Modeling and Trajectory Tracking Control for Flapping-Wing Micro Aerial Vehicles

This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles(FWMAVs)in the longitudinal plane.First of all,the kinematics and dynamics of the FWMAV are established,wherein the aerodynamic force and torque generated by flapping wings and the tail wing are explicitly formulated with respect to the flapping frequency of the wings and the degree of tail wing inclination.To achieve autonomous tracking,an adaptive control scheme is proposed under the hierarchical framework.Specifically,a bounded position controller with hyperbolic tangent functions is designed to produce the desired aerodynamic force,and a pitch command is extracted from the designed position controller.Next,an adaptive attitude controller is designed to track the extracted pitch command,where a radial basis function neural network is introduced to approximate the unknown aerodynamic perturbation torque.Finally,the flapping frequency of the wings and the degree of tail wing inclination are calculated from the designed position and attitude controllers,respectively.In terms of Lyapunov's direct method,it is shown that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin.Simulations are carried out to verify the effectiveness of the proposed control scheme.

Stress Analysis of Membrane Flapping-Wing Aerial Vehicle Based on Different Material Models

Recent studies of flapping-wing aerial vehicles have been focused on the aerodynamic performance based on linear materials. Little work has been done on structural analysis based on nonlinear material models. A stress analysis is conducted in this study on membrane flapping-wing aerial vehicles using finite element method based on three material models, namely, linear elastic, Mooney-Rivlin non linear, and composite material models. The purpose of this paper is to understand how different types of materials affect the stresses of a flapping-wing. In the finite element simulation, each flapping cycle is divided into twelve stages and the maximum stress is calculated in each stage. The results show that 1) there are two peak stress values in one flapping cycle;one at the beginning stage of down stroke and the other at the beginning of upstroke, 2) maximum stress at the beginning of down stroke is greater than that at the beginning of upstroke, 3) maximum stress based on each material model is different. The composite and the Mooney-Rivlin nonlinear models produce much less stresses compared to the linear material model;and 4) the ratio of downstroke maximum stress and upstroke maximum stress varies with different material models. This research is helpful in answering why insect wings are so impeccable, thus providing a possibility of improving the design of flapping-wing aerial vehicles.

Aerodynamic Analysis and Simulation of Flapping Wing Aerial Vehicles on Hovering

In order to design and verify control algorithms for flapping wing aerial vehicles(FWAVs),calculation models of the translational force,rotational force and virtual mass force were established with the basis on the modified quasi-steady aerodynamic theory and high lift mechanisms of insect flight.The simulation results show that the rotational force and virtual mass force can be ignored in the hovering FWAVs with simple harmonic motions in a cycle.The effects of the wing deformation on aerodynamic forces were investigated by regarding the maximum rotational angle of wingtip as a reference variable.The simulation results also show that the average lift coefficient increases and drag coefficient decreases with the increase of the maximum rotational angle of wingtip in the range of 0-90°.

Topology optimization in lightweight design of a 3D-printed flapping-wing micro aerial vehicle

Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions,especially for a tiny Flapping-wing Micro Aerial Vehicle(FMAV)transmission system manufactured by 3D printing.In this paper,experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system.First,the constitutive behavior of the ultraviolet(UV)curable resin used in fabrication was evaluated.Second,a numerical computation model describing further verified via experiments.Topology optimization modeling considering nonlinear factors,e.g.contact,friction and collision,was presented,and the optimization results were verified by both dynamic simulation and experiments.Finally,detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization.Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.

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。

A Miniature Video Stabilization System for Flapping-Wing Aerial Vehicles

In this paper,a miniature video stabilization system is designed to deal with the image jitter and motion blur problem for°apping-wing aerial vehicles(FWAVs).First,a light and two-axis pan–tilt(about 13 g)is built for the FWAV to counteract most of the jitter e®ect.Then,an electronic image stabilization method combined with a Micro-Electro Mechanical Systems(MEMSs)gyroscope is proposed to further stabilize the images.Finally,°ight experiment results show that the designed video stabilization system e®ectively improves the quality of aerial videos.

