扑翼飞行器气动力测量技术研究进展与展望

扑翼飞行器是一种仿照鸟类飞行的新概念小型无人飞行器,区别于传统固定翼和旋翼飞行器,它主要通过机翼扑动与空气相互作用来提供飞行动力,从而实现飞行器的姿态变动。扑翼飞行器气动特性测试的实质是揭示在非定常流场环境下,扑翼飞行器气动力的产生机制,以及相关扑翼飞行器设计参数对气动特性的影响。通过气动试验方法为扑翼飞行器飞行控制和结构优化等研制工作提供数据支持,将对新型扑翼飞行器理论研究以及飞控品质的提升起到巨大的推动作用。     

一种超低空飞行的仿生扑翼飞行器的设计及分析

为研制既具备一定的负载能力,又具有高隐蔽性的飞行器,依据鸟类的飞行方式,设计了一种可以超低空飞行的仿生扑翼飞行器。首先,计算了扑翼飞行器传动机构的自由度,从原理上确定了设计方案的可行性,并确定了飞行器各个构件的尺寸;其次,利用设计软件Creo绘制飞行器三维模型,通过运动仿真得出飞行器的扑动符合设计要求;然后,利用ADAMS （automatic dynamic analysis of mechanical system,机械系统动力学自动分析）软件对飞行器进行动力学仿真,得到飞行器在扑动过程中的扑动幅度和角速度变化情况,验证了飞行器三维模型设计的合理性,并计算了飞行器旋转关节处的平衡力矩;最后,制作了扑翼飞行器的样机,并进行了室内和户外飞行试验。动力学仿真分析和飞行试验表明,所设计的扑翼飞行器扑动稳定性良好,具有较强的飞行能力和仿生隐蔽性,飞行效果达到预期。该扑翼飞行器可以进行超低空飞行,应用前景较广。     

仿生扑翼飞行器的气动效率研究

该文主要采用BLU-SGS混合动态网格隐式算法进行时间推进,空间离散采用二阶迎风格式的有限体积法。求解非定常Navier-Stokes方程,完成了二维不可压缩流场的数值模拟。在该基础上,通过积分计算的形式得到整个机翼平面的气动力,研究揭示了不同扑动频率、风速参数、减缩频率、雷诺数与飞行气动效率的关系,表明参数的合理调试对仿生扑翼飞行器的有效飞行起到重要影响。针对不同参数条件,研究分析了气动力以及气动效率结果,为后续气动特性问题的研究提供参考。     

扑动轨迹对扑翼气动特性影响的数值研究

国内外对扑翼飞行的气动性能进行了大量研究,这些研究大多针对特定运动轨迹下的扑翼,然而大量观察发现,昆虫在飞行时其翅膀会出现各种不同的运动形式,这些不同的翅膀运动方式必定对其气动性能产生重要影响。该文基于对昆虫的实验和数值模拟中常用的几种扑动轨迹模型分析,建立了三种具有相同准稳态气动力的扑翼扑动轨迹,并采用数值求解N-S 方程的方法,研究了前飞状态下不同扑动轨迹对扑翼气动特性产生的影响。结果显示扑动和转动均为简谐函数轨迹形式的扑翼具有较高的升举效率和推进效率。进一步通过对不同扑动轨迹扑翼流场分析得出,扑动轨迹不能改变扑翼产生的尾流性质,但可以影响涡的强度,从而使扑翼产生不同的气动性能。     

仿生扑翼模态分析研究与优化设计

微型扑翼飞行器是微型飞行器和扑翼飞行器的结合,是飞行器设计领域的研究热点,但在低雷诺数下存在升力不足的现象。已有研究表明,扑翼的弯扭耦合对于提高升力有效,弯扭耦合可通过共振激励放大驱动机理来实现,但该机理对扑翼的模态提出要求。本文首先建立仿生扑翼有限元模型,对其进行模态分析,并提出1种适用于扑翼的模态种类判别方法。为满足模态要求,提出了2种改进方案,并进行了有限元仿真验证。结合两种改进方案,提出双斜梁-主梁变截面扑翼模型。基于PCL语言对该模型进行参数化建模,采用遗传算法对其进行尺寸优化,得到满足模态要求的相对理想的仿生扑翼,为仿生扑翼的设计和优化提供重要的科学依据和工程应用价值。     

基于Unity3D的扑翼飞行器自主寻路的设计与实现

随着虚拟现实的飞速发展,Unity3D引擎成为此项技术的主要平台,相较传统仿真软件,存在高可视化的优势,其在工业仿真领域的应用逐步深入.基于U nity3D引擎对扑翼飞行器的自主寻路进行仿真设计,在U nity3D中导入扑翼飞行器,然后设计搭建寻路场景,通过NavM esh系统的应用和编写的脚本,实现扑翼飞行器的自主寻路.     

