豆娘飛行動力最佳化分析與飛行操控機制研究

Optimal analysis of flight dynamics and investigation of flight control mechanism for damselfly

賴渝翔(Yu-Hsiang Lai)

指導教授 ： 楊鏡堂

國立臺灣大學/工學院/機械工程學研究所/博士(2021年)

https://doi.org/10.6342/NTU202101477

摘要

本研究解析豆娘最佳的飛行動力策略及揭露豆娘的飛行操控機制，對於仿昆蟲拍撲微飛行器的設計參考及飛行器的操控策略提供創新的見解。四翅昆蟲能做出許多高難度的飛行動作，如急轉、後飛及加速前飛等，吸引了科學家的興趣，並已用於微飛行器的設計應用上，其中豆娘由於變化的翅膀動作及較低的拍撲頻率在工程上更具有可實現性。
本研究透過拍攝真實豆娘飛行姿態以量化其飛行動作，採行三維暫態數值模擬方法及粒子影像測速法分析身體、翅膀形態及動作與流場的交互作用，以自推進模式計算豆娘飛行速度，以關聯性分析及最佳化分析方法釐清不同運動參數與氣動力性能之相關性及找出最佳運動參數組合，最後提出利用不同翅膀動作的飛行操控策略。
研究結果顯示在懸停時，豆娘(Matrona cyanoptera)的翅膀形態是屬於翼柄(petiolation)形狀，翼根渦漩(root vortex, RV)不易停留，翼前緣渦漩(leading-edge vortex, LEV)可穩定生成，豆娘可透過較大的拍撲振幅及較大的翅膀平移階段產生足夠的升力來懸停。反之，蜻蜓(Neurothemis ramburii)由於翼根較寬闊，翼根渦漩與脫離的翼前緣及翼後緣渦漩形成的干擾結構影響後翅翼前渦漩發展，蜻蜓是透過較快的拍翅頻率及較大的旋轉振幅，產生足夠的升力來懸停。
前飛時，受到身體形態的限制，短腹幽蟌(Euphaea formosa)的後翅拍動範圍位在身體下方且振幅較小，在前翅領先相位時，後翅不易受到前翅脫離尾流影響，因此可產生較佳的升推力。此外由於旋轉動作的差異，前翅脫離尾流方向的不同造成兩種豆娘(Matrona cyanoptera and Euphaea formosa)的最佳推力相位發生在不同翅膀相位。此外，前後翅交互作用對於後翅的影響較大，在不同翅膀相位間，後翅的氣動力差異較大，由於短腹幽蟌的後翅振幅較小，整體相位效應較不顯著，反之，白痣珈蟌後翅貢獻較大升推力，相位效應較明顯。本研究指出不同物種間並沒有所謂的最佳相位，昆蟲會依照其形態上的限制，選擇適當的翅膀相位來滿足其所欲達到的飛行模式。
在飛行策略方面，本研究開發四翅自推進模式探討相位效應顯著的白痣珈蟌在不同翅膀相位時對飛行速度的效應，提出利用相位調節的飛行操控策略。結果顯示同相位有較大垂直速度，卻也伴隨著較大的速度振盪，通常會用在起飛或加速階段。而反相位在速度的振盪最小，這意味著平穩地飛行，因此推測昆蟲在長距離巡航時會採用此相位模式，後翅領先相位通常有較快垂直速度，前翅領先相位有較快前飛速度，但隨著相位離反相位越遠，速度振盪越大，平穩飛行的表現越差。
對於相位效應較弱的短腹幽蟌，本研究選擇了豆娘及蜻蜓主要的動作差異當成研究參數—拍撲平面傾斜角、翅膀旋轉時間及翅膀相位，探討後翅變化的動作對水平速度效率的影響。研究發現拍撲平面傾斜角度對於水平速度效率有最大影響，其次是旋轉時間，相位差則影響不大。最佳水平速度效率則是發生在高傾斜角與小旋轉時間的結合，這個組合與短腹幽蟌原始動作相比，可以提升22%水平速度效率。除了相位操控策略外，以拍撲平面傾斜角結合旋轉時間也是可利用的操控策略，一個大的傾斜角搭配一個小的旋轉時間有最佳的水平速度效率，適合用於長時間巡航飛行。一個小的傾斜角結合大的旋轉時間適合用在懸停飛行。

