Singular Perturbation Control for the Longitudinal and Lateral-Directional Flight Dynamics of a UAV

Abstract

This paper presents a singular perturbation control strategy for regulating both the longitudinal and the lateral-directional flight dynamics of an Unmanned Aerial Vehicle (UAV). The proposed control strategy is based on a double four-time-scale (4TS) decomposition of the longitudinal and lateral-directional dynamics. The longitudinal dynamics include the altitude, velocity, pitch, and flight path angle dynamics, with the control signals being the elevator deflection and the throttle position, while the lateral-directional dynamics include the side-slip angle, bank angle, yaw rate and roll rate dynamics, with the control signals being the aileron and rudder deflection. The nonlinear control strategy drives the system to follow references in the aerodynamic velocity, the flight path angle and the load factor, which in return provides references in bank angle, side-slip angle and yaw rate. In addition, the control strategy allows to select the desired dynamics for all the singularly perturbed subsystems. Numerical results are included for a realistic nonlinear UAV model, including control saturation and presenting control robustness capabilities under unmodelled dynamics.