超音速飞行器翼—身组合体的颤振研究

飞行器的颤振是结构在高速气流中发生的一种自激振动现象,而这种现象在超音速和高超音速飞行器上极易发生。由于飞行器自身结构的复杂性,传统的组合体结构颤振分析在这种工况下会产生较大误差。利用特别适合复杂结构建模的动态子结构方法,针对飞行器在超音速飞行状态下高超音速流与飞行器自身结构的特点,考虑机翼、机身组合布局在颤振形态上产生的复杂情况,利用动态子结构中自由界面模态综合法,将整个飞行器分成机身、机翼子结构,基于非线性气动理论结合有限元计算软件,计算气动力分布情况并建立飞行器翼—身组合体系统的振动微分方程,对其进行颤振特性分析,得到飞行器在所设工况下的振动与颤振特性与颤振临界状态,实现全机气动弹性问题的仿真计算。为动态子结构方法应用于超音速飞行器的颤振研究提供理论基础,拓展了超音速飞行器组合体颤振的计算方法。     

基于Unity3D引擎的扑翼机构运动仿真

鉴于Unity3D引擎目前已成为虚拟现实技术研究使用的主流平台,在许多领域具有较好的开发前景,为了在可兼容虚拟现实和具有高可视化水平的Unity3D引擎中实现机械结构的有效运动,基于Unity3D引擎对扑翼式飞行器的扑翼机构进行了仿真设计.通过对扑翼机构的三级直齿圆柱齿轮减速器(作为传动机构)和空间曲柄摇杆机构(作为驱动机构)的运动学建模和仿真,在Unity3D引擎中导入扑翼式飞行器的模型,借助Unity3D引擎的高度可视化技术展现了飞行器扑翼机构的运动情况.实验证明,Unity3D引擎能够通过设计算法进行机械结构的运动模拟.     

扑翼式飞行器的发展与展望

本文简要介绍了扑翼式飞行器的国内外发展史,以及扑翼式飞行器相比于其他飞行器的优势,概述了当前扑翼式飞行器在国内外研究现状。以此为基础,讨论了现阶段扑翼式飞行器研究的关键技术,并对我国未来扑翼式飞行器的发展方向进行了展望。     

连翼布局飞行器飞行载荷与颤振分析

对相同总体设计条件下的传统布局飞行器的机翼和连翼布局飞行器的机翼进行了静气动弹性特性和颤振特性的对比分析。重点开展了考虑弹性变形的情况下,两种机翼在提供相同升力的条件下,结构所承受的气动载荷的对比分析及气动导数随动压变化趋势的对比分析。分析结果表明:与传统布局机翼相比,连翼布局机翼具有更高的设计灵活性;在相同的结构重量条件下,连翼布局机翼较之传统布局弯曲和扭转刚度特性更好,并具有较高的颤振速度;弹性情况下连翼布局机翼升力线斜率随动压增大而增大,且这种增加梯度受到后翼弯曲刚度的影响。     

Aerodynamic effects of flexibility in flapping wings

Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re ≈ 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small robotic insects and, to a limited extent, in understanding the aerodynamics of flapping insect wings.     

Dipteran wing motor-inspired flapping flight versatility and effectiveness enhancement

Insects are a prime source of inspiration towards the development of small-scale, engineered, flapping wing flight systems. To help interpret the possible energy transformation strategies observed in Diptera as inspiration for mechanical flapping flight systems, we revisit the perspective of the dipteran wing motor as a bistable click mechanism and take a new, and more flexible, outlook to the architectural composition previously considered. Using a representative structural model alongside biological insights and cues from nonlinear dynamics, our analyses and experimental results reveal that a flight mechanism able to adjust motor axial support stiffness and compression characteristics may dramatically modulate the amplitude range and type of wing stroke dynamics achievable. This corresponds to significantly more versatile aerodynamic force generation without otherwise changing flapping frequency or driving force amplitude. Whether monostable or bistable, the axial stiffness is key to enhance compressed motor load bearing ability and aerodynamic efficiency, particularly compared with uncompressed linear motors. These findings provide new foundation to guide future development of bioinspired, flapping wing mechanisms for micro air vehicle applications, and may be used to provide insight to the dipteran muscle-to-wing interface.     

柔性扑翼气动性能的数值研究

国内外对扑翼飞行的气动特性进行了大量研究,这些研究大多基于简谐扑动的刚性翼,然而大量观察发现鸟或昆虫飞行时,翅膀存在明显的柔性变形,这种变形对其气动性能具有显著的影响。该文针对一简化的二维柔性扑翼模型,采用数值求解N-S方程并耦合扑翼柔性变形方程的计算方法,研究了扑翼柔性变形对其气动性能的影响。结果显示扑翼的柔性变形改变了扑翼周围的涡结构,从而影响扑翼的气动性能;适当的柔性变形能延迟前缘涡的脱落,从而有效地改善扑翼的推进效率,但同时减弱了扑翼在低雷诺数环境中产生高升力的尾迹捕捉机制。     

Ionic Polymer Metal Composite Flapping Actuator Mimicking Dragonflies

In this study, variational principle is used for dynamic modeling of an Ionic Polymer Metal Composite (IPMC) flapping wing. The IPMC is an Electro-active Polymer (EAP) which is emerging as a useful smart material for `artificial muscle' applications. Dynamic characteristics of IPMC flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. A comparative study of the performances of three IPMC flapping wings is conducted. Among the three species, it is found that thrust force produced by the IPMC flapping wing of the same size as Anax Parthenope Julius wing is maximum. Lift force produced by the IPMC wing of the same size as Sympetrum Frequens wing is maximum and the wing is suitable for low speed flight. The numerical results in this paper show that dragonfly inspired IPMC flapping wings are a viable contender for insect scale flapping wing micro air vehicles.     

