Human Memory/Learning Inspired Control Method for Flapping-Wing Micro Air Vehicles

The problem of flapping motion control of Micro Air Vehicles (MAVs) with flapping wings was studied in this paper.Based upon the knowledge of skeletal and muscular components of hummingbird, a dynamic model for flapping wing wasdeveloped.A control scheme inspired by human memory and learning concept was constructed for wing motion control ofMAVs.The salient feature of the proposed control lies in its capabilities to improve the control performance by learning fromexperience and observation on its current and past behaviors, without the need for system dynamic information.Furthermore,the overall control scheme has a fairly simple structure and demands little online computations, making it attractive for real-timeimplementation on MAVs.Both theoretical analysis and computer simulation confirms its effectiveness.

Kinematic and Aerodynamic Modelling of Bi- and Quad-Wing Flapping Wing Micro-Air-Vehicle

A generic approach to model the kinematics and aerodynamics of flapping wing ornithopter has been followed, to model and analyze a flapping bi- and quad-wing ornithopter and to mimic flapping wing biosystems to produce lift and thrust for hovering and forward flight. Considerations are given to the motion of a rigid and thin bi-wing and quad-wing ornithopter in flapping and pitching motion with phase lag. Basic Unsteady Aerodynamic Approach incorporating salient features of viscous effect and leading-edge suction are utilized. Parametric study is carried out to reveal the aerodynamic characteristics of flapping bi- and quad-wing ornithopter flight characteristics and for comparative analysis with various selected simple models in the literature, in an effort to develop a flapping bi- and quad-wing ornithopter models. In spite of their simplicity, results obtained for both models are able to reveal the mechanism of lift and thrust, and compare well with other work.

Development of Air Vehicle with Active Flapping and Twisting of Wing

This paper addresses mechanisms for active flapping and twisting of robotic wings and assesses flying effectiveness as a function of twist angle. Unlike the flapping motion of bird wings, insects generally make a twisting motion at the root of their wings while flapping, which makes it possible for them to hover in midair. This work includes the development of a Voice Coil Motor （VCM） because a flapping-wing air vehicle should be assembled with a compact actuator to decrease size and weight. A linkage mechanism is proposed to transform the linear motion of the VCM into the flapping and twisting motions of wings. The assembled flapping-wing air vehicle, whose weight is 2.86 g, produces an average positive vertical force proportional to the twist angle. The force saturates because the twist angle is mechanically limited. This work demonstrates the possibility of developing a flapping-wing air vehicle that can hover in midair using a mechanism that actively twists the roots of wings during flapping.

Piezoelectric energy harvesting from morphing wing motions for micro air vehicles

Wing flapping and morphing can be very beneficial to managing the weight of micro air vehicles through coupling the aerodynamic forces with stability and control. In this letter, harvesting energy from the wing morphing is studied to power cameras, sensors, or communication devices of micro air vehicles and to aid in the management of their power. The aerodynamic loads on flapping wings are simulated using a three-dimensional unsteady vortex lattice method. Active wing shape morphing is considered to enhance the performance of the flapping motion. A gradient-based optimization algorithm is used to pinpoint the optimal kinematics maximizing the propellent efficiency. To benefit from the wing deformation, we place piezoelectric layers near the wing roots. Gauss law is used to estimate the electrical harvested power. We demonstrate that enough power can be generated to operate a camera. Numerical analysis shows the feasibility of exploiting wing morphing to harvest energy and improving the design and performance of micro air vehicles.