Development of a Bird-like Flapping-wing Aerial Vehicle with Autonomous Take-off and Landing Capabilities

The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results on the autonomous take-off and landing technology of unmanned aerial vehicles,four types of technologies are studied,including jumping take-off and landing technology,taxiing take-off and landing technology,gliding take-off and landing technology,and vertical take-off and landing(VTOL)technology.Based on the analytic hierarchy process(AHP)-comprehensive evaluation method,a fuzzy comprehensive evaluation model for the autonomous take-off and landing scheme of a BFAV is established,and four schemes are evaluated concretely.The results show that under the existing technical conditions,the hybrid layout VTOL scheme is the best.Furthermore,the detailed design and development of the prototype of a BFAV with a four-rotor hybrid layout are carried out,and the vehicle performance is tested.The results prove that through the four-rotor hybrid layout design,the BFAV has good autonomous take-off and landing abilities.The power consumption analysis shows that for a fixed-point reconnaissance mission,when the mission radius is less than 3.38 km,the VTOL type exhibits longer mission duration than the hand-launched type.

基于仿生技术的尾座式VTOL无人机起降稳定控制及轨迹优化

尾座式垂直起降(Vertical takeoff/landing,VTOL)无人机(Unmanned aerial vehicle,UAV)稳定性差,与传统起落架的适配性低。针对上述问题,提出了一种采用自由尾翼技术的新型起落架。该起落架采用串联多级结构,在降低机身高度的同时,保证了巡航状态下尾翼力臂的长度,并通过虚拟中心点力分布技术对动态着陆过程进行调控,简化了控制过程,有利于模式转换过程中的无缝轨迹优化。随后基于猫中心点单点数据集,利用神经网络对起落架控制进行训练,有效提高了起落架自适应起落速度和精度。最后,结合无人机不同模式的参数要求,进行多目标优化和相似性转换,有效提高了尾座式垂直起降无人机的着陆适应性和稳定性。

用于无人机自主定位的仿生视觉路标获取方法

为了解决无人机自主定位时高鲁棒性路标获取问题,提出一种仿生视觉路标获取方法。首先构建多尺度多方向的Gabor滤波器模拟视皮层简单细胞响应,通过MAX操作实现对简单细胞空间位置和方向的选择,然后对提取出的特征点采用基于分块信息熵的方法选择合理的关键点作为路标用于定位。仿真分析结果表明,提出的特征提取方法能够更好地保留图像局部区域的主要信息,具有较好的尺度不变性、旋转不变性以及抗噪声性能,基于分块信息熵方法选出的关键点作为路标用于无人机自主定位精度也较高。

小型无人机气动肌腱式弹射系统动态仿真与优化

针对冲击气缸式无人机弹射系统耗气量高、质量大、动态特性差等弊端,提出了一种仿生气动肌腱式无人机弹射系统,利用气动肌腱的弱非线性,通过配置楔角以改善无人机加速阶段的受力情况,减缓加速度波动。对该弹射系统进行数学建模和动力学分析,并搭建Simulink模型对该系统进行仿真求解;通过MATLAB与Simulink对现有加速轨道通过多目标遗传算法实现进一步优化。优化后的加速轨道能提升加速度均值、气动肌腱能量利用率和起飞速度,且降低了加速度峰值,加速度波动在原有基础上降低了76.79%。仿真和优化结果表明,提出的气动肌腱式无人机弹射系统不仅避免了冲击气缸式弹射系统的缺点,还能进一步平缓加速度,减小整体系统的最大过载。

仿翠鸟水空跨介质航行器设计与入水分析

为了满足水空跨介质航行器的推进需求,精简其动力系统,仿翠鸟设计由单一动力源驱动的水空跨介质航行器.通过计算流体力学(CFD)软件仿真分析入水高度、入水角度和航行器密度等关键影响因素对航行器入水速度、深度和冲击加速度等动力学性能的影响,并与自然界翠鸟的入水性能进行对比.结果表明:在入水角度一定时,增加入水高度将导致航行器所受的冲击加速度增量与入水深度增量的比值增大,从而提高相同条件下对结构强度的要求;在一定范围内航行器密度的增加有利于降低对结构强度的要求;当入水角度约为45°~60°时,所需结构强度最低.在入水深度满足要求的情况下,应适当增大航行器的密度、减小入水高度,且航行器的最佳入水角度为45°~60°.

