Guidance and control law design for missiles traveling at hypersonic speeds is an extremely difficult task due to the inherently coupled nonlinear nature of the system dynamics. The controller designs are further complicated by model uncertainty and unmodeled disturbances, which are inevitable in practical application. Beyond the challenges inherent in the system dynamics, additional complications arise in the design of hypersonic missile control laws, where terminal constraints are imposed in order to optimize target penetration. In this research, a robust nonlinear control technique is combined with an optimal control method to develop a control law for air-breathing hypersonic missiles in the presence of model uncertainty and unmodeled, nonlinear exogenous disturbances. The control law presented in this paper is designed to be computationally inexpensive, requiring no observers, online adaptive laws, or function approximators. One of the contributions of this research is detailed theoretical analysis of the performance characteristics of the proposed tracking control design. In addition, maximum target penetration is achieved by generating an optimal desired trajectory that incorporates terminal constraints in the cost function. Specifically, the trajectory optimization routine is designed to minimize angle of attack (AoA) and inertial angle of obliquity (AoO) at impact. A Lyapunov-based stability analysis is utilized to prove global asymptotic trajectory tracking, and high-fidelity numerical simulation results are provided to verify the practical performance of the proposed guidance law design.
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