Hybrid power systems are now widely utilized in a variety of vehicle platforms due to their efficacy in reducing pollution and enhancing energy utilization efficiency. Nevertheless, the existing vehicle hybrid systems are of a considerable size and weight, rendering them unsuitable for integration into 25 kg compound-wing UAVs. This study presents a design solution for a compound-wing vertical takeoff and landing unmanned aerial vehicle (VTOL) equipped with an improved series hybrid power system. The system comprises a 48 V lithium polymer battery(Li-Po battery), a 60cc internal combustion engine (ICE), a converter, and a dedicated permanent magnet synchronous machine (PMSM) with four motors, which collectively facilitate dual-directional energy flow. The four motors serve as a load and lift assembly, providing the requisite lift during the take-off, landing, and hovering phases, and in the event of the ICE thrust insufficiency, as well as forward thrust during the level cruise phase by mounting the variable pitch propeller directly on the ICE. The entire hybrid power system of the UAV undergoes numerical modeling and experimental simulation to validate the feasibility of the complete hybrid power configuration. The validation is achieved by comparing and analyzing the results of the numerical simulations with ground tests. Moreover, the effectiveness of this hybrid power system is validated through the successful completion of flight test experiments. The hybrid power system has been demonstrated to significantly enhance the endurance of vertical flight for a compound-wing VTOL by more than 25 min, thereby establishing a solid foundation for future compound-wing VTOLs to enable multi-destination flights and multiple takeoffs and landings.

For a longer endurance of vertical and level cruise flight, an electro-gasoline hybrid power system is introduced on a compound-wing unmanned aerial vehicle (UAV). After discharging during vertical flight, the battery pack is charged by a piston engine-driven generator, which simultaneously powers the UAV for level cruise flight. A charging model is established based on the configuration of the hybrid power system. Considering fuel consumption and battery attenuation within the typical flight profile of a compound-wing UAV, an optimized charging plan is developed using dynamic programming to determine the trajectory of the generated power sequence. To address deviations between ideal and practical flight conditions in terms of charging performance, a feedforward compensation is introduced to improve optimal tracking control within the dynamic programming framework. Simulations validate the effectiveness of the optimized charging plan, while testbench experiments confirm improvements achieved through compensation enhancement. The results demonstrate practicality with minimal overall cost compared to other conventional control plans.

This paper proposes a power architecture for a Compound-Wing Unmanned VTOL to supply power during the hovering state. To enhance the hovering efficiency of the UAV while considering the cruising efficiency, the layout structure of a traditional Compound-Wing Unmanned VTOL is optimized. A high-power-density hybrid-power range-extender using an ICE (internal combustion engine) suitable for the Compound-Wing Unmanned VTOL is designed. The engine electronic control unit (ECU) suitable for the range-extender is presented by using a locally linearized state-space equation and LQR (Linear-Quadratic Regulator). Simulation experiments, ground running tests, and flight tests have been conducted to verify the performance of the Compound-Wing Unmanned VTOL and its power architecture.

The multirotor configuration unmanned aerial vehicle faces a significant challenge in simultaneously achieving long-range operation and high payload capacity. This paper investigates the power management strategy for a novel fuel–electric hybrid aircraft that incorporates lifting wings to reduce rotor load and a range-extend system to enhance energy supply. An equivalent consumption minimization strategy is developed to optimize, in real time, the power distribution between the internal combustion engine and the battery. The primary innovation of this paper lies in the application and rigorous validation of the equivalent consumption minimization strategy on this new aircraft configuration, which effectively minimizes total energy cost by optimally balancing fuel consumption and battery degradation, resulting in significantly reduced fuel usage and a more stable power output compared to conventional approaches.

A composite strategy is proposed to address the optimal power management for a hybrid powered compound-wing aircraft, which integrates bang–bang regulation with optimal demand chasing regulation. The electro-gasoline hybrid power system enhances the overall flight endurance of vertical take-off and landing compound-wing aircraft. The power consumption in level flight appears to be much lower than that in hovering, enabling the hybrid power system to simultaneously energize and charge the battery pack. In order to minimize fuel consumption and battery pack degradation during level cruise flight, a power management strategy that serves for both battery charging and thrust energizing is worthy of careful consideration. To obtain the desired features and design the regularity strategy of the power system, linear and nonlinear models are established based on the configuration of an electro-gasoline series hybrid power system installed in the proposed aircraft, with mathematical modelling of key components and units. A notable feature of semi-fixing for battery voltage and engine rotational speed has been qualitatively identified and subsequently quantitatively validated on the testbench. After conducting simulations and comparing with other strategies, the composite strategy demonstrates appropriate fuel consumption and battery degradation, effectively achieving cost minimization. Testbench evaluation confirms the effectiveness of this proposed power management strategy. Furthermore, the practicality of the hybrid power system and its associated level flight composite power management strategy are validated by tests conducted on a 30 kg aircraft prototype, thereby showcasing the potential to enhance flight performance.

Multi-rotor UAVs suffer from a sharp decline in rotor efficiency during high-speed cruise, severely limiting their endurance. To address this issue, this paper proposes a vertical takeoff and landing configuration that integrates a lift wing with an independent tail-mounted pusher. The wing lift unloads the vertical rotor load, while the pusher thrust offsets part of the horizontal drag, thereby enabling both vertical takeoff and landing and efficient cruise. A longitudinal trim model is established to theoretically compare the thrust and power characteristics of three configurations. A modular validation platform capable of switching among three propulsion configurations is built, and an independent closed-loop pusher-thrust controller is implemented on an auxiliary computer without modifying the flight controller firmware. Comparative flight experiments are conducted along the same route under equal total mass conditions. The results show that the energy consumption per unit distance during cruise of the complete configuration is reduced by approximately 58% compared with the pure multi-rotor. Compared with the wing-only configuration without tail propulsion, the cruise speed is increased by approximately 27%, while the energy consumption per unit distance is reduced by approximately 19% at their respective natural cruise speeds. Speed fluctuations and attitude disturbances remain within acceptable ranges. By increasing the pusher thrust, the cruise speed can be extended to 25 m/s, breaking through the speed bottleneck of the no-tail-propulsion configuration; this upper limit is constrained by the thrust capability of the current tail-mounted pusher and propeller. These findings confirm the effectiveness of the synergistic mechanism of lift-unloading and thrust-sharing, demonstrate that independent pusher-thrust control is the key technology for achieving this performance advantage, and provide an experimental basis and an engineering solution for the design of lightweight, high-efficiency VTOL UAVs.