Flight control system for small-size unmanned aerial vehicles: Design and software-in-the-loop validation

Currently there is a large interest in low cost unmanned aerial vehicles (UAV) development aimed to civilian applications. This paper describes the development and the software-in-the-loop validation of a flight control system for a small fixed wing UAV. The proposed approach follows standard tecniques for modeling, linearizing and decoupling the highly nonlinear six degrees-of-freedom dynamics of the vehicle. As a novelty in the UAV field, the participation factors analysis is applied in order to validate the decomposition into longitudinal and lateral-directional dynamics. Thus a linear quadratic regulator is developed for controlling the airspeed and the altitude, while a cascaded proportional-integral-derivative control is adopted for the heading tracking of the lateral dynamics, so to obtain the full waypoint navigation. In this work the lack of ailerons can be considered a peculiar feature of the considered platform since it determines a greater difficulty in controlling the flight of the UAV with respect to other airframe platforms.