机械与运载工程领域颠覆性技术战略研究

通过文献研究和专家访谈等方法,提出机械与运载工程领域已有或潜在的颠覆性技术:仿生智能技术、无轴轮缘推进技术、智能无人飞行器技术、超回路列车技术和微机电系统,对这五项技术的创新性和颠覆性优势进行了分析,最后提出机械与运载领域颠覆性技术的发展建议。

无人机集群智能的生成样式研究

无人机集群作战是未来的重要作战方式。无人机集群智能的生成模式及其应用实现途径等智能生成样式问题研究是无人机集群作战编成确定和作战运用设计的基础支撑。归纳提出了无人机集群智能的集中式、仿生行为式和功能分布式生成模式,并从总体上探讨了相应的应用实现途径;提出了基于平行系统架构的战中任务调整和航路再规划智能效果实现途径;研究提出了仿生行为智能涌现运用于陌生环境下航路搜索、攻击与优化的方法途径。

仿生扑翼飞行器风洞实验研究进展

仿生扑翼飞行器的设计灵感来源于自然界中的鸟类、昆虫和蝙蝠的飞行模式,通过机翼的主动运动来产生飞行所需要的升力和推力.仿生扑翼飞行器具有隐蔽性好、机动性强等优点,成为近年来国内外飞行器研究的重点.但是仿生扑翼飞行器研究涉及到低雷诺数、非定常空气动力学等问题,与常规固定翼飞行器有很大的不同.仿生扑翼飞行器的研究方法一般分三种:气动计算、风洞实验和外场试飞.气动计算方面,非定常气动设计优化理论与方法目前仍存在不足;外场试飞的方法无法精确测量出飞行器复杂的气动力,难以对飞行器进行定量分析研究;风洞实验由于可以模拟飞行时的真实情况,获得的数据较为真实可靠,且可以定量分析研究,成为目前研究仿生扑翼飞行器非常有效的方法.国内外研究人员利用风洞进行了大量针对仿生扑翼飞行器的实验研究.在介绍了风洞组成和分类的基础上,详细阐述了仿鸟和仿昆虫扑翼飞行器风洞实验的研究现状,最后对仿生扑翼飞行器风洞实验未来可能的研究方向给出了建议.

仿生扑翼飞行器能耗研究进展

自然界中飞行生物利用肌肉、骨骼等结构的协同作用实现灵活、敏捷的飞行,具有扑动、悬停、滑翔等多种飞行模式.仿生扑翼飞行器是模拟鸟类和昆虫等飞行模式的一类飞行器,通过机翼的周期性上下扑动产生飞行所需的升力和推力,具有隐蔽性好、能效高和飞行噪声小等优点,得到了各研究机构的广泛关注.由于扑翼飞行器自身的负载能力较小,很难携带大容量的电池,导致其续航时间有限.研究新型轻质高能量密度的电池和高仿生设计实现续航时间的提升,是扑翼飞行器重要的研究方向.但是,针对扑翼飞行器新型电池的研究还处于初级研发阶段,尚不具备机载飞行测试的能力.研究人员从仿生机理分析、机构优化设计以及控制策略研究等方面入手,针对扑翼飞行器能耗问题开展了大量研究,并取得了阶段性成果.总结了有关仿生扑翼飞行器能耗方面的研究进展,分析了静态参数、动态参数和控制策略等对仿生扑翼飞行器能耗的影响,提出了降低能耗的措施,并对未来研究方向做出了展望.

面向环境探测的多智能体自组织目标搜索算法

针对在复杂非结构化环境下如何协调多个无人机发现静态或动态目标的问题,建立了自组织目标搜索算法框架。结合磁探仪等效平均探测宽度模型,受昆虫协调方式和鸟群效应的生物机制启发,提出了基于仿生集群算法的无人机集群分布式目标搜索模型;采用改进的自适应差分进化算法帮助无人机集群模型在环境中平衡勘探和探索,实现无人机群体的协同搜索优化。该自组织目标搜索算法旨在以最短时间实现跟踪目标数量的最大化。基于仿真平台的实验测试了该策略的性能,验证了算法对具有未知目标的非结构化复杂环境的适用性。

