Nonlinear control of a hypersonic vehicle with structural flexibility

The design of a nonlinear robust adaptive controller for a flexible air-breathing hypersonic vehicle model is considered in this work. Due to the complexity of a first-principle model of the vehicle dynamics, for design and stability analysis a simplified model is adopted, which nonetheless retains the dominant features of the higher fidelity model, including non-minimum phase behavior, flexibility effects and strong coupling between the engine and flight dynamics. A combination of nonlinear sequential loop-closure and adaptive dynamic inversion is adopted to design a dynamic state-feedback controller that provides stable tracking of velocity and altitude reference trajectories and imposes a desired setpoint for the angle of attack. The proposed methodology addresses the issue of robustness with respect to both parametric model uncertainty, which naturally arises in adopting reduced-complexity models for control design, and dynamic perturbations due to the flexible dynamics. Simulation results on the full nonlinear model are included to show the effectiveness of the controller.