Control validation with software-in-the-loop for a fixed-wing vertical takeoff and landing unmanned aerial vehicle with multiple flight stages

Unmanned Aerial Vehicles (UAVs) are aircraft without a human aboard that can fly autonomously or be remotely piloted. Several configurations of UAVs have been developed to fulfill the requirements of different applications. Between them, it is possible to highlight the tailsitter, a hybrid design with the advantages of fixed-wing and Vertical TakeOff and Landing (VTOL) aircraft. A tailsitter UAV with simplicity as its main characteristic is AVALON (Autonomous VerticAL takeOff and laNding), which also has the disadvantage of a complex operation due to its multiple flight stages. To enable its autonomous procedure, AVALON requires a control system capable of stabilising the flight during its entire operation. Therefore, this paper reports the validation of control structures based on proportional-derivative controllers for AVALON's flight stages with software-in-the-loop experiments in the flight simulator X-Plane. The results show small errors for most of the flight stages, with the exception of landing. Despite of being able to land vertically, it still presented large errors and a yaw variation during this last stage.