結合四軸飛行器和橢圓斜環翼的垂直起降無人飛行器之創新設計

Abstract

本研究提出一種結合四軸飛行器與橢圓斜環翼之混合式垂直起降無人飛行器設計，藉由將四軸螺旋槳整合於環形機翼內部，以降低巡航時外露葉片所造成的額外阻力，同時兼具多旋翼垂直起降能力與固定翼長航程巡航效率。研究中建立環形翼、箱形翼、類環形箱形翼、雙後掠翼、前掠翼加後掠翼及傳統單翼等多種翼型模型，從飛行穩定性、氣動效率、翼尖渦流及結構性能等面向進行比較。 研究結果顯示，各雙翼及封閉式翼型於原始設計下仍需透過升力分布調整方能滿足縱向靜穩定條件，但相關文獻指出，此類修正對氣動效率影響有限，因此後續分析仍以原始模型進行比較。在氣動性能方面，雙後掠翼具有最高升阻比，而環形翼則具有最低阻力係數，整體升阻比僅略低於雙後掠翼，展現良好的巡航效率。此外，環形翼因封閉式結構可有效抑制翼尖渦流生成，相較於開放式雙翼具有較少之渦流結構，並兼具降低誘導阻力之潛力。結構分析結果顯示，封閉式翼型之最大位移與最大應力均明顯低於開放式翼型，其中環形翼具有最低最大應力；即使於機翼內部開設螺旋槳安裝空間後，仍能維持較佳之結構剛性，顯示其適合作為整合四軸推進系統之機翼構型。 綜合各項分析結果，橢圓斜環翼兼具良好的氣動性能、結構優勢及整合四軸推進系統的潛力，可作為短翼展混合式VTOL 無人飛行器之新型機翼設計，並為未來原型製作、飛行驗證及最佳化設計提供重要參考。

This study proposes a novel hybrid Vertical Take-Off and Landing unmanned aerial vehicle (VTOL UAV) that integrates a quadcopter with an elliptical oblique ring wing. By embedding the four propellers within the ring wing, the proposed configuration reduces the additional drag caused by exposed rotor blades during cruise flight while retaining the vertical take-off and landing capability of multirotor UAVs and the high cruise efficiency of fixed-wing aircraft. Several wing configurations, including a ring wing, box wing, ring-like box wing, dual swept-back wing, forward-swept/rearward-swept wing, and conventional monoplane, were established and systematically investigated. The aerodynamic and structural performances of these wing configurations were evaluated and compared in terms of longitudinal stability, aerodynamic efficiency, wingtip vortex characteristics, and structural strength. The simulation results indicate that the original biplane and closed-wing configurations do not satisfy the requirements for longitudinal static stability and require modifications to the lift distribution between the front and rear wings. However, previous studies have shown that such modifications have only a limited influence on aerodynamic efficiency; therefore, the original wing models were adopted for the subsequent comparative analyses. Among the investigated configurations, the dual swept-back wing achieved the highest lift-to-drag ratio, whereas the ring wing exhibited the lowest drag coefficient. Although its lift-to-drag ratio was slightly lower than that of the dual sweptback wing, the ring wing demonstrated excellent cruise performance due to its reduced aerodynamic drag. Furthermore, the closed-loop geometry of the ring wing effectively suppressed the formation of wingtip vortices, resulting in fewer vortex structures than those observed in open-wing configurations and offering the potential to reduce induced drag. Structural analysis further revealed that closed-wing configurations exhibited significantly smaller maximum deformation and lower maximum stress than open-wing configurations. Among all the wing models, the ring wing produced the lowest maximum stress. Even after introducing openings within the wing to accommodate the propellers, the ring wing maintained superior structural stiffness, demonstrating its suitability for integrating a quadcopter propulsion system. Based on the comprehensive aerodynamic and structural evaluations, the proposed elliptical oblique ring wing provides an effective balance between aerodynamic performance, structural integrity, and propulsion-system integration. These characteristics make it a promising wing configuration for short-span hybrid VTOL UAVs and provide a valuable foundation for future prototype development, flight validation, and aerodynamic optimization.