高马赫飞行器迎风面与攻角对光学窗口周围流场的影响分析

为了提高高马赫飞行下光学窗口的光学性能,对比分析了基于气动光学效应三种飞行器模型不同攻角的马赫数场、密度场、温度场和压力场的流场结构及对光学性能的影响.首先, 根据飞行器与来流的迎风面,建立了三种飞行器典型模型;继而, 给出了0、5和10攻角飞行工况;然后,建立了基于Navier-Stokes方程和湍流模型的三种攻角流场分布;最后, 对比分析了宽平头体飞行器中三种攻角温度场作用下的光学系统传递函数.结果表明,马赫数场与密度场、温度场与压力场分别具有相似分布形式;相同飞行速度和攻角下,大迎风面的飞行器光学窗口周围温度与压力较小迎风面大;相同飞行器,较大攻角对应较大流场强度,攻角为0、5和10时传递函数分别为0.188,0.097和0.028.此分析结果可为高马赫飞行下光学窗口优化提供一定的理论依据.     

大攻角下基于信息融合的攻角/侧滑角估计方法

攻角和侧滑角是飞控系统和导航系统的重要参数。针对高性能飞行器在大攻角飞行时攻角和侧滑角不能精确测量问题,引入飞行动力学模型,选取姿态、姿态角速率、气流角和速度等飞行参数作为状态向量,以惯性导航系统提供的姿态、姿态角速率、加速度组成观测向量,构建扩展卡尔曼滤波器,融飞行动力学模型求解和状态估计的过程为一体,实现攻角和侧滑角实时精确估计。利用X-Plane系统的飞行仿真数据对攻角/侧滑角估计方法的可行性和有效性进行了验证。仿真结果表明,该方法不仅具有较高的精度、良好的稳定性和鲁棒性,而且可提高大气数据系统的测量范围和可靠性,能够有效地适用于大攻角飞行环境下攻角和侧滑角的测量。     

面向毫克级仿昆扑翼微飞行器的力-力矩传感器

毫克尺度微型仿生飞行器基于柔性高频翅拍运动的升力机制,具有柔性大变形、振动非线性、多自由度力-力矩耦合等特征,其有效升力/力矩范围处于mN/(μN·m)量级,通用力传感器较难准确测定力学参数,进而给微型仿生飞行器的设计与控制带来一定的困难。文章提出了一种面向微型扑翼飞行器的新型力-力矩传感器,它可以在固定约束条件下实现微飞行器高频扑翼运动产生的升力和力矩的测量,为扑翼飞行器控制力和力矩解耦研究提供精度较高的数据。该传感器采用对称式多悬臂梁柔顺机构将升力/力矩转化为微小形变,结合高带宽、高精度电容位移测量装置,可以采集高频振动条件下的微小升力/力矩。基于梁理论进行了传感器力学建模,并结合有限元仿真验证了原理的可行性。对被测对象微型仿生扑翼飞行器的主要测量参数范围开展结构与工艺设计,实验结果显示,该传感器的升力测量范围为-10~10mN,力矩测量范围为-20~20μN·m,特征频率为1kHz,升力和力矩的灵敏度分别为0.01mN和0.01μN·m,经验证,对整机重量在80~250mg、工作频率在1~200Hz范围的微型扑翼飞行器具有较强的适用性。     

几何修型对JSM模型失速特性的影响研究

在使用非结构网格求解器WiseCFD-UG软件对NASA第三届高升力会议JSM模型进行数值模拟研究的过程中,发现前缘缝翼与主机翼交接处的几何修型方式对失速特性的模拟结果有较大影响。针对切缝与不切缝这两种不同的几何修型方式,分别生成了同等规模的非结构网格。两套网格得到的计算结果表明:大攻角下不切缝的几何修型方式得到的压力分布及升力系数与实验值吻合的更好,能够更好的模拟低速构型的失速特性。     

基于Fluent的飞行器气动参数计算方法

课题采用湍流模型中的单方程模型,并借助于商业CFD软件Fluent,对某型号飞行器在给定攻角和马赫数下进行气动力仿真。首先,采用湍流模型中的单方程模型对飞行器的绕流流场进行数学建模;其次,用Gambit软件对飞行器的外形进行几何建模,并进行网格划分和边界条件设定;最后,在Fluent中进行相关参数设置和气动力数值计算及仿真,得出了该型号飞行器升力系数、阻力系数和俯仰力矩系以及飞行器表面的压力分布和来流速度分布,并对结果进行分析。该研究表明单方程模型能够很好地解决具有壁面限制的飞行器气动力数值计算问题。     

