Adaptive, suboptimal and nonlinear control of an aeroelastic system

In this thesis, control systems are designed for the flutter control of a nonlinear aeroelastic system. The aeroelastic model describes the plunge and pitch motion of a wing. The model includes plunge and pitch nonlinearties, and has a single control surface for the purpose of control. First an output feedback modular adaptive control system is derived. Quasi-steady aerodynamic model is used for the output feedback modular adaptive control system. For the synthesis of the adaptive controller, it is assumed that only pitch angle and plunge displacement are measured. The control system consists of an input-to-state stabilizing controller and a passive identifier. The passive identifier provides estimates of parameters for synthesis. The second control system is based on the state dependent Riccati equation method. This design yields a suboptimal control law. Finally a nonlinear controller based on backstepping design is presented. Unsteady aerodynamic model is used for the design of the suboptimal controller using state dependent Riccati equation approach and nonlinear controller using backstepping design technique. The unsteady aerodynamic is modeled with an approximation to Theodorsens theory. For the synthesis of second and third control systems, an observer is designed for estimating the unavailable states variables. Simulation results for each controller are presented. These results show that the designed control systems are effective in flutter suppression.