音频感知哈希闭环检测的无人机仿生声呐SLAM算法研究

针对基于SLAM技术无人机在特定高度下构建二维经历图的优化问题,在RatSLAM的基础上,采用仿生声呐系统代替视觉传感器的BatSLAM模型和音频感知哈希闭环检测,实现在暗光条件下的二维经历图优化。BatSLAM模型通过绝对差值和(SAD)图像处理方法来进行仿生声纳模板的更新,此方法仅仅判断二幅耳蜗图外观是否一致,不存在几何处理和特征提取。由于耳蜗图在获取和传输过程中会产生各类噪音,相同位置获得的耳蜗图具有一定的差异,会导致构建的经历图失真。本文在BatSLAM的基础上,使用音频感知哈希算法对耳蜗图进行特征提取,并进行闭环检测。改进后的算法不仅考虑到外观,而且考虑到相邻频带间的能量差异,通过提高闭环检测准确率,来改善经历图的失真问题。仿真实验表明:采用基于音频感知哈希闭环检测的BatSLAM模型,不仅实现了无人机特定高度和暗光条件下二维经历图的构建,而且提高了闭环检测准确率,从而改善经历图的失真问题,实现经历图的优化。

折叠翼飞行器设计与气动仿真分析

为提高扑翼飞行器的气动效率,分析自然界鸟类翅膀运动机理,设计拍打-折叠运动的仿鸟飞行器机构,实现了仿鸟翅膀“8”字型运动轨迹。区别于传统扑翼飞行器的膜状翼结构,模仿鸟类翅膀羽毛分层结构,研制出羽毛机翼。利用计算流体力学仿真软件XFlow,研究机翼初始迎角,展弦比和扑动频率对折叠翼扑翼飞行器的气动特性影响。实验结果表明:机翼初始迎角在5°时取得最大升阻比系数,有利于飞行器快速升空及平飞飞行;扑动频率在4~5 Hz时获得最佳气动效率;机翼展弦比为3,扑翼飞行器获得较优气动性能。羽翼动力折叠翼飞行器成功飞行,为研制机翼多自由度变形仿生机器鸟提供理论上的可行性和有效飞行平台。

HIT-Hawk and HIT-Phoenix: Two kinds of flapping-wing flying robotic birds with wingspans beyond 2 meters

Inspired by large and medium-sized birds,two kinds of flapping-wing flying robots with wingspans beyond 2 meters were developed.They have the appearance of a hawk and a phoenix respectively,so they are called HIT-Hawk and HIT-Phoenix.In this paper,the bionic concept,theoretical analysis,design and manufacturing are introduced in detail.Firstly,the flight principle and characteristics of large and medium-sized birds were summarized.Then,the aerodynamics was modeled based on the thin airfoil theory,and the main design basis was established.Secondly,the mechanical structures of HIT-Hawk and HIT-Phoenix were designed to ensure the lateral and longitudinal stability and have optimized flight performance.Moreover,an autonomous flight control method was proposed and realized in highly integrated on-onboard controller;it satisfies the strict restrictions on mass,size,power and shape.Finally,the prototypes were fabricated and verified through practical flight experiments.The wingspans of these two flapping wing aircrafts are 2.0 m and 2.3 m respectively,the take-off weights are 1.15 kg and 0.86 kg,and the maximum stable endurance is 65 min(with battery of 3S LiPo,4300 mAh)and 8 min(with battery of 3S LiPo,800 mAh).Their wind resistance can both reach level 4.Compared with the small and micro flapping-wing aerial vehicles that mimic insects or small birds,they both have strong load capacity,strong wind resistance and long endurance.

Study on the Vibration Reduction Characteristics of FWMAV Flexible Bionic Wings Mimicking the Hindwings of Trypoxylus dichotomus

Using the method of structural finite element topology optimization and analysis of the hindwings of Trypoxylus dichotomus,this work identified the main loading force transmission path and designed the initial structure of a bionic flexible wing.A structural design scheme of the vibration damping unit was proposed,and the structural mechanics and modal vibration characteristics were simulated and analyzed.3D printing technology was used to manufacture the designed bionic wing skeleton,which was combined with two kinds of wing membrane materials.The Flapping Wing Micro-aerial Vehicle(FWMAV)transmission mechanism vibration characteristics were observed and analyzed by a high-speed digital camera.A triaxial force transducer was used to record the force vibration of the flexible bionic wing flapping in a wind tunnel.A wavelet processing method was used to process and analyze the force signal.The results showed that the force amplitude was more stable,the waveform roughness was the lowest,and the peak shaving phenomenon at the z-axis was the least obvious for the bionic flexible wing model that combined the topology-optimized bionic wing skeleton with a polyamide elastic membrane.This was determined to be the most suitable design scheme for the wings of FWMAVs.