The effect of phase angle and wing spacing on tandem flapping wings

In a tandem wing configuration, the hindwing of- ten operates in the wake of the forewing and, hence, its per- formance is affected by the vortices shed by the forewing. Changes in the phase angle between the flapping motions of the fore and the hind wings, as well as the spacing between them, can affect the resulting vortex/wing and vortex/vortex interactions. This study uses 2D numerical simulations to in- vestigate how these changes affect the leading dege vortexes （LEV） generated by the hindwing and the resulting effect on the lift and thrust coefficients as well as the efficiencies. The tandem wing configuration was simulated using an incom- pressible Navier-Stokes solver at a chord-based Reynolds number of 5 000. A harmonic single frequency sinusoidal oscillation consisting of a combined pitch and plunge motion was used for the flapping wing kinematics at a Strouhal num- ber of 0.3. Four different spacings ranging from 0.1 chords to 1 chord were tested at three different phase angles, 0°, 90° and 180°. It was found that changes in the spacing and phase angle affected the timing of the interaction between the vor- tex shed from the forewing and the hindwing. Such an inter- action affects the LEV formation on the hindwing and results in changes in aerodynamic force production and efficiencies of the hindwing. It is also observed that changing the phase angle has a similar effect as changing the spacing. The re- suits further show that at different spacings the peak force generation occurs at different phase angles, as do the peak efficiencies.

Review on ultra-lightweight flapping-wing nano air vehicles:Artificial muscles,flight control mechanism,and biomimetic wings

Flying insects are capable of flapping their wings to provide the required power and control forces for flight.A coordinated organizational system including muscles,wings,and control architecture plays a significant role,which provides the sources of inspiration for designing flapping-wing vehicles.In recent years,due to the development of micro-and meso-scale manufacturing technologies,advances in components technologies have directly led to a progress of smaller Flapping-Wing Nano Air Vehicles(FWNAVs)around gram and sub-gram scales,and these air vehicles have gradually acquired insect-like locomotive strategies and capabilities.This paper will present a selective review of components technologies for ultra-lightweight flapping-wing nano air vehicles under 3 g,which covers the novel propulsion methods such as artificial muscles,flight control mechanisms,and the design paradigms of the insect-inspired wings,with a special focus on the development of the driving technologies based on artificial muscles and the progress of the biomimetic wings.The challenges involved in constructing such small flapping-wing air vehicles and recommendations for several possible future directions in terms of component technology enhancements and overall vehicle performance are also discussed in this paper.This review will provide the essential guidelines and the insights for designing a flapping-wing nano air vehicle with higher performance.

An experimental study of elastic properties of dragonfly-like flapping wings for use in biomimetic micro air vehicles(BMAVs)

This article studies the elastic properties of several biomimetic micro air vehicle（BMAV）wings that are based on a dragonfly wing.BMAVs are a new class of unmanned micro-sized air vehicles that mimic the flapping wing motion of flying biological organisms（e.g.,insects,birds,and bats）.Three structurally identical wings were fabricated using different materials：acrylonitrile butadiene styrene（ABS）,polylactic acid（PLA）,and acrylic.Simplified wing frame structures were fabricated from these materials and then a nanocomposite film was adhered to them which mimics the membrane of an actual dragonfly.These wings were then attached to an electromagnetic actuator and passively flapped at frequencies of 10-250 Hz.A three-dimensional high frame rate imaging system was used to capture the flapping motions of these wings at a resolution of 320 pixels x 240 pixels and 35000 frames per second.The maximum bending angle,maximum wing tip deflection,maximum wing tip twist angle,and wing tip twist speed of each wing were measured and compared to each other and the actual dragonfly wing.The results show that the ABS wing has considerable flexibility in the chordwise direction,whereas the PLA and acrylic wings show better conformity to an actual dragonfly wing in the spanwise direction.Past studies have shown that the aerodynamic performance of a BMAV flapping wing is enhanced if its chordwise flexibility is increased and its spanwise flexibility is reduced.Therefore,the ABS wing（fabricated using a 3D printer） shows the most promising results for future applications.

