Singular perturbation control of the longitudinal flight dynamics of an UAV

This paper presents a singular perturbation control strategy for regulating the longitudinal flight dynamics of an Unmanned Air Vehicle (UAV). The proposed control strategy is based on a four-time-scale (4TS) decomposition that includes the altitude, velocity, pitch, and flight path angle dynamics, with the control signals being the elevator deflection and the throttle position. The nonlinear control strategy drives the system to follow references in the aerodynamic velocity and the flight path angle. In addition, the control strategy permits to select the desired dynamics for all the singularly perturbed subsystems. Numerical results are included for a realistic nonlinear UAV model, including saturation of the control signals.