Radio Controlled “3D Aerobatic Airplanes” as Basis for Fixed-Wing UAVs with VTOL Capability

There are fundamental performance compromises between rotary-wing and fixed-wing UAVs. The general solution to address this well-known problem is the design of a platform with some degree of reconfigurable airframes. For critical missions (civilian or military), it is imperative that mechanical complexity is kept to a minimum to help achieve mission success. This work proposes that the tried-and-true radio controlled (RC) aerobatic airplanes can be implemented as basis for fixed-wing UAVs having both speed and vertical takeoff and landing (VTOL) capabilities. These powerful and highly maneuverable airplanes have non-rotatable nacelles, yet capable of deep stall maneuvers. The power requirements for VTOL and level flight of an aerobatic RC airplane are evaluated and they are compared to those of a RC helicopter of similar flying weight. This work provides quantitative validation that commercially available RC aerobatic airplanes can serve as platform to build VTOL capable fixed-wing UAVs that are agile, cost effective, reliable and easy maintenance.

3D modeling of Unmanned Aerial Vehicles Tilt Photogrammetry

Unmanned Aerial Vehicles(UAV)tilt photogrammetry technology can quickly acquire image data in a short time.This technology has been widely used in all walks of life with the rapid development in recent years especially in the rapid acquisition of high-resolution remote sensing images,because of its advantages of high efficiency,reliability,low cost and high precision.Fully using the UAV tilt photogrammetry technology,the construction image progress can be observed by stages,and the construction site can be reasonably and optimally arranged through three-dimensional modeling to create a civilized,safe and tidy construction environment.

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.

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.

固定区域平滑技术在UAV传递对准精度评估中的应用研究

针对无人机(unmanned aerial vehicle,UAV)动态环境下的捷联惯性导航系统(strapdown inertial navigation system,SINS)传递对准是航测系统初始化过程中的重要工作,采用固定区域平滑技术对捷联惯导系统动态环境下的对准效果进行评估。分析了固定区域平滑方法,提出了量测信息与基准系统的选取标准并建立了传递对准精度评估模型。在理论分析基础上进行仿真与试验验证。结果表明,采用固定区域平滑可对无人机航测惯导系统传递对准进行准确评估。

倾转四旋翼UAV过渡状态下旋翼/机身气动干扰数值分析

通过数值模拟的方法对十字构型倾转四旋翼UAV在倾转过渡状态下前旋翼/机身/后旋翼间的气动干扰进行了计算与分析。分别建立了孤立前旋翼、前后旋翼、前旋翼-机身、前后旋翼-机身组合时的计算模型。在不同旋翼倾转角下,研究了以上组合模型对前旋翼、后旋翼以及机身的气动力和力矩的影响并分析了相互间的气动干扰情况,得出了前旋翼是整机气动干扰影响的主导因素,揭示了旋翼/机身间气动干扰形成的原因,为该构型旋翼布置与控制系统的设计提供参考。

四阶动力学建模和随机最优控制的UAV目标跟踪

现存大多数固定翼无人机(UAV)跟踪地面目标的方法需要一个或多个严格的假设,限制了实际应用,针对此问题,提出一种基于四阶动力学建模和随机最优控制的UAV跟踪方法。使用四阶动力学方程对UAV随机动态和目标进行初始化建模;通过一个适当的状态转换概率函数帮助UAV为每一个滚转动作画出蒙特卡罗样本;通过随机优化控制问题的解决确定最优控制反馈策略。仿真实验结果验证了该方法在实际应用中的有效性,与其他优秀方法相比,提出的方法的UAV仰角没有超出瞬时视场角(-152°~32°)的范围,目标没有逃离UAV的视线之外,而其他方法会使目标逃离UAV视线一次或两次。另外,能容忍的最高平稳风速最高达6 m/s,高于其他方法。

A modified consensus algorithm for multi-UAV formations based on pigeon-inspired optimization with a slow diving strategy

This paper considers the formation control problem for a group of unmanned aerial vehicles( UAVs)employing consensus with different optimizers. A group of UAVs can never accomplish difficult tasks without formation because if disordered they do not work any better than a single vehicle,and a single vehicle is limited by its undeveloped intelligence and insufficient load. Among the many formation methods,consensus has attracted much attention because of its effectiveness and simplicity. However,at the beginning of convergence,overshoot and oscillation are universal because of the limitation of communication and a lack of forecasting,which are inborn shortcomings of consensus. It is natural to modify this method with lots of optimizers. In order to reduce overshoot and smooth trajectories, this paper first adopted particle swarm optimization( PSO), then pigeon-inspired optimization( PIO) to modify the consensus. PSO is a very popular optimizer,while PIO is a new method,both work but still retain disadvantages such as residual oscillation. As a result,it was necessary to modify PIO,and a pigeon-inspired optimization with a slow diving strategy( SD-PIO) is proposed. Convergence analysis was performed on the SD-PIO based on the Banach fixed-point theorem and conditions sufficient for stability were achieved.Finally,a series of comparative simulations were conducted to verify the feasibility and effectiveness of the proposed approach.

