness of the proposed control strategy for aeroelastic vibration suppression under saturated controller input.