仿绿头鸭扑翼飞行器的低速飞行气动特性仿真研究

针对仿绿头鸭扑翼飞行器,在刚性扑动基础上引入了展向弯折和弦向扭转两种运动方式,提出了4种不同扑动路径的描述方程,并对其低速飞行气动特性进行了研究。首先,根据绿头鸭翼翅外形选择NACA 6411翼型并对其弯度和长度进行修正,通过放样创建扑翼几何构型。之后,基于动网格技术构建扑翼流场网格模型,包含刚性扑动、机翼弯折和机翼扭转等3种不同扑动形态。最后,使用Fluent进行瞬态仿真,基于压力耦合求解器和k-ω湍流模型得到不同扑动形态下飞行速度为2 m/s时的气动特性。结果表明,在低速飞行时,非对称扑动效应、展向弯折效应和弦向扭转效应均可起到增加升力、降低阻力的效果。所提出的3个扑动模型相对传统的对称刚性扑动模型分别能提高3.89%、14.78%、24.44%的升力,其中弯扭组合形式的扑动提供的推力能够抵消前飞时的空气阻力。

Structural Characteristics of Allomyrina Dichotoma Beetle＇s Hind Wings for Flapping Wing Micro Air Vehicle

In this study, we present a complete structural analysis ofAllomyrina dichotoma beetle＇s hind wings by investigating their static and dynamic characteristics. The wing was subjected to the static loading to determine its overall flexural stiffness. Dy- namic characteristics such as natural frequency, mode shape, and damping ratio of vibration modes in the operating frequency range were determined using a Bruel ＆ Kjaer fast Fourier transform analyzer along with a laser sensor. The static and dynamic characteristics of natural Allomyrina dichotoma beetle＇s hind wings were compared to those of a fabricated artificial wing. The results indicate that natural frequencies of the natural wing were significantly correlated to the wing surface area density that was defined as the wing mass divided by the hind wing surface area. Moreover, the bending behaviors of the natural wing and artificial wing were similar to that of a cantilever beam. Furthermore, the flexural stiffness of the artificial wing was a little higher than that of the natural one whereas the natural frequency of the natural wing was close to that of the artificial wing. These results provide important information for the biomimetic design of insect-scale artificial wings, with which highly ma- neuverable and efficient micro air vehicles can be designed.

Generation of Control Moments in an Insect-like Tailless Flapping-wing Micro Air Vehicle by Changing the Stroke-plane Angle

We propose a control moment generator to control the attitude of an insect-like tailless Flapping-wing Micro Air Vehicle （FW-MAV）, where the flapping wings simultaneously produce the flight force and control moments. The generator tilts the stroke plane of each wing independently to direct the resultant aerodynamic force in the desired direction to ultimately generate pitch and yaw moments. A roll moment is produced by an additional mechanism that shifts the trailing edge, which changes the wing rotation angles of the two flapping wings and produces an asymmetric thrust. Images of the flapping wings are captured with a high-speed camera and clearly show that the FW-MAV can independently change the stroke planes of its two wings. The measured force and moment data prove that the control moment generator produces reasonable pitch and yaw moments by tilting the stroke plane and realizes a roll moment by shifting the position of the trailing edge at the wing root.

Design and Aerodynamic Analysis of Dragonfly-like Flapping Wing Micro Air Vehicle

Dragonflies have naturally high flying ability and flight maneuverability,making them more adaptable to harsh ecological environments.In this paper,a flapping wing bionic air vehicle with three-degrees-of-freedom is designed and manufactured by simulating the flight mode of dragonfly.Firstly,the body structure of dragonfly was analyzed,and then the design scheme of flapping wing micro air vehicle was proposed based on the flight motion characteristics and musculoskeletal system of dragonfly.By optimizing the configuration and using Adams to do kinematic simulation,it is shown that the designed structure can make the wings move in an“8”shape trajectory,and the motion in three directions can maintain good consistency,with good dynamic performance.Based on CFD simulation method,we analyzed that the wing has the conditions to achieve flight with good aerodynamic performance at the incoming flow speed of 5 m s^(-1)and frequency of 4 Hz,and studied the effects of angle of attack and flutter frequency on the aerodynamic performance of the aircraft.Finally,the force measurement test of the aircraft prototype is carried out using a force balance and a small wind tunnel.The test results show that the prototype can provide the average lift of 3.62 N and the average thrust of 2.54 N,which are in good agreement with the simulation results.

