A vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV) can meet both VTOL and horizontal flight performance, but how to achieve a safe and stable transition is a research focus of this type of aircraft. According to the overall configuration characteristics of VTOL UAV, aerodynamic models of lift fan, lift duct and induced wing surface of VTOL UAV were established. Three flight modes of induced VTOL UAV are studied, including hover, transition and horizontal flight. The method of longitudinal flight balance of UAV in transition mode is also studied. Finally, a UAV is taken as an example to conduct the research of transition flight mode balancing and flight simulation with the method presented in this paper. The results show that the proposed method can reasonably give the control quantity and longitudinal attitude of UAV in the whole transition mode, so that the UAV can achieve a steady transition flight.

An accurate description of the transition corridor is of great significance for the flight process of the vertical take-off and landing (VTOL) fixed-wing unmanned aerial vehicle (UAV). To study the transition flight process of vertical take-off and landing fixed-wing UAVs, the dynamic model and transition corridor model of this type of UAV are established in the current article. The method for establishing the model is based on a reasonable match of the power and aerodynamic force of this type of UAV. From the perspective of flight dynamics, the ducted lift-increasing system’s deflection angle–speed envelope is studied with the maximum lift coefficient of the wing and the system’s available power. The influence of the overall parameters and energy parameters of the UAV on the deflection angle–speed envelope of the ducted lift-increasing system is analyzed, and a method is proposed to expand the vertical take-off and landing fixed-wing UAV’s transition corridor. Taking the UAV as the object, using the established model, the transition flight corridor of the UAV is obtained, the influence of the control parameters on the transition flight is studied, and the appropriate transition flight control strategy is determined. At the same time, the influence of the overall parameters and energy parameters on the transition corridor is calculated. According to the calculation results, the effect of expanding the flight corridor of the UAV is more obvious when increasing the available power than when increasing the aerodynamic parameters by the same proportion.

The longitudinal flight stability of the ducted vertical take-off and landing fixed-wing UAV during the flight state of hovering and transition is studied. Firstly, based on the Blade-Element Momentum Theory (BEMT) and experimental data, a coaxial dual-rotor ducted aerodynamic model and a thrust ducted aerodynamic model based on characteristic cross-section calculations are established. The model parameters are identified according to the experimental data. Secondly, a UAV flight dynamics model with thrust duct deflection is established according to the six-degree-of-freedom equations. Finally, the case UAV was used to solve the longitudinal balance and stability analysis of hovering and transition state with the established model method, and compared with the hovering experimental results. The results show that the UAV flight dynamics model combined with the ducted dynamic model established in the article can accurately describe the longitudinal flight stability characteristics of this type of aircraft.

Aiming at the problem of energy collection and consumption of solar-powered UAV under different maneuvers, an energy collection model combining solar-powered UAV attitude and solar radiation was established. Firstly, the ASHRAE model was used as the solar radiation estimation model in the flight environment. Secondly, the energy harvesting model of the solar-powered UAV is deduced by the relationship between the attitude of the UAV, the relative position of the sun and the earth. The experimental data was used to establish the energy consumption model of solar-powered UAV in different flight states. Finally, the flight time of the same mission path under different operating modes is obtained through simulation. Simulation results show that when the solar-powered UAV is hovering at a height of 3 000 meters and a radius of 50 meters, the flight time of aileron operation is 7.19% longer than power differential operation; when hovering at a radius of 170 meters, the flight time of the two operations is almost equal; when hovering at a radius of 600 meters and flying in a line, the flight time of the power differential operation is about 1.08% longer than that of the aileron operation.