Model reference adaptive control of nonlinear aeroelasticity

The dynamic equations of a two-dimensional airfoil with leading and trailing edge control surfaces are described in state space. Then it is considered that there exists parametric uncertainty in the hysteresis nonlinearity in pitch. Based on Lyapunov stability theory, a structured model reference adaptive control law is designed. The simulation results show that the open-loop aeroelastic system is unstable and exhibits limit circle oscillation, while the closed-loop system reaches to stable state quickly. As the existence of hard constraint on the control inputs, the closed-loop system becomes unstable when the freestream velocity is higher. The effects of maximal control inputs on the closed-loop critical flutter velocity are investigated, and a stable boundary is obtained.