Modeling and Control of a Novel Hybrid Coaxial and Tilt Rotor Aircraft

This paper presents a novel structural configuration of small-sized multi-rotor unmanned aerial vehicle (UAV). To enhance the endurance of multi-rotor UAV, large coaxial rotors are combined with four small tilt rotors. The large coaxial rotors provide vertical lift with high efficiency, while the small tilt rotors control attitude and provide omnidirectional thrust. First, a six-degree-of-freedom pose dynamics model is established for the proposed UAV. Secondly, a nonlinear controller is designed, and the stability of the position-attitude control system is rigorously proven. Furthermore, in response to the redundant characteristics of the actuators and the dynamic differences between two rotor systems, a lift-splitting control allocation algorithm is proposed. Finally, experiments and simulations are conducted to validate the performance of both the proposed UAV and control algorithm.