Robust attitude control for tail-sitter unmanned aerial vehicles in flight mode transitions

Tail-sitter unmanned aerial vehicles (UAVs) can flight as rotorcrafts as well as fixed-wing aircrafts, but it is hard to control the flight mode transition. The vehicle dynamics involves serious parametric uncertainties, highly nonlinear dynamics, and is easy to be affected by external disturbances, especially during the mode transition. This paper presents a robust control method for a kind of tail-sitter UAVs to achieve the flight mode transition. The robust controller is proposed based on the state-feedback control scheme and the robust compensation method. The proposed control method does not need to switch the coordinate system, the controller structure, or the controller parameters during the mode transitions. Theoretical analysis is given to guarantee the robustness stability of the designed flight control system. Numerical simulation results are presented to show the advantages of the proposed control method compared with the state-feedback control method and the sliding mode control approach.