雀類在低雷諾數的飛行條件下，相比於現今同等尺度的小型無人機，具有更好的穩定性及靈活性適應複雜的環境，故本研究將以多自由度機構模擬綠繡眼前飛狀態下的飛行動作。該機構可分別控制拍撲角、折曲角及手部掃掠角，藉由單純拍撲運動疊加不同關節動作，設計出六種動作模式，另外針對翼尖四根主要飛羽，設計四組不同開衩深度的羽毛。透過荷重元於風洞及真空艙內量測升阻力及慣性力，藉此了解不同關節動作對拍撲飛行所產生的氣動力機制與翼尖開衩所帶來的效益。實驗結果顯示收折翼形態與折曲動作相較於展開翼拍撲，皆能有效使整個週期的升阻力波動降低進而維持更多升力減少阻力。前者平均升力增加原來的17%，平均阻力減少13%，在僅有單自由度拍撲動作的飛行器設計上，展弦比控制在4以下會有較佳的飛行效率；後者平均升力能增加80%，平均阻力減少7%，如需有較大的負載能力，可在上拍過程中增加折曲動作來提供更多的升力，不過此時的展弦比不宜低於4以下來避免反效果。手部掃掠動作會增加下拍時的推力，能大幅減少56%的平均阻力，不過平均升力也會減少13%，如考量到較快的加速性能，可適當增加翅膀外翼掃掠動作，提供更多推力，但負載能力也會有所下降。最為接近綠繡眼完整動作的模式六，能在下拍後期產生較大翼尖速度局部加強渦流結構，平均升力增幅可達到143%，平均阻力則小幅增加6%，擁有最佳的升阻比表現，然而對於設計飛行器來說，在結構材料的選用與控制系統的設計上，會面臨極大的考驗。適當的翼尖羽毛開衩能增加較多升力及部分阻力，E=0.34能在滑行時提供最佳的升阻比，但在複雜的拍撲運動中，顯然較小的翼尖開衩羽毛有較理想的表現。透過本研究的發現，期望在未來能提供仿生拍撲飛行器設計之參考。

Under low Reynolds number flight conditions, passerines have better stability and maneuverability to adapt to complex environments than today's MAVs. Therefore, this study will use a multi-degree-of-freedom mechanism to simulate the forward flight of Zosterops japonica. The mechanism can control the flapping angle, folding angle and hand-sweeping angle respectively. By superimposing different joint motions on the simple flapping motion, six action modes are designed. In addition, four sets of primary feathers with different slot depths are designed to change the shape of wingtip morphology. The lift, drag and inertial force are measured in the wind tunnel and vacuum chamber through the load cell, to understand the aerodynamic effects of wingtip slots and different joint motions on flapping flight. The experimental results show that the swept wing shape and the folding motion can effectively reduce the lift and drag fluctuation throughout the cycle. Thereby maintaining more lift and reducing drag compared with the only flapping motion. In the design of MAVs with only single-degree-of-freedom flapping motion, an aspect ratio below 4 may have better flight efficiency. If MAVs need a larger load capacity, increasing the folding motion during the upstroke can provide more lift. At this time, the aspect ratio should not be lower than 4 to avoid adverse effects. Considering the faster acceleration performance, the sweeping motion of the outer wing can be appropriately increased to provide more thrust, but the load capacity will also be reduced. The complete motion of passerines has the best lift-to-drag ratio among all modes because a large wingtip speed strengthens the vortex. However, for the design of MAVs, the structural materials and the control system will be a big challenge. Appropriate wingtip slots can increase lift and drag. E=0.34 can provide the best lift-to-drag ratio while gliding, but obviously smaller wingtip slots have better performance in complex flapping modes. The findings of this study, it is expected to provide a reference for the design of bionic flapping aircraft in the future.

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