關鍵字

豆娘 ； 相位差 ； 旋轉時間 ； 拍撲平面傾斜角 ； 推力效率 ； 水平速度效率 ； 前後翅交互作用

並列摘要

The purpose of the dissertation is to analyze the optimal flight dynamics and reveal the flight control mechanism for damselflies, which can provide new insights into the design and flight control strategy of insect-like flapping micro aerial vehicles. Four-wing insects can achieve many difficult flight motions, such as sharp turns, backward flying, and accelerated forward flying, which have attracted the interest of scientists and have been used in the design and application of micro aerial vehicles. Among them, varied wing motions and lower flapping frequency of damselfly is more achievable in engineering.
We photographed the flying damselflies to characterize the flight motions. Three-dimensional transient numerical simulation and particle image velocimetry were used to analyze the interaction between the body, wing morphology and motion, and the flow field. The self-propulsion model was used to calculate the flight velocity of damselflies. Correlation analysis and optimal analysis were used to clarify the correlation between varied wing kinematics and aerodynamic performance and investigate the best combination of varied wing kinematics. Finally, this research proposed a flight control strategy using varied wingkinematics.
The results indicated that in hovering, the wake of a damselfly sheds smoothly because of slender petiolation; a vertical force is generated steadily during the stage of wing translation. Damselflies hover with a longer translational phase and a larger flapping amplitude. In contrast, the root vortex of a dragonfly impedes the shedding of wake vortices in the upstroke, which results in the loss of a vertical force; the dragonfly hence hovers with a large amplitude of wing rotation and a larger flpping frequency.
In forward flying, restricted by the body morphology of Euphaea formosa, the flapping range of the hindwing is below the body. With the forewing in the lead, the hindwing is farther from the forewing, which is not susceptible to the wake of the forewing, and enables superior lift and thrust. Because of the varied rotational motions, the different shed direction of the wakes of the forewings causes the optimal thrust to occur in different wing phases. The vertical and horizontal forces of the hindwings of the two damselflies differ greatly between various phases. Because of the smaller flapping amplitude of the hindwing of E. formosa, the hindwing contributes a smaller force than that of the forewing; the overall difference between the different phases is hence less significant. In contrast, the hindwing of Matrona cyanoptera contributes a larger force than that of the forewing; the effect of wing-wing interaction is more obvious. Moreover, regarding the wing-wing interaction on the aerodynamic efficiency, our results show that the wing-wing interaction is a compromise: when a specific phase has a greater lift efficiency, it is generally accompanied by poor thrust efficiency, and vice versa. Because of its biological limitations, a damselfly can use an appropriate phase to fulfill the desired flight mode.
In terms of flight strategy, we used M. cyanoptera as an object, to which wing-wing interaction is more obvious. We developed the four-wing self-propulsion model to calculate the flight velocity of damselfly and explore the effect of wing phase on the flight velocity. We found that, although motion in phase has a large vertical velocity, which is typically applied in a take-off or acceleration phase, it is also accompanied by a large oscillation of the velocity. An out-of-phase motion has the smallest oscillation of velocity, which implies smooth flying, so we speculate that insects would use this wing phase when cruising large distances. In addition, this work indicates that the forewing in the lead phase has generally a greater horizontal velocity; the hindwing in the lead phase has a greater vertical velocity. When the wing phase is further from the case out of phase, the greater is the oscillation of the velocity, the less smooth the flying becomes. In the efficiency part, varied wing phases have similar power consumption, which implies that a damselfly could have an effective flight maneuverability via phase modulation.
Reffering to E. formosa, to which wing-wing interaction is insignificant, we reveal the hindwing kinematics of the damselfly that are optimal for the horizontal efficiency, which is a major concern of a bio-inspired micro-aerial vehicle. The wing kinematics of the hindwing have a significant impact on the horizontal efficiency, in which the forewing-hindwing interaction affects the vortex of the hindwing. The parameters of the hindwing kinematics were extracted from the difference in wing kinematics between a dragonfly and a damselfly: stroke-plane angle, rotation duration and wing phase. The results show that the optimal wing kinematics of the hindwing occur at a large stroke-plane angle and a small rotation duration, in which the horizontal efficiency might increase up to 22% compared with the original motion of the hindwing. The stroke-plane angle is highly positively correlated with thrust efficiency, whereas the rotation duration is moderately negatively correlated; the wing phase has the least correlation. In a flight strategy for a micro-aerial vehicle, a large stroke-plane angle combined with a small rotation duration yields an optimal horizontal efficiency, which is suitable for a flight of long duration. A small stroke-plane angle combined with a large rotation is suitable for hovering flight because it leads to a large negative horizontal force and small vertical force.

並列關鍵字

damselfly ； wing phase ； rotation duration ； stroke plane angle ； thrust efficiency ； horizontal efficiency ； forewing-hindwing interaction

參考文獻

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