Transonic Rudder Buzz on Tailless Flying Wing UAV

Transonic rudder buzz responses based on the computational fluid dynamics or computational structural dynamics(CFD/CSD)loosely method are analyzed for a tailless flying wing unmanned aerial vehicle(UAV).The Reynolds-averaged Navier-Stokes(RANS)equations and finite element methods based on the detailed aerodynamic and structural model are established,in which the aerodynamic dynamic meshes adopt the unstructured dynamic meshes based on the combination of spring-based smoothing and local remeshing methods,and the lower-upper symmetric-Gauss-Seidel(LU-SGS)iteration and Harten-Lax-van Leer-Einfeldt-Wada(HLLEW)space discrete methods based on the shear stress transport(SST)turbulence model are used to calculate the aerodynamic force.The constraints of the rudder motions are fixed at the end of structural model of the flying wing UAV,and the structural geometric nonlinearities are also considered in the flying wing UAV with a high aspect ratio.The interfaces between structural and aerodynamic models are built with an exact match surface where load transferring is performed based on 3Dinterpolation.The flying wing UAV transonic buzz responses based on the aerodynamic structural coupling method are studied,and the rudder buzz responses and aileron,elevator and flap vibration responses caused by rudder motion are also investigated.The effects of attack,height,rotating angular frequency and Mach number under transonic conditions on the flying wing UAV rudder buzz responses are discussed.The results can be regarded as a reference for the flying wing UAV engineering vibration analysis.

A Software-in-the-Loop Implementation of Adaptive Formation Control for Fixed-Wing UAVs

This paper discusses the design and software-in-theloop implementation of adaptive formation controllers for fixedwing unmanned aerial vehicles(UAVs) with parametric uncertainty in their structure, namely uncertain mass and inertia. In fact, when aiming at autonomous flight, such parameters cannot assumed to be known as they might vary during the mission(e.g.depending on the payload). Modeling and autopilot design for such autonomous fixed-wing UAVs are presented. The modeling is implemented in Matlab, while the autopilot is based on ArduPilot, a popular open-source autopilot suite. Specifically, the ArduP ilot functionalities are emulated in Matlab according to the Ardupilot documentation and code, which allows us to perform software-in-the-loop simulations of teams of UAVs embedded with actual autopilot protocols. An overview of realtime path planning, trajectory tracking and formation control resulting from the proposed platform is given. The software-inthe-loop simulations show the capability of achieving different UAV formations while handling uncertain mass and inertia.

Trim Drag Prediction for Blended-Wing-Body UAV Configuration

A rapid method of the trim drag prediction for the blended-wing-body unmanned aerial vehicle(UAV)configuration is proposed.The method consists of four steps.The first step is to parameterizedly model the blended-wing-body UAV configuration;the second is to analyze the aerodynamics of the geometric model;the third is to create aerodynamic surrogate model;and the final step is to predict the trim drag using the surrogate model.Hence,a tool for trim drag prediction is developed by integration of the four steps.The impacts of the allocation of control surfaces,position of gravity center and planform parameters on the trim drag are investigated by using the tool.Results show that using the control surface in outer wing for trim has an advantage of lower trim drag,and the position of gravity center has a primary impact on the trim drag.Moreover,the planform has secondary impacts on the trim drag.

基于UIF-MPC仿真的UAV环航姿态控制研究

为解决无人机(unmanned aerial vehicle,UAV)在算法结构冗杂和未知外部干扰的环境下控制系统操作难度大的问题,提出一种基于UIF-MPC融合的自适应全局快速终端滑模控制方法。考虑到在环境复杂、时间敏感及通信受限条件下给出UAV姿态运动观测模型;提出一种多控制变量交互的UIF-MPC融合滤波姿态算法,利用滤波器和PID控制器对模型不确定性和未知干扰进行补偿;根据UAV性能及饱和控制条件设定姿态设定控制参数并设定目标位置估计均方根误差,带入UIF-MPC模型并与传统单UIF模型进行比较。结果表明UIF-MPC融合模型可以较好融合系统需求,且在运动过程中具有较好的估计精度及机动控制的鲁棒性。

