Further results on adaptive control design for non-minimum phase air-breathing hypersonic vehicles

Air-breathing hypersonic vehicles may exhibit non-minimum phase behavior when altitude is selected as regulated output. This prohibits the use of inversion based control techniques. These vehicles are also subject to parametric uncertainties and un-modeled dynamics related to flexible effects of the fuselage. In this paper, we present an adaptive control method that achieves asymptotic set-point tracking in both airspeed and altitude using thrust and elevator deflection as the only control inputs. The non-minimum phase problem is overcome through output redefinition, where the altitude and flight-path angle dynamics are embedded in the resulting internal dynamics, together with appropriate integral error. The internal dynamics are then stabilized by saturating the interconnections and exploiting local stability properties. The adaptive controller for the attitude dynamics uses a pitch-rate observer combined with projection. This decouples the parameter estimation errors from internal dynamics, allowing for asymptotic set-point tracking in altitude. Simulation results on a simulation model with flexible effects are included to demonstrate the effectiveness of the proposed approach.