基于数字地图预处理的低空突防航迹规划

为保证飞行器能够实现所规划的航迹,研究了将地形及飞行器性能等信息融合构造虚拟地形表面的数字地图预处理方法,包括数据插值具体步骤和地形平滑处理方法。通过设计综合地形跟随、地形回避、威胁回避(TF/TA2)的目标函数,对最小威胁曲面进行转化,提高了实时航迹规划的速度,采用微分进化(DE)优化算法,实现了三维TF/TA2最优实时航迹规划。仿真结果表明,此地图预处理和实时航迹规划算法是有效可行的。     

无人飞行器航迹规划方法综述

首先从不同角度给出航迹规划的两种定义,把航迹规划问题拆分为规划空间、航迹表示、约束条件、目标函数、规划算法五个子问题,提出了适用于各类无人飞行器航迹规划问题分析求解的过程模型。对规划空间构造方法、目标函数、规划算法进行分类比较,并给出每种方法的优、缺点及适用范围,辅助规划人员针对具体需求快速明确规划思路并选择算法。最后指出了航迹规划未来面临的新问题、新挑战。     

无人机航迹规划算法

无人机是现代战场实施侦察、打击的有力武器,它的发展备受关注。无人机航迹规划源于机器人运动规划,它是无人机应用研究的核心内容,对提高无人机系统在复杂战场的作战能力起着关键作用。无人机战场环境日益复杂,在强拒止、强电磁环境下,航迹规划对自主性和智能化有更高的要求,传统单一约束的算法已不能满足现今的战场需求。文章系统梳理了 5类无人机航迹规划算法中的几种常用算法及其改进算法,归纳了这些算法的原理、优缺点及适用条件,指出现阶段存在的问题与无人机航迹规划算法面临的挑战。综述表明,航迹规划算法必然向着智能化发展,自主识别和智能决策是改进、优化算法的关键。     

突防飞行与多区域搜索一体化侦察航迹规划

针对战场环境下无人机的侦察路径规划问题，首先设计突防飞行与多目标区域搜索的一体化侦察航迹规划策略。然后针对侦察任务中的突防问题，在传统快速扩展随机树(RRT)的改进算法基础上，提出一种基于改进RRT^*的无人机突防航迹规划方法，通过设计目标偏置算法解决了传统RRT算法采样点随机性大、收敛速度慢等问题。针对侦察任务中的目标搜索问题，使用改进的旋转卡壳路径规划器(RCPP)进行覆盖式航迹规划，提高了搜索覆盖率。最终通过对比仿真试验，验证了所提出算法的优越性，以及算法应用于战场侦察任务的有效性。     

无人机航迹规划技术研究及发展趋势

通过对无人机航迹规划的研究,构建了无人机航迹规划的结构框架;分析了无人机系统约束及威胁场约束,探讨了无人机航迹几何建模方法及规划算法的国内外研究概况;并着重分析了规划算法。最后,阐述了无人机航迹规划面临的关键问题及发展趋势。     

基于改进A*算法的UUV冰下避障航迹规划算法

针对冰下避障航迹规划问题,提出了一种基于改进A*算法的三维冰下避障航迹规划算法.不同于传统的A*航迹规划算法,该算法结合了人工势场航迹规划算法的思想,将水下地形碰撞约束、海冰碰撞约束以及UUV巡航高度约束重新编排.算法分析表明,该避障航迹规划算法能够有效增强UUV冰下避障能力与定深巡航高度控制能力.基于改进的A*冰下避障航迹规划算法,给出了上述约束的设计方法并进行了仿真验证.仿真结果表明,基于上述约束的航迹规划算法具有良好的避障能力、巡航高度控制能力以及航行距离控制能力.     

用于无人机三维航迹规划改进连接型快速扩展随机树算法

无人机的广泛应用,使得航迹规划成为研究的热点。很多算法由于模型简单或规划方法低效,难以有效应用于复杂条件下的航迹规划问题,从而提出一种求解该问题的改进连接型双向快速扩展随机树(RRTConnect)算法。首先,建立无人机航迹规划问题的数学模型;然后,采用RRT-Connect算法求解上述模型时,提出六种生成随机节点的改进策略;最后,将改进的RRT-Connect算法应用于有雷暴威胁的无人机三维航迹规划问题,并与已有的RRT算法和RRT-Connect算法进行对比。结果表明:采用本文提出的方法能够高效的生成可行的无人机航迹。     

飞行器航迹规划算法综述

首先给出了飞行器航迹规划的概念和问题描述对航迹规划算法中的轨迹优化、路径规划和基于类比的航迹规划进行了分类介绍，其次对多飞行器编队航迹规划的两种控制方式进行了简单说明．最后指出了航迹规划中需要进一步研究的问题。     

军用飞行器航迹规划综述

介绍了军用飞行器航迹规划的基本概念，航迹规划与任务规划的关系，国内外研究现状，存在的问题，论述了航迹规划的基本要求，如导航要求，突防要求，飞行器性能要求及战略和战术要求，最后分析了航迹规划需要解决的威胁建模，航迹规划算法和轨迹跟踪控制等关键技术。     

基于一种混合算法的巡航导弹参考航迹规划

通过分析A*算法,提出了适合与遗传算法(GA)进行混合的改进方案,针对遗传算法求解巡航导弹参考航迹规划问题,讨论了在初始群体构建和变异操作中引入改进A*算法的混合方法,从而得到参考航迹.仿真结果表明,该方法具有很强的快速规划能力,并能得到较优的结果,适合于大规模复杂环境中的参考航迹规划.     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.