考虑无人机飞行时间的能耗与数据量联合优化

在无线传感网络中运用无人机(unmanned aerial vehicle,UAV)通信进行数据采集是一项有价值的技术。针对UAV在有限时间内的数据采集任务,提出了一种考虑系统数据量、节点传输能耗和UAV飞行能耗的联合优化方案。该方案的决策空间包括UAV轨迹与传输调度,复杂度较高。由于联合优化是NP难问题,基于决策空间降维,将优化过程分为初始轨迹优化和二次轨迹优化两步。针对初始轨迹优化,提出基于贪心算法和禁忌搜索算法的优化方案,实现节点选择并得到UAV初始轨迹;针对二次轨迹优化,运用离散化方法转换原问题,采用逐次凸逼近算法进行优化,得到其有效次优解。仿真结果表明,所提优化方案能够在满足时间约束的前提下,提高UAV采集的数据量,并降低UAV和节点的能耗。

基于Super-Twisting滑模S面的无人机路径跟踪控制

针对小型固定翼无人机在执行任务时跟踪精度低以及容易受外界风影响的问题,设计基于Super-Twisting滑模S面(STSM S-Plane)的路径跟踪控制器,同时采用内外双环控制模式。外环即速度环采用Super-Twisting滑模控制,内环即姿态环采用S面控制。考虑到S面控制求导易导致积分爆炸的问题引入了二阶微分器,并对外界风组成进行建模研究。最后通过空间特殊曲线来验证所设计算法的控制性能。仿真结果表明,所设计的算法可以实现固定翼无人机对期望路径的精确跟踪,并具有良好的鲁棒性和抗干扰性能。

具有飞行包线限制的飞翼无人机鲁棒自适应容错姿态控制

为实现复杂环境下飞翼无人机姿态的精确跟踪控制,考虑参数不确定性、外部扰动、执行器故障及飞行包线限制的影响,提出一种基于Nussbaum增益的鲁棒自适应容错控制方法。在受扰动的飞翼无人机姿态运动学与动力学模型基础上考虑执行器故障与系统不确定的影响,建立面向控制的姿态控制模型。通过引入时变障碍Lyapunov函数,在保证飞行包线限制的同时确保姿态跟踪误差的瞬态与稳态性能。通过自适应的有界估计与Nussbaum增益,补偿总的不确定项与执行器故障的影响。通过稳定性分析严格证明新提出的控制方法的可行性。仿真结果表明,新的控制方法能够确保飞行包线限制,同时保证预设的瞬态与稳态性能,实现飞翼无人机高精度的姿态跟踪控制。

全碳纤维复合材料太阳能无人机机翼结构优化设计

针对大展弦比太阳能无人机的性能要求,开展碳纤维复合材料太阳能无人机机翼的优化设计。选用NACA4412为基准翼型,利用xfoil软件作为气动计算软件,基于NSGA-Ⅱ优化算法进行翼型优化。在此基础上对机翼进行三维建模,采用CFD软件进行气动特性分析,并利用ANSYS Workbench静力学模块对机翼进行流固耦合分析。结果表明:翼型优化后,升力系数提高4.20%,阻力系数降低8.74%,升阻比提高14.18%;在气动载荷作用下,从翼根向翼尖方向压力逐渐增大,翼尖处最大压力相对外界大气压力为242 Pa;在外载荷作用下,最大应力显示在翼根附近,为61.397 MPa,翼变形的最大值为40.262 mm,整体满足太阳能无人机的允许变形量在5%以内即翼尖变形不得大于半翼展长度值的5%的刚度要求。研究结果可为碳纤维复合材料太阳能无人机设计和研制提供理论参考。

无人机短距着陆控制技术研究

研究固定翼无人机短距着陆性能具有十分重要的现实意义。基于对象无人机三种襟翼构型中的着陆襟翼构型,分析以固定油门为基础的传统着陆控制方式存在的缺陷性问题,从动力学角度分析近地段在低速、大姿态状态下各项着陆指标间的相互制约关系,并得出“空速为影响着陆性能的主导诱因”这一重要结论,从动力学角度提出油门速度闭环控制方案。在控制律设计过程中,创新性地采用线性化理论分析和半物理非线性仿真相结合的手段,充分结合工程实践经验,突出了油门速度控制的特殊性与有效性,使着陆性能得到前所未有的提升。

输入受限及干扰下固定翼无人机强化学习控制

针对干扰下输入受限的固定翼无人机系统,提出一种基于Actor-Critic的强化学习控制器。首先,建立干扰下固定翼无人机纵向模型,设计带有积分项的性能函数来评估无人机的飞行状态和系统性能;然后,采用强化学习的Actor-Critic算法结构,用Actor求解最小化策略性能函数的控制律,用Critic实现非线性性能函数的逼近;最后,加入Disturbance网络给无人机施加干扰以测试无人机的抗干扰性能,并采用动量梯度下降算法改善神经网络的学习速度和稳定性来加强无人机控制器的控制性能。仿真实验表明:与传统控制方法相比,提出的强化学习控制器能够在输入受限的情况下更快、更稳定地实现控制。