攻角对临近空间飞行器侧喷射流红外辐射特性影响数值模拟

临近空间飞行器侧喷射流干扰效应对目标红外辐射特性规律影响受到广泛关注。文中以典型锥柱裙飞行器为研究对象,预测飞行器典型飞行工况(20 km@5 Ma)不同攻角下的绕流场、侧喷流和壁面温度,结合窄谱带模型处理高温气体辐射物性参数,采用视在光线法求解辐射传输方程,分析攻角对侧喷流的复燃及目标在不同谱带和不同观测角度下红外辐射特性的影响。结果表明：随着攻角由负转正射流复燃程度降低,α=10°较α=-10°偏低176%;侧喷流在2.7μm和4.3μm两个特征峰值波段辐射显著,其他波段内目标辐射主要来源于本体;目标辐射强度在俯视观测角度下随攻角由负转正而减小,在侧视观测角度下攻角出现引起辐射强度降低,α=±10°较α=0°偏低6.8%。该研究可为临近空间飞行器侧喷射流相关的目标特性识别提供理论参考。     

大攻角导弹非线性动态自动驾驶仪研究

以设计大攻角导弹非线性动态自动驾驶仪为目的,基于大攻角非线性弹体动力学模型,按过载跟踪误差渐进收敛为目标,建立了应满足舵机偏角的非线性动态方程。结合舵机动力学模型,并按照动态逆原理得到了期望的控制律表达式,然后进行了控制律简化。分别仿真验证了小攻角、大攻角和弹体模型参数摄动条件下控制律的性能,并与传统方法进行了比较。结果表明,非线性动态控制方法的指令跟踪和抗模型参数摄动的鲁棒性均优于传统方法。     

宽角抛物方程的格林函数及其应用

基于分部傅立叶变换法,建立了宽角抛物方程在二维无界空间的格林函数.提出了计算宽角抛物方程初始场的格林函数法.在此基础上,用宽角抛物方程法计算了高斯电流源辐射在海平面上传播衰减情况,并与几何光学双射线模型以及格林函数本身的计算结果作了比较,验证了此格林函数的正确性,从而为建立求解抛物方程的新方法——辅助位函数法奠定了基础.     

髋关节角多模型贝叶斯动态估计

步态分析在健康监测等领域中有着广泛的应用,精确估计髋关节角是步态分析的前提.但是大腿运动的高度非线性和不确定性,以及微型传感器测量噪声的不稳定性等诸多因素,基于微型惯性传感器的髋关节角精确估计面临着巨大的挑战.该文提出利用混合动态贝叶斯网络、多运动模型和噪声模型对髋关节角的非线性变化和测量噪声的改变进行建模,然后基于穿戴在大腿上的微型加速度传感器获得的测量值,通过高斯粒子滤波算法估计髋关节角度.实验结果表明该方法能够有效提高髋关节角的估计精度.     

跨音速大攻角电视制导炸弹绕流流场数值分析

应用计算流体力学的理论方法,对某型电跨音速大攻角电视制导炸弹绕流流场及其空气动力特性展开数值分析。其中,控制方程为雷诺平均的可压缩Navier-Stokes方程,湍流模型采用标准k-ε两方程模型,数值格式为二阶迎风格式。利用Gambit2.2软件对电视制导炸弹及其绕流流场进行三维建模,使用Fluent6.2软件对电视制导炸弹在亚、跨、超音速以及不同攻角条件下的三维流场进行数值模拟,得到相应的压力分布图、温度分布图、马赫数分布图,以及电视制导炸弹的阻力系数曲线和升力系数曲线。分析绕流流场结构规律,为进一步的等离子体激励改善电视制导炸弹气动特性设计提供参考和依据。     

Design of a mechanism for biaxial rotation of a wing for a hovering vehicle

This paper presents a novel mechanism to actuate the wings of a hovering micro air vehicle (MAV). The mechanism uses a single actuator, but each wing can rotate about two orthogonal axes. The goal of this work is to design a light-weight compact mechanism that flaps the wings, inspired from the wing motion of hummingbird and hovering insects, to generate enough lift for the vehicle to hover. This paper explains in detail the proposed mechanism and its working prototypes. Also, the paper presents a dynamic simulation of the mechanism. The proposed dynamic simulation is used to predict the theoretical lift of the ornithopter. Further, the theoretical model is supported by actual experimental data collected from the prototype. The experimental data shows that the vehicle has the potential to develop enough lift to hover.     

Development of a Cyclogyro-Based Flying Robot With Variable Attack Angle Mechanisms

This paper presents an experimental study on the development of a cyclogyro-based flying robot with a new variable angle of attack mechanism. A cyclogyro is a flying machine supported in the air by power-driven rotors that rotate about a horizontal axis, like the paddle-wheels of a steamboat. Machines of this type have been designed by some companies but there has been no record of any successful flights. Our design starts with a new variable angle of attack mechanism with an eccentric (rotational) point in addition to a rotational point connecting to a motor. The main feature of the mechanism with the eccentric rotational point is the ability to change attack of angles in accordance with the wing positions (as determined by the rotational angles of the cyclogyro) without actuators. The design parameters (wing span, the number of wings, and eccentric distance) of the flying robot are determined through a series of experiments. Experimental results show that the cyclogyro-based flying robot with the new variable angle of attack mechanism is capable of generating sufficient lift force for flying.     

