Trajectory tracking for a Non-Conventional UAV

The aim of the present paper is the design of a flight control system for a Tandem – Canard UAV, useful in the whole flight envelope, both Out of Ground Effect (OGE) and In Ground Effect (IGE) conditions. Because of the particular arrangement of the studied aircraft, a general mathematical model has been built in order to obtain non-linear analytical equations for longitudinal aerodynamic coefficients both in OGE and in IGE flight. So the dynamic behaviour of the UAV may be studied during every flight phases i.e. in the whole range of altitude. To consider the strong variation of aerodynamic parameters due to the ground effect presence, a robust control technique (LQG/LTR) has been used to design the control system. Because Phugoid mode is strongly affected by ground effect, a Stability Augmentation System has been implemented in order to increase Phugoid damping. The controller has shown suitability to track both out of ground effect and in ground effect trajectories. Besides, it possesses robustness properties either in presence of wind disturbances.