Sail Tracking Control for Hybrid Aquatic UAV

The aquatic UAV is a kind of unmanned system capable of operating in air and on the water surface. To overcome the problem caused by different media, designing a hybrid mechanism that can adapt its morphology for flying and sailing is necessary. In addition, an efficient sail and rudder control system is essential because locomotion on the water surface is performed using only wind kinetic energy. In this study, we simulated the sailing of a solar-powered hybrid aquatic UAV under fixed wind conditions. First, the operating environment and system modeling for wind, wing-sail, and rudder force for water surface locomotion were implemented. In addition, a no-go zone was derived by running a velocity prediction program to confirm the sailing performance of the designed UAV. Then, low-level wing-sail controller and a fuzzy interface system based rudder controller were designed to control the behavior of the 3-DOF dynamic model. An objective function was applied in the low-level wing-sail controller to derive the wind direction needed to produce the maximum thrust, and fifteen fuzzy rules were used in the rudder controller by defining a membership function for heading angle and rotational speed. Finally, the feasibility of the control system in downwind and upwind scenarios was verified by the waypoint tracking simulation based on the nonlinear guidance logic.