Tracking Control for an Overactuated Hypersonic Air-Breathing Vehicle with Steady State Constraints (PREPRINT)

The development of an air-breathing hypersonic vehicle employing scramjet propulsion is an ongoing research endeavor. Because of high velocity (>Mach 5), length and positioning of the engine, and relative sleekness, the flexibility of the vehicle is significant and there are strong couplings between thrust and pitch . As a result, control design for such a vehicle is a challenge. In previous works, linear controllers have been designed for a model of the longitudinal dynamics of a specific air-breathing vehicle possessing the same number of inputs and outputs. In this paper we consider a control design for the same vehicle model, but we restrict our attention to controlling only two outputs, namely the altitude and velocity, while we employ as control inputs, the elevator deflection, total temperature change across the combustor and the diffuser area ratio of the combustor. The specific control problem addressed in the paper is the design of a controller that ensures asymptotic tracking of altitude and velocity reference trajectories, while using the redundancy in the inputs to optimize the performance in steady-state. As a matter of fact, since the system is not square, the steady state solutions that enforce perfect tracking are nonunique. The controller employs a parameterization of all possible steady state trajectories that is used for optimization of the steady state input while providing perfect tracking and fulfilment of constraint on the magnitude of the control input. Simulations results are provided to validate the proposed approach.