基于nCode的无人机金属机翼结构疲劳分析

近年来,无人机的发展受到越来越多的关注,其主要部件机翼结构的疲劳分析对无人机的安全飞行起到十分重要的影响。该文通过对无人机机翼结构建模,然后采用流固耦合的方法在ANSYS Workbench中模拟计算出机翼正常飞行状态下的结构应力应变分布和形变情况,并使用应力疲劳分析理论,将机翼强度运算结果结合材料S-N曲线在nCode疲劳分析软件中计算分析该无人机机翼的损伤和疲劳寿命。结果表明,该无人机机翼疲劳寿命的最小值和损伤的最大值都出现在主翼梁与机身连接的根部,为后续无人机机翼结构疲劳设计提供另一种参考方法。

固定翼无人机机翼对接过程的气动力建模与路径优化

针对制约链翼无人机研制和发展的固定翼无人机空中聚合难题,研究了固定翼无人机机翼对接过程的气动力建模与路径优化问题。首先,采用数值升力线方法理论建立了固定翼无人机机翼对接过程的气动力模型,分析了不同相对位置和姿态下无人机的气动耦合效应。在此基础上,将对接过程视为加权的有向最短路径问题,提出了一种基于Dijkstra算法的机翼对接路径规划方法,获得了最佳的机翼对接路径。数值仿真结果表明,该气动力建模方法能够可靠描述机翼对接过程的气动耦合效应,优化得到的路径能够显著降低固定翼无人机机翼对接过程的翼尖涡相互干扰。

基于DDPG算法的旋翼无人机智能跟踪方法

针对旋翼无人机视觉伺服控制可视性约束差与控制效率低的问题,介绍四旋翼无人机的动力学模型与传统视觉伺服的基本原理;针对视觉伺服增益调节问题,提出了一种基于深度强化学习的旋翼无人机视觉伺服控制的马可科夫模型;并结合深度确定性策略梯度(DDPG)算法训练了模型,最终得到线速度和角速度2个解耦的伺服增益。结果表明,与传统的基于图像的视觉伺服(IBVS)方法相比,该方法能保证目标始终在视场中、飞行轨迹平滑、到达目标位置所需时间短,满足旋翼无人机视觉伺服控制可视性约束条件,同时,控制效率比传统控制方法高23.5%。实验中该方法能在复杂的非线性环境中实现精确控制,增加了视觉伺服技术的应用场景。

小型固定翼UAV飞控系统的嵌入式设计

随着小型无人机飞控任务的日趋复杂,传统低性能飞控系统已不能满足需要,对此本文提出一种基于ARM-Linux结构的飞控系统的嵌入式设计方法。设计了基于高性能低功耗嵌入式处理器ARM Cortex-A9芯片IMX6Q的嵌入式飞控系统的硬件设计,该系统集成了9轴MIMU、高度计、空速计和GPS等多种传感器。分析了基于嵌入式Linux的飞控软件开发流程,阐述了移植Linux内核的步骤及基于嵌入式Linux设计的多进程飞行控制软件。最后,通过手控飞行验证了硬件平台的可行性和软件设计方法的合理性。采用嵌入式方法设计飞控系统,使飞控系统具备多任务调度、可移植性好、易于二次开发等特点。

Analysis of VTOL UAV Propellant Technology

Recently, the surge in the interests in unmanned aerial vehicles has soared dra-matically worldwide due to many potential benefits foreseen by this technology. The most widespread use of the commercial drones is a multi-copter form of unmanned aerial vehicle, because of its vertical takeoff and landing (VTOL) capability. However, due to the structural characteristics, it has a disadvantage that the flight time is quite short, which is typically ranging between 15 to 30 minutes. The fixed wing type of unmanned aerial vehicles has a longer flight time and duration, but it is not easy to secure a safe landing space, especially in the city areas. For this reason, demand for vertical fixed take-off and landing aircraft is rapidly increasing throughout the world. This study analyzes the trends and recent development of global VTOL technology and provides a direction into which the current state of the technology should be heading. By comparing the advantage and disadvantage of various VTOP propulsion types, we can clearly identify the most effective form of VTOL propulsion types. Such analysis will be highly beneficial to the drone researchers and scientists in terms of future development.

