Nonlinear adaptive control for lateral dynamics with fixed roll angle of hypersonic vehicles at subsonic speeds

Hypersonic vehicles are complex nonlinear systems with uncertain dynamics. This work presents a robust nonlinear adaptive (NA) control system for the operation of these vehicles at subsonic speeds. The complexity of the dynamic system is considered in the design, in order to address robustness issues. In this work, we only consider lateral dynamics with a fixed roll angle (five degree of freedom, or 5-DOF). These dynamics are divided into subsystems for aircraft speed, flight-path angle, and yaw angle. A robust NA control design is implemented to provide asymptotic tracking regulation of these output quantities. Adaptation is employed in this study because of its robustness properties. The stability analysis is performed based on a Lyapunov function for the feedback closed-loop system. Simulations of the design indicates that it successfully provides flight control.