Abstract
Hybrid electric distributed propulsion tilt-wing UAVs show unlimited application prospects due to their high propulsion efficiency and vertical take-off and landing capabilities. Aiming at the power requirements of distributed propulsion tilt-wing UAVs, this article presents an optimization design method for series hybrid electric propulsion systems suitable for this type of aircraft. Based on the flight conditions and constraints of various modes, the power demand models for distributed propulsion tilt-wing UAVs are established for vertical flight mode, transition mode, and forward flight mode. The hybrid electric power solving models of each component of the series hybrid electric system are established by analyzing the series hybrid power architecture and power transmission paths. The hybrid electric system weight model is mainly decomposed into the weight model of each component and the fuel consumption model. Based on power demand and energy demand, a mass model of components such as batteries, engines, generators, power management and distribution systems are established. Besides, the fuel consumption characteristic curve of the scaled engine is established using the Willans line formulation, and the fuel consumption calculation in the full flight profile is completed. The optimization of the series hybrid electric system of a 200kg-class distributed propulsion tilting wing UAV under two mission profiles of urban freight and mountain freight and the sensitivity of the optimized results to performance are presented. The results show that the proposed method can sensitively capture the significant influence of the adjustment of the mission profile and the changes in the performance requirements of each flight phase, and adapt to various application scenarios.
Highlights
Compared with the conventional fixed-wing unmanned aerial vehicle (UAV), vertical take-off and landing (VTOL) aircraft has lower energy efficiency and cruising speed, but can take off and land almost anywhere, showing unlimited application prospects [1]
These researches on hybrid electric propulsion system based on flight profile and power requirements of the conventional and distributed propulsion fixed-wing UAV have certain reference significance, but they cannot be directly extended to the design field of series hybrid electric system (S-HES) of distributed propulsion tilt-wing UAV
To compensate for the deficiency of the existing research, this paper presents a new optimization design method for the S-HES of the distributed propulsion tilt-wing UAV
Summary
Compared with the conventional fixed-wing unmanned aerial vehicle (UAV), vertical take-off and landing (VTOL) aircraft has lower energy efficiency and cruising speed, but can take off and land almost anywhere, showing unlimited application prospects [1]. Christopher [21] examined state-of-the-art hybrid-electric system modeling for aircraft design, and indicated that the existing power supply strategy of hybrid electric systems can be continuously optimized to achieve optimal performance throughout the mission These researches on hybrid electric propulsion system based on flight profile and power requirements of the conventional and distributed propulsion fixed-wing UAV have certain reference significance, but they cannot be directly extended to the design field of S-HES of distributed propulsion tilt-wing UAV. The method consists of a series of physical and mathematical models describing the characteristics of the series hybrid electric distributed propulsion tilt-wing UAV and a global optimization model based on the particle swarm algorithm with Cauchy mutation Using this method, the rapid conversion of the top-level design requirements of distributed propulsion tilt-wing UAV to the optimal power supply strategy, design power and mass distribution scheme of the S-HES can be completed in the early design stage.
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