L1 adaptive control of a nonlinear aeroelastic system despite gust load

The development of a control system for the suppression of aeroelastic vibration of a two-dimensional nonlinear wing-flap system based on the L-1 adaptive control theory is the subject of this paper. The prototypical aeroelastic wing section model considered here includes structural nonlinearity, parameter uncertainties and gust loads. For the purpose of control, a single trailing-edge control surface is used. The uncontrolled aeroelastic model exhibits limit cycle oscillations beyond a critical free-stream velocity. An L-1 adaptive law is developed for the suppression of aeroelastic oscillations using the pitch angle and pitch rate feedback. The control system includes a state predictor. The adaptation gain and the parameter of a filter are properly chosen to satisfy desirable performance bounds on the system trajectories. Simulation results are presented which show that the control system suppresses the oscillatory responses of the system in the presence of large parameter uncertainties and triangular, sinusoidal, and exponential gust loads.