Altitude and Velocity Tracking Control for an Airbreathing Hypersonic Cruise Vehicle

Abstract

This paper describes an adaptive linear quadratic (ALQ) altitude and velocity tracking control algorithm for the longitudinal model of a generic airbreathing hypersonic flight vehicle hypersonic flight vehicle. The vehicle design is inspired by a set of mission requirements broadly accepted for a hypersonic cruise vehicle intended for both space access and military applications. The vehicle, CSULA-GHV, has an integrated airframe-propulsion system configuration and resembles an actual test vehicle. The complete aerodynamic and scramjet engine data including the coupling between the two have been developed by both flow theoretic models and by using an integrated aero-propulsion CFD model in FLUENT. A set of nonlinear longitudinal equations of motion for the vehicle which include both an inverse square law, gravitational model and the centripetal acceleration as well as the CFD-generated aerodynamic, propulsion, and coupled aeropropulsion data are developed and used for control design. The certainty equivalence principle is used to combine the adaptive law with the control structure of the standard linear quadratic (LQ) problems. The aerodynamics of the AHFV is linearized at different trimmed conditions, and the traditional gain scheduling LQ design is also implemented. Simulation results demonstrate the effectiveness of ALQ control design in tracking altitude and velocity commands over LQ design with gain scheduling, in that it can discern aerodynamics changes and adapt the control laws accordingly. This also helps the system to achieve fault-tolerance to control surface damage.