The transition flight of tilt-propulsion UAV is a complex and time-varying process, which leads to great challenges in the design of a stable and robust controller. This work presents a unified model predictive controller, which can handle the full envelope from vertical take-off and landing to cruise flight, to mean that the UAV can achieve a near-optimal transition flight under uncertainty conditions. Firstly, the nonlinear dynamic model of the tilt-propulsion UAV is developed, in which the aerodynamic/propulsion coupling effect of the ducted propeller is considered. Then, a control framework, including global trajectory planning and finite horizon control, is designed. Taking the planned global trajectory as the reference input, a controller is proposed with an inner layer based on ILQR optimization and an outer layer based on feedback correction and forward rolling of the MPC frame. The ILQR-MPC controller has high computational efficiency to deal with nonlinear problems, and has the ability to give full play to UAV’s control ability and suppress uncertainty. Finally, the simulation results show that ILQR-MPC controller obviously performs better than the ILQR feedforward controller, and gains a scheduling PID controller and MPC controller.

Aiming at the vertical take-off and landing mode of tilt-propulsion UAV with uncertainties such as external environment disturbance and internal parameter perturbation, this paper studies the trajectory tracking control, and proposes an internal and external double loop sliding mode control scheme based on nonlinear extended state observer (NLESO). Firstly, according to the characteristics of tilt-propulsion UAV, the dynamic model of propulsion system, aerodynamic model of fuselage/wing and yaw rudder, and dynamic equation are established in turn to complete the dynamic modeling work. Then, the internal and external uncertainties are regarded as lumped disturbances, and NLESO is designed to estimate them and compensate the control system. Afterwards, based on NLESO and sliding mode control method, the position and attitude double loop controller of VTOL mode is designed. Finally, the Lyapunov function is designed to analyze the stability of NLESO and the whole control system. Simulation results show that the proposed method significantly improves the trajectory tracking response speed and the ability to suppress uncertainties of vertical take-off and landing mode of tilt dynamic UAV.