Development of Autonomous VTOL UAV for Wide Area Surveillance

The drone was developed with the use of unmanned aircraft systems in the initial military sector based on the combination of aerospace technology and information and communication technologies in a variety of usability, including the civilian sectors. Developed for the field of reconnaissance, it is used in both civilian and police sectors as traffic monitoring and high altitude reconnaissance missions. It is used in broadcasting and surveillance, while continuously expanding into the areas of courier delivery and rescue missions. Based on the convergence of aviation technology such as various SW, sensor and flight control to utilize unmanned system and information communication technology, commercialization of related technology is being developed as a very diverse route.?In this paper, we propose and manufacture of?a VTOL UAV. Design process referred to the VTOL development process?that has been devised by us, and actual building of a UAV also applied the same VTOL development concept. In order to understand the aerodynamic characteristics of the aircraft, we have applied the aerodynamic design theory and used the CAE method that can replace the actual wind tunnel test. We tested the selection method and criteria for the internal modules that make up the UAV, and we were able to assemble the product. FW coding of flight control computer was conducted for VTOL control. In addition, we developed a LTE communication module for the long distance flight, and carried out flight experiments with GCS to observe and respond to the flight situation from the ground. Flight test results showed that stable transition flight was possible with broadband.?We could see that the actual performance results were met, compared to our development target values.

基于扩展卡尔曼滤波的固定翼无人机姿态解算方法

针对传统滤波方法各自使用时准确度低、稳定性差的问题,提出了一种基于扩展卡尔曼滤波的固定翼无人机姿态解算方法.在姿态角保持稳定时采用标准扩展卡尔曼滤波算法进行解算,姿态角发生剧烈变化时采用阈值法优化改进扩展卡尔曼滤波算法进行解算.改进方法在扩展卡尔曼滤波的基础上加入互补滤波器,把经过互补滤波和PI控制的误差向量补偿给陀螺仪传感器,加入动态梯度下降法对加速度计传感器的运动加速度加以抑制,将处理后的传感器数据代入扩展卡尔曼滤波方程组,用来解算固定翼无人机的三轴姿态角,可有效减小动态干扰和线性化误差,解算结果稳定性更高.与其他解算方法相比,本文用于三轴姿态角求解的姿态解算方法,静态姿态角误差小于0.6°,动态姿态角后验均方误差仅为0.01,特别是在姿态角度变化较大的时间点,本文解算的过程更加稳定和准确.

基于奇异摄动分解的固定翼无人机抗扰动滑模控制

为了提高固定翼无人机的飞行控制精度,减少系统动态耦合和外界干扰对固定翼无人机飞行控制系统性能的影响,建立了固定翼无人机的奇异摄动模型,在此基础上提出基于干扰观测器的滑模控制方法.首先对固定翼无人机的速度和姿态进行动力学建模,将固定翼无人机的动力学模型转换为奇异摄动模型,再对奇异摄动模型进行快慢分解完成解耦,得到两个降阶非耦合子系统,即以角速度为快变量的快子系统和以速度、姿态为慢变量的慢子系统,分别对角速度回路和速度、姿态回路设计基于干扰观测器的滑模控制器.最后,采用Simulink仿真验证了基于快、慢分解的固定翼无人机滑模控制方法的可行性和有效性.

复合翼无人机不同传感器探测大气温湿度对比

无人机为大气探测的重要平台,为克服固定翼起飞降落条件要求高和旋翼机飞行航时短的问题,中国科学院大气物理研究所中层大气和全球环境探测实验室自主研制了一款新型复合翼无人机。为检验其在近地面探测大气温湿度的能力,于2020年7月28日—8月6日及2021年8月1—6日,在内蒙古自治区正镶白旗无人机综合验证基地开展了两期无人机搭载不同传感器探测温湿度的比对试验。结果显示:机载自动站与GPS探空仪所测温度绝对偏差为2.00℃~2.35℃,系统偏差可订正;两者所测相对湿度绝对偏差为4.28%;2021年搭载维萨拉温湿探头,测量对比表明维萨拉温湿探头与GPS探空仪测量结果一致性较好,机载自动站与两者差异较大。飞行探测试验表明:长航时复合翼无人机在近地面大气层探空方面机动性强,与常规旋翼无人机相比,可获取更大垂直与水平范围的气象要素信息。