Nonlinear Adaptive Dynamic Inversion Applied to a Generic Hypersonic Vehicle

Flight control of hypersonic vehicles is challenging because of the wide range of operating conditions encountered and certain aspects unique to high speed flight. A particular safety concern in hypersonic flight is the risk of an inlet unstart, which not only produces a significant decrease in thrust but also results in a change to the aerodynamics and thus can lead to the loss of the vehicle. Previous work on control design for hypersonic vehicles often uses linearized or simplified nonlinear dynamical models of the vehicle, and very little work has been done on recovering from unstart events. Using a generic hypersonic vehicle as a control design and simulation model, this paper develops a nonlinear adaptive dynamic inversion control architecture with a control allocation scheme to track realistic flight path angle trajectories. A robustness analysis is performed on the initial control architecture design, which shows that the control architecture is able to handle time delays, perturbations in stability derivatives, and reduced control surface effectiveness. The control architecture then is evaluated for its ability to handle inlet unstart. Simulation results presented in the paper demonstrate that the approach achieves desired tracking performance while being robust to the particular uncertainties and inlet unstart conditions studied.