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。

基于混合收敛导航向量场的三维航迹跟踪方法

针对传统导航向量场在固定翼无人机三维航迹跟踪过程中带来轨迹振荡的问题,提出了一种采用混合收敛策略且增益自适应的导航向量场构建方法,实现对无人机三维航迹的稳定跟踪。首先利用期望轨迹误差函数的海瑟矩阵建立导航向量场收敛方向的修正矩阵,提出了一类牛顿方向和梯度方向结合的混合收敛导航向量场,提高了飞行轨迹的平滑性;然后设计导航向量场收敛项增益调节策略,可根据误差变化趋势和局部的向量场变化剧烈程度,对收敛项增益进行自适应调节。仿真实验表明,提出的方法解决了传统导航向量场在飞行航迹收敛至期望轨迹附近时出现的轨迹振荡问题,在跟踪精度和收敛速度上更有优势。

倾转机翼旋翼无人机倾转过渡状态数值模拟

倾转机翼旋翼无人机相较于传统构型倾转旋翼机能够显著改善悬停状态旋翼尾迹对机翼的气动干扰影响,提高飞行效率。针对该构型无人机具有复杂非定常气动特性的连续倾转过渡过程,采用由经典的分离涡模拟方法(DES)改进得到的延迟分离涡模拟方法(DDES)对其进行流场气动干扰计算,倾转过渡过程中无人机前飞速度、旋翼桨距角、机身与固定翼迎角以及短舱倾转角都随时间动态变化。通过与无倾转机翼传统构型对比,分析了倾转过渡过程气动性能变化以及流场机理。仿真计算结果表明,倾转初始状态无人机受到旋翼下洗流影响较小,在30°短舱倾转角以前的倾转过程,由于倾转机翼段阻力增大,导致旋翼需用拉力增大。倾转机翼段在倾转过程中产生的分离涡与旋翼下洗流尾迹产生碰撞干扰,导致在机翼翼梢位置产生更大的尾迹干扰区域,并且对内侧固定翼翼梢产生下洗效果,降低了整机升力。

全驱动倾转四旋翼式飞枪的建模与控制

欠驱动的机/枪一体式四旋翼飞枪位置和姿态的控制存在耦合,无法实现带俯仰角的悬停射击,移动射击过程中火控策略复杂。设计了一种全驱动的倾转四旋翼无人机,并以此作为飞枪载体,在实现系统解耦的同时,简化了控制分配方法。首先通过牛顿欧拉法对系统进行数学建模,然后利用反步法设计控制器并证明系统稳定性,最后通过Simulink进行仿真实验。实验结果表明:本文设计的全驱动飞枪模型可实现位置和姿态的解耦控制,跟踪误差小,可满足飞枪悬停射击、移动射击的射击要求,适用于实时性要求高的飞/火控系统。

Control techniques of tilt rotor unmanned aerial vehicle systems： A review

The tilt rotor unmanned aerial vehicle（TRUAV） exhibits special application value due to its unique rotor structure. However, varying dynamics and aerodynamic interference caused by tiltable rotors are great technical challenges and key issues for TRUAV＇s high-powered flight controls, which have attracted the attention of many researchers. This paper outlines the concept of TRUAV and some typical TRUAV platforms while focusing on control techniques. TRUAV structural features, dynamics modeling, and flight control methods are discussed, and major challenges and corresponding developmental tendencies associated with TRUAV flight control are summarized.

面向交通事故现场三维实景建模的无人机航拍参数

在交通事故现场三维实景建模的图像采集过程中,针对无人机(UAV)航拍参数主要依靠人工经验设置,导致模型测量误差大、精度低的问题,提出一种无人机航拍关键参数自动计算方法。首先,确认单镜头无人机环绕事故现场航拍的关键参数为航拍高度、云台角度和拍摄间隔角,并分析其与成像范围、成像精度以及重叠度的数值关系;然后,构建无人机航拍关键参数计算模型,以给定事故现场场景、无人机技术参数、图像长宽比以及重叠度要求为输入,在事故现场处于有效成像范围且无成像盲区的前提下,以提高图像利用率保障模型精度和呈现效果为目标,自动计算得到航拍参数;最后,结合实例,应用该方法计算无人机航拍参数完成事故现场的图像采集,经测算,构建的事故现场三维实景模型的平均测量误差为1.72%,测量精度为3.54 cm,相较于人工经验法平均误差降低47.56%,精度提高48.40%。研究表明:该方法能实现交通事故现场三维实景建模的航拍参数自动计算,构建厘米级误差的三维实景模型,可提升无人机航拍的参数化和自动化水平。