Wing‐kinematics measurement and flight modelling of the bamboo weevil C. buqueti

Insects are one of the most agile flyers in nature, and studying the kinematics of their wings can provide important data for the design of insect‐like wing‐flapping micro aerial vehicles. This study integrates high‐speed photogrammetry and three‐dimensional (3D) force measurement system to explore the kinematics of Cyrtotrachelus buqueti during the wing‐flapping flight. The tracking point at the wing tip of the hind wing was recorded using high‐speed videography. The lift‐thrust force characteristic of wing‐flapping motion was obtained by the 3D force sensor. Quantitative measurements of wing kinematics show that the wing‐flapping pattern of the hind wing of C. buqueti was revealed as a double figure‐eight trajectory. The kinematic modelling of the wing‐flapping pattern was then established by converting the flapping motion into rotational motion about the pivoting wing base in the reference coordinate system. Moreover, the lift force generated by C. buqueti during the wing‐flapping flight is sufficient to support its body weight without the need to use thrust force to compensate for the lack of lift force.Inspec keywords: video recording, force sensors, photogrammetry, kinematics, force measurement, aerospace componentsOther keywords: kinematic modelling, pivoting wing base, wing‐flapping flight, insect‐like wing‐flapping microaerial vehicles, high‐speed videography, 3D force sensor, Cyrtotrachelus buqueti, wing kinematics measurement, wing‐flapping motion pattern, lift‐thrust force characteristics, bamboo weevil C. buqueti, high‐speed photogrammetry, three‐dimensional force measurement system, 3D force measurement system, double figure‐eight trajectory     

State-space aerodynamic model reveals high force control authority and predictability in flapping flight

Flying animals resort to fast, large-degree-of-freedom motion of flapping wings, a key feature that distinguishes them from rotary or fixed-winged robotic fliers with limited motion of aerodynamic surfaces. However, flapping-wing aerodynamics are characterized by highly unsteady and three-dimensional flows difficult to model or control, and accurate aerodynamic force predictions often rely on expensive computational or experimental methods. Here, we developed a computationally efficient and data-driven state-space model to dynamically map wing kinematics to aerodynamic forces/moments. This model was trained and tested with a total of 548 different flapping-wing motions and surpassed the accuracy and generality of the existing quasi-steady models. This model used 12 states to capture the unsteady and nonlinear fluid effects pertinent to force generation without explicit information of fluid flows. We also provided a comprehensive assessment of the control authority of key wing kinematic variables and found that instantaneous aerodynamic forces/moments were largely predictable by the wing motion history within a half-stroke cycle. Furthermore, the angle of attack, normal acceleration and pitching motion had the strongest effects on the aerodynamic force/moment generation. Our results show that flapping flight inherently offers high force control authority and predictability, which can be key to developing agile and stable aerial fliers.     

扑翼空气动力学研究进展与应用

昆虫、鸟类与蝙蝠等生物具有高超的飞行能力,是扑翼飞行器的主要模仿对象。近年来,扑翼空气动力学领域的研究取得了很大进展,该文主要对其主要研究成果进行综述,重点介绍扑翼空气动力学各研究方向的最新进展,包括昆虫、鸟类与蝙蝠扑翼的主要升力机制,翅膀形态学参数与微观结构、翅膀柔性与动态变形、翼-翼干扰、翼-身干扰、个体间干扰及地面效应等对扑翼气动特性的影响。同时还对仿生扑翼飞行器气动研究的新进展进行了介绍,并提出了扑翼空气动力学所面临的主要问题和挑战。     

Stable hovering of a jellyfish-like flying machine

Ornithopters, or flapping-wing aircraft, offer an alternative to helicopters in achieving manoeuvrability at small scales, although stabilizing such aerial vehicles remains a key challenge. Here, we present a hovering machine that achieves self-righting flight using flapping wings alone, without relying on additional aerodynamic surfaces and without feedback control. We design, construct and test-fly a prototype that opens and closes four wings, resembling the motions of swimming jellyfish more so than any insect or bird. Measurements of lift show the benefits of wing flexing and the importance of selecting a wing size appropriate to the motor. Furthermore, we use high-speed video and motion tracking to show that the body orientation is stable during ascending, forward and hovering flight modes. Our experimental measurements are used to inform an aerodynamic model of stability that reveals the importance of centre-of-mass location and the coupling of body translation and rotation. These results show the promise of flapping-flight strategies beyond those that directly mimic the wing motions of flying animals.