蝴蝶飞行机理及仿蝴蝶扑翼飞行器研究进展综述

仿生扑翼飞行器具有高机动性、高隐蔽性以及高效率等突出优势,在军事侦查、探险搜救等领域具有较好的应用前景,而其应用的基础是对生物飞行机理的深入探究.随着先进运动观测和实验技术的引入,对昆虫飞行行为的记录和分析更为便捷和准确.研究表明常见的昆虫拍打频率较高,在25~400 Hz之间,而蝴蝶较为特殊,其扑打频率较低,大约为10 Hz,对于蝴蝶的许多独特的飞行技能尚缺少足够的认识.蝴蝶前翼和后翼的翼面积都较大,身体同侧的前后翼几乎为同步拍打,且扑打幅度较大,甚至接近180°.蝴蝶飞行中身体有较大幅度的上下和俯仰震荡,翼和身体运动高度耦合.即便如此,蝴蝶仍具有敏捷的飞行能力,可以达到点对点的飞行目标,甚至上千公里的长途迁徙,是优秀的仿生学研究对象.因此,蝴蝶启发的仿生扑翼飞行器也得到了全世界研究人员的关注.蝴蝶的飞行机制相对于其他昆虫更加特殊,飞行行为和气动特性更为复杂,这使得仿蝴蝶扑翼飞行器的研制更加困难.目前对于仿蝴蝶飞行器的研制大多数对蝴蝶翼–身耦合的机理进行了简化,很少能实现受控的稳定飞行.最后,本文梳理了真实蝴蝶的飞行行为特点和飞行机理,指出了仿蝴蝶扑翼飞行器研制的关键技术,总结了该类飞行器未来的发展方向和应用前景.

具有不确定性的扑翼微型飞行器抗干扰控制

研究了具有内部不确定性和外部干扰的扑翼微型飞行器的姿态和位置跟踪控制问题。利用神经网络对扑翼微型飞行器数学模型中复杂非线性和不确定性进行逼近估计,同时对于外部扰动,采用自适应技术来处理干扰对系统的影响。基于反步递推框架,引入一阶滤波器,设计了动态表面控制器,克服了传统反步递推设计中“微分爆炸”的局限性。进一步,利用Lyapunov稳定理论证明了扑翼飞行器姿态和位置闭环系统的稳定性和所有状态变量的半全局一致最终有界性。结果表明,所提控制器不仅能够使稳态误差更好地收敛,而且还提高了收敛速度。仿真结果验证了所提控制方法能够有效地处理不确定性和外部干扰,且能够很好地跟踪期望轨迹。

Computational aerodynamics of low Reynolds number plunging,pitching and flexible wings for MAV applications

Micro air vehicles （MAV＇s） have the potential to revolutionize our sensing and information gathering capabilities in environmental monitoring and homeland security areas. Due to the MAV＇s＇ small size, flight regime, and modes of operation, significant scientific advancement will be needed to create this revolutionary capability. Aerodynamics, structural dynamics, and flight dynamics of natural flyers intersects with some of the richest problems in MAV＇s, inclu- ding massively unsteady three-dimensional separation, transition in boundary layers and shear layers, vortical flows and bluff body flows, unsteady flight environment, aeroelasticity, and nonlinear and adaptive control are just a few examples. A challenge is that the scaling of both fluid dynamics and structural dynamics between smaller natural flyer and practical flying hardware/lab experiment （larger dimension） is fundamentally difficult. In this paper, we offer an overview of the challenges and issues, along with sample results illustrating some of the efforts made from a computational modeling angle.

Design and experimental study of a new flapping wing rotor micro aerial vehicle

A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift,and control mechanisms are designed to control the pose of the FWR-MAV.A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight.A series of flight tests was conducted,with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV.The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space;the experiment of forward flight shows that the FWR-MAV can track the desired attitude.