Prediction of electric-powered fixed-wing UAV endurance

To overcome the problems encountered in predicting the endurance of electricpowered fixed-wing unmanned aerial vehicles(UAVs),which were stemmed from the dynamic changes in electric power system efficiency and battery discharge characteristics under different operating conditions,the required battery power model and battery discharge model were studied.The required battery power model was determined using an approximate model of electric power system efficiency based on wind tunnel testing and the self-adaptive penalty function.Furthermore,current correction and ambient temperature correction terms were proposed for the trained Kriging model representing the discharge characteristics under standard operation,and then the discharged capacity-terminal voltage model was established.Through numerical integration of this model with the required battery power model,the electric-powered fixed-wing UAV endurance prediction model was obtained.Laboratory tests indicated that the proposed endurance model could precisely calculate the battery discharge time and accurately describe the battery discharge process.The similarity of the theoretical and flight test results reflected the accuracy of the proposed endurance model as well as the importance of considering dynamic changes in power system efficiency in endurance calculations.The proposed endurance model meeting precision requirements can be used in practical engineering applications.

强风干扰下固定翼无人机“元飞行”气动建模研究

强风干扰下的复杂空气动力学给固定翼无人机的安全稳定飞行带来了严峻挑战。为提高强风干扰下固定翼无人机的环境适应能力,发展了一种创新的“元飞行”气动建模方法。不同于传统气流系下的气动建模,“元飞行”气动建模是一种元方法论建模技术,其采用易于测量的飞行器相对于地面坐标系的运动变量进行描述,通过隔离实际飞行中难以观测到的风干扰影响,基于高阶泰勒展开多元函数变量分解理论,构建仅与无人机自身特性相关、不同风况条件下通用的固定翼无人机空气动力共性基函数解析模型,结合在线辨识的风干扰系数函数,进而实现对飞行器飞行过程中气动力(矩)的预测。研究表明文章发展的“元飞行”气动模型可以良好地预测未知风况下固定翼无人机的气动力(矩),为实时空气动力学建模的实现奠定了良好基础。

基于倾斜摄影测量的无居民海岛现状勘定方法

为高效获取无居民海岛的基础测绘数据,本文采用免像控无人机倾斜摄影测量的方法对无居民海岛进行测绘。根据实验数据,得出免像控实景三维建模后,检查点平面位置最大误差为17.57 cm,中误差为13.83 cm;高程最大误差为-17.63 cm,中误差为11.54 cm,该结果满足1∶500比例尺数字线划图的相应精度要求。由此可见,免像控无人机倾斜摄影测量技术可在保证测量精度的前提下,在无居民海岛的基础测绘中发挥重要作用。

无人机倾斜摄影技术的精细化建模

随着计算机技术科学和地理信息技术的快速发展,城市精细化建模的需求不断增加,无人机倾斜摄影技术构建的实景三维(3D)模型拥有时效性高、模型覆盖范围广、模型真实化强等特点为城市快速精细化建设提供可能,但该技术在建模过程中存在数据冗余、模型变形、影像缺失等多种问题常常会影响建模效果,无法满足精细化的需求,本文以天际航DP-Modeler平台展开精细化的研究,探索精细化模型的构建方法,有效验证了基于实景3D模型重新构建模型,大幅提升了城市精细化建模的效率,为精细化建模提供了切实可行的解决办法和技术支持。

无人机电力线路巡视平台选型

近年来随着电网规模的扩大和电压等级的提高,电力线路人工巡视已经越来越不能满足电网安全稳定运行的要求。无人机技术的不断发展,给巡视工作提供了新的平台和视角,是常规人工巡视的发展和有益补充。简述了无人机的发展历史和现状,对无人机进行了分类和对比,结合电力线路巡视的特殊性,阐述了用于输电线路巡视的无人机平台的性能要求,给出了选型建议,为无人机电力线路巡视工作的开展提供了参考。

利用固定翼无人机监测松材线虫病疫点枯死松树的初步研究

无人机航摄监测森林病虫害是一个新的研究热点。为探究无人机航摄在松材线虫病监测中的应用,本研究于2017年11月利用小型固定翼无人机采集了广东省河源市新丰江库区松材线虫病疫点的航摄影像,总面积1425.9 hm^2。固定翼无人机搭载了1台可见光数码相机和1台多光谱数码相机,能同时采集枯死松树的可见光和近红外的航摄影像。利用LAMapper软件对航摄图像进行空中三角测量和像素匹配,获得可见光正射影像和多光谱正射影像。使用ERDAS软件生成影像的归一化植被指数(NDVI)。然后将带有地理信息的完整影像自动导入GIS系统进行异常点识别和几何矫正,导出最终的影像数据。最后,对影像进行分析,并根据植被指数(NDVI)对图像进行分类。分析结果显示,航摄的疫点中共自动识别1486株枯死松树,并获得了其分布地图及坐标点位置。验证结果表明监测的准确率达到80%以上,坐标点精度达到2-3 m。本研究结果具有低成本、自动化、可靠、客观、高效和及时等优点,可为大面积监测松材线虫病的发生现状和流行动态、评估防控效果和灾害损失提供技术支撑。