Promoting The Maneuverability and Fault-tolerance Capabilities of Dual-system VTOL UAVs

Abstract This paper proposes a new architecture for the flight control system of dual-system vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs). Having two separate systems for vertical and horizontal thrust in addition to the conventional control surfaces makes it the simplest VTOL UAV configuration, however, less employment of its controls redundancy is a drawback and a waste of its inherent capabilities. The main contribution of the designed control system is to employ the control's redundancy to enhance the airplane's maneuverability and to achieve fault-tolerance via the control allocation technique, thus benefiting from the vertical rotors during all the flight phases rather than having them as dead weights during the majority of the flight. The designed control system performs full flight missions including VTOL, transitions, cruise, and loiter in fault and fault-free cases with allowable commands for all the healthy controls according to their effectiveness, following the desired trajectory while minimizing the energy consumption and aerodynamic drag as well. A severe fault scenario is presented that includes sudden jamming of all the control surfaces where the control system successfully completed the intended mission as in the fault-free case. The proposed control system proved to enhance the maneuverability by achieving a 38% reduction in the coordinated steady-level turn radius at a given flight speed compared to the minimum turn radius achieved using the control surfaces only. The results reveal the dual-system configuration's safety and reliability features, recommending it as a first choice in VTOL UAVs applications.