Flapping wing micro-aerial-vehicle： Kinematics, membranes, and flapping mechanisms of ornithopter and insect flight

The application of biomimetics in the development of unmanned-aerial-vehicles （UAV） has advanced to an exceptionally small scale of nano-aerial-vehicles （NAV）, which has surpassed its immediate predecessor of micro-aerial-vehicles （MAV）, leaving a vast range of development possi- bilities that MAVs have to offer. Because of the prompt advancement into the NAV research devel- opment, the true potential and challenges presented by MAV development were never solved, understood, and truly uncovered, especially under the influence of transition and low Reynolds number flow characteristics. This paper reviews a part of previous MAV research developments which are deemed important of notification; kinematics, membranes, and flapping mechanisms ranges from small birds to big insects, which resides within the transition and low Reynolds number regimes. This paper also reviews the possibility of applying a piezoelectric transmission used to pro- duce NAV flapping wing motion and mounted on a MAV, replacing the conventional motorized flapping wing transmission. Findings suggest that limited work has been done for MAVs matching these criteria. The preferred research approach has seen bias towards numerical analysis as compared to experimental analysis.

Co-simulation and Experimental Study for Wingspan of Flapping Wing Micro Aerial Vehicle

The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.

Tensile Properties of Veins of Damselfly Wing

Microtension test of Costa and Radius veins of damselfly wing was conducted to measure tensile strength and modulus. The specimens were classified into fresh and dry depending on when the samples were prepared and tested. Fresh samples tested immediately after extracting from the fly while the dry samples were tested one year after extraction and stored in a desiccator. Measured load-displacement response and fracture load were used to calculate modulus and strength. Field Emission Scanning Electron Microscope was used to measure the fracture morphology and cross-section of the vein. The results showed that the veins are brittle and fracture surface is flat. The average strength (232 - 285 MPa) and modulus (14 - 17 GPa) of the Costa and Radius veins were nearly same for both fresh and dry samples. The tensile modulus of the veins was 8% - 10% higher than the indentation (compressive) modulus and was nearly the same as that of human bones.

可悬停扑翼飞行器研究现状与关键技术

可悬停扑翼飞行器模仿自然界定点滞空昆虫和鸟类的飞行特点,隐蔽性高、灵活机动、应用环境多样,具有突出的理论和实用价值,引起了世界范围的广泛关注。对可悬停扑翼飞行器的研究现状和发展方向进行了综合评述。首先总结了近年来最突出的研究成果,按照微扑翼尺寸分类分别介绍MAV、NAV、PAV尺度下可悬停扑翼微飞行器的样机构型、动力系统、质量分配与飞行性能,统计了升力、翼展、质量、扑翼幅值等重要参数,介绍了电机、压电和电磁驱动扑翼微飞行器最具代表性的研究工作;然后针对目前飞行器研究运用的升力产生原理、飞行稳定性分析、功耗效率优化、续航能力等关键技术进行了分析和总结;最后讨论了扑翼飞行器亟待突破的技术难题和未来发展方向。

突风扰动下的扑翼气动功耗和效率变化

针对突风对扑翼飞行器气动性能的影响,开展了前向、侧向和竖直方向突风中扑翼的气动功耗和效率变化研究。首先基于简化的生物翅几何和运动模型,构建了不同方向、强度的突风模型。之后采用计算流体力学方法获得了突风方向及强度对扑翼气动力、功耗及效率的影响。最终结果表明,在所研究的突风强度范围内,前向突风引起的扑翼瞬时气动功耗增幅可达33%,但突风对扑翼平均气动功耗和效率的影响不大;从翼根到翼尖的侧向突风相比反方向的侧向突风所引起的气动功耗增加和气动效率降低更加明显;向下的突风尽管能够降低扑翼的气动功耗,但也同时降低了扑翼的气动效率。此外,突风对扑翼平均气动功耗的影响可以用与突风方向相同、大小等于突风平均速度的定常来流进行模拟,它们对扑翼平均气动功耗的影响是相近的。