基于PVDF压电传感器的微型扑翼机升力特性研究

采用一种新型方法测量微型扑翼机升力变化特性.在微型扑翼机机翼表面布置一矩形聚偏氟乙烯(PVDF)压电薄膜作为传感器,根据PVDF输出信号判断微型扑翼机对应的升力变化,与传统扑翼机升力变化特性实验研究相比,该方法具有简单、快捷、准确等优势.同时该文研究了微型扑翼飞行器在水平放置及迎风状态时的升力特性曲线,探讨了扑翼频率、飞行速度及扑翼的迎角对扑翼飞行升力的影响.     

仿蜻蜓扑翼微飞行器研究现状

蜻蜓被认为是飞行行为简单且机动高效的昆虫之一,因此成为众多微型飞行器(Micro Air Vehicle, MAV)的仿生设计原型。蜻蜓优异的飞行特性与其翅特性密不可分。它不仅可承受飞行过程中的多种载荷,而且能保持高效飞行特性。总结了蜻蜓翅结构特性、飞行特性和仿蜻蜓扑翼MAV的研究现状及最新研究进展,并分别对蜻蜓翅的翅脉、翅膜、翅结、翅痣、褶皱结构,体液流动,材料特性,飞行机理以及红外探测应用进行了概述。同时针对仿生扑翼MAV的微型化需求,对未来研究方向进行了分析。     

Energetics-based design of small flapping-wing micro air vehicles

The energetics of a flapping-wing micro air vehicle (MAV) is analyzed with the objective of designing it. The salient features of this paper are as follows: 1) designing an energy storage mechanism in the air vehicle similar to an insect thorax that stores part of the kinetic energy of the wing as elastic potential energy during a flapping cycle; 2) inclusion of simplified aerodynamic wing models and inertia of the mechanism using rigid-body modeling techniques; 3) optimization of parameters of the energy storage mechanism using the dynamic models, so that energy input from the external actuators is minimized during a flapping cycle. A series of engineering prototypes based on these studies have been planned which will justify the use of these mathematical techniques.     

基于智能复合微结构的亚手掌尺度压电双驱扑翼微飞行器的研究

该文设计、制作和研究了一种亚手掌尺度的双驱扑翼微飞行器。飞行器主要采用多层平面材料的智能复合微结构（SCM）加工工艺进行加工。装配得到的样机整机质量为244 mg,翼展61 mm。对样机的压电驱动器性能进行了测试。测试结果表明,压电驱动器空载共振频率约为1 100 Hz,负载共振频率约为28 Hz;对样机进行了升力测试,得到样机的升力为 0.689 mN。     

Development of a small air vehicle based on aerodynamic model analysis in the tunnel tests

Tunnel tests play critical role to aerodynamics analysis, but few work has been done in this area for developing small air vehicles. This paper presents development of an electrically powered small air vehicle prototype based on aerodynamic analysis in wind tunnel and water tunnel tests. Firstly, two airframe models in triangle and square wing planforms, each with a wingspan of 100 mm, are analyzed with a small-scale low speed wind tunnel. The purpose of the wind tunnel test is to examine the practical characteristics such as lift and drag coefficients. The test in a water tunnel is further carried out to investigate the relationship between the vortex aerofoil design and turbulences created. In both wind tunnel and water tunnel tests, the airframe models, apparatus and the methodology are discussed, and the testing results show that the triangle wing aerofoil appears greater maximum lift coefficient and little occurrence of vortex and turbulences. Secondly, based on the verified wing planform in the tunnel tests, a small air vehicle prototype was designed and fabricated. The ground and onboard subsystems or components, such as flight control unit, vision system, and propulsion system etc., are studied. The materials and fabrication processes are also presented in the paper. Finally, the developed air vehicle prototype is successfully tested in the real flight.     

滑翔飞行器线性伪谱模型预测控制三维轨迹规划

对高升阻比滑翔飞行器,在线性伪谱模型预测控制基础上提出新的再入制导律,除了满足传统终端约束与路径约束,还能以特定航向角抵达终点。以高维多项式代理技术泛化升阻比,得到关于能量和攻角的表达式,攻角在线调节升阻比以增强规划能力。再入飞行分为下降段和滑翔段,下降段维持最大攻角和零倾侧角以限制热流率。滑翔段应用线性伪谱模型预测控制,用降阶动力学模型预测终端偏差,线性化模型获得误差传播方程。由于积分计算复杂,以高斯伪谱法获取控制量的修正值,修正攻角、倾侧角相关参数和两次倾侧反转的能量时刻消除终端偏差。方法简单易行,精度高,便于在线应用,仿真结果显示该方法能满足提出的规划需求。     

空战中角度对攻击优势影响研究

角度评估指数是传统空战优势评估的常用指数之一,对评估现代超视距空战仍然有重要意义.针对现代超视距空战的特点,提出了转向时间模型这一新的角度评估模型.通过空战机动转向过程建立起空战几何态势各因素间的关联.然后以转向时间模型分析典型的空战态势,并对模型完成简化.最终结合算例验证了转向时间模型的有效性.