Flight control and flight experiments of a tilt-propeller VTOL UAV

The purpose of this work is to present a study on the stability and control of an unmanned, fixed wing, vertical take-off and landing aerial vehicle. This airplane is driven by a fixed-pitch tilt-propeller system with the capability of vertical take-off and landing as well as conventional flight. The novelty of the vehicle is the use of a fixed-pitch propeller system instead of variable-pitch tilt-rotors. There are three flight modes: vertical, transitional and conventional flight modes. Each flight mode has different dynamic characteristics. Therefore, these modes each need dedicated flight control methods. In this paper, the equations of motion are generated by modelling the aerodynamic and propulsion forces and moments. After performing trim condition calculations, longitudinal stability characteristics are investigated for each flight mode. The control methods are described for vertical, transitional and conventional flight modes. Stability augmentation systems, which consist of proportional and proportional/integral controller, are applied. A number of flight tests, including vertical, transitional and conventional flights, have been successfully performed with a prototype aircraft.