On analytical evaluation of glint error reduction for frequency-hopping radars

Analytical techniques are presented for evaluating the glint error reduction of frequency-agile tracking radars employing discrete frequency-hopping (FH). The techniques can be used to compare the tracking accuracies obtained with different procedures for frequency selection. The cases of random, cyclic, and hybrid FH are worked out in detail. An illustration using a simple alpha-beta tracking filter indicates that the preferred type of frequency selection usually depends on the filter gains used in a specific application.<>     

Rank detector preprocessor for glint reduction in a tracking radar

A rank detector is used to detect instantaneous received power fades in a tracking radar. On detection of a fade, censorship of the angular position measurement is implemented in a Kalman tracking filter. It is shown that this technique can typically give a 15% angular tracking improvement on highly dynamic targets     

Feedback median filter for robust preprocessing of glint noise

Glint noise may arise in a target tracking system. The non-Gaussian behavior of glint noise can severely degrade the tracking performance. Measurement preprocessing at the front-end of the tracker is an effective method to reduce glint noise. The preprocessor proposed by Hewer, Martin, and Zeh (1987), which used the computationally intensive M-estimator, may not be suitable for practical implementation. An alternative method employing the median filter is studied here. The median filter is well known for its simplicity and robustness. However, the efficiency of the median filter can be seriously degraded if input samples are not identically distributed. This is what we may encounter in the tracking problem. A feedback median filter is then proposed to overcome this impediment without substantially increasing complexity. Simulations show that the new preprocessor can greatly improve tracking performance in the glint noise environment.     

Homotopy based optimal configuration space reduction for anytime robotic motion planning

Anytime sampling-based motion planning algorithms are widely used in practical applications due to limited real-time computing resources. The algorithm quickly finds feasible paths and incrementally improves them to the optimal ones. However, anytime sampling-based algorithms bring a paradox in convergence speed since finding a better path helps prune useless candidates but also introduces unrecognized useless candidates by sampling. Based on the words of homotopy classes, we propose a Homotopy class Informed Preprocessor (HIP) to break the paradox by providing extra information. By comparing the words of path candidates, HIP can reveal wasteful edges of the sampling-based graph before finding a better path. The experimental results obtained in many test scenarios show that HIP improves the convergence speed of anytime sampling-based algorithms.     

Packaging Requirements ents for Optimized Malfunction Isolation by Systematic Substitution

This paper describes a malfunction isolation technique which is applicable, primarily, to electronic systems. The technique is effective for essentially 100 percent of all failures, including multiple,terintermittent, interconnection, and closed-loop failures, to the discard-at-failure (DAF) hardware level. The value of the technique, in addition to its simplicity and ease of use, is that, in very complex systems, it virtually eliminates the requirement for complex procedures, high personnel skill levels, and manual test equipment necessary for malfunction ion isolation. The sine qua non of the technique is the packaging of the equipment. Each level of hardware must contain approximately four plug-in packages per package. Malfunction isolation is accomplished by substitution of packages in the top level, one at a time, until the defect is corrected. Next, the second-level packages in the defective top unit are replaced, one at a time, until the bad package at this level has been identified. The packages are substituted in each subsequent level until the DAF item is reached. When an equipment is packaged according to this technique, the average number of substitutions required to isolate to a single malfunctioned DAF item is approximately 1.8 times the natural logarithm of the number of DAF items in the system. For example, a system containing 4100 DAF items requires about 15 substitutions to locate a single defective item. The foregoing is true when no information is available regarding the best sequence of exchange. If such information is available, the number of substitutions will be reduced.     

未来海上空战对舰载战斗机的发展需求

针对未来海上空战的特点，通过美俄两国主要的舰载战斗机的对比分析，提出了几点对未来航母舰载战斗机的发展需求。     

Correlation analysis of PCB and comparison of test-analysis model reduction methods

The validity of correlation analysis between finite element model（FEM） and modal test data is strongly affected by three factors, i.e., quality of excitation and measurement points in modal test,FEM reduction methods, and correlation check techniques. A new criterion based on modified mode participation（MMP） for choosing the best excitation point is presented. Comparison between this new criterion and mode participation（MP） criterion is made by using Case 1 with a simple printed circuit board（PCB）. The result indicates that this new criterion produces better results. In Case 2, 35 measurement points are selected to perform modal test and correlation analysis while 9 selected in Case 3.System equivalent reduction expansion process（SEREP）, modal assurance criteria（MAC）, coordinate modal assurance criteria（CoMAC）, pseudo orthogonality check（POC） and coordinate orthogonality check（CORTHOG） are used to show the error introduced by modal test in Cases 2 and 3. Case 2 shows that additional errors which cannot be identified by using CoMAC can be found by using CORTHOG.In both Cases 2 and 3, Guyan reduction, improved reduced system（IRS） method, SEREP and Hybrid reduction are compared for accuracy and robustness. The results suggest that the quality of the reduction process is problem dependent. However, the IRS method is an improvement over the Guyan reduction, and the Hybrid reduction is an improvement over the SEREP reduction.     

国际上教练机的装备需求浅析

空军规模的大小对教练机装备的数量、类型、功能需求各有不同。本文通过对世界部分国家的空中力量、教练机装备以及飞行员训练情况进行梳理,分析不同规模下的空军对教练机的装备需求、发展需要,并从中得出几点发展思考。     

浅析机载软件工具鉴定要求

随着大量工具应用于机载软件的开发,工具鉴定的问题日益突出。本文介绍了机载软件工具鉴定的原因和目的,并基于机载软件工具的分类介绍了工具鉴定的前提和准则以及工具鉴定的数据要求,最后提出了工具鉴定过程中需要关注和解决的问题。     

反推力装置的安全性需求与经济性需求

现代运营的涡扇运输机一般都配装反推力装置,最初设计反推力装置是为了飞机能在短的跑道降落,从而降低机场建设长跑道的成本。反推力装置不是适航条款必须配备的装置。随着飞机刹车、减速板能力的增强和可靠性的提高,以及运营中反推力装置产生经济性收益不明显的实际情况,飞机供应商认为不安装反推力装置时飞机经济性更高,但航空公司则认为;反推力装置的首要需求是提高飞机减速功能的安全裕度,是一个安全性需求,特别碰到雨、雪和污染跑道、高高原机场和中断起飞等情况,反推力装置是目前飞机必不可少的减速装置。     

EM Transient Protection Requirements for Avionics LRUs

Avionics and electronic equipment installed in aircraft and air breathing missiles are required to operate without upset or damage when subjected to EM environments caused by lightning, NEMP, and Intrasystems transients. To simplify the design effort required to protect electronic equipment and minimize overlapping transient requirements and qualification tests, unified test requirements and procedures are needed. The goal of these unified test procedures would be to insure a known susceptibility level for each newly designed electronic Line Replaceable Unit (LRU). Ten avionics equipments in current Air Force inventory were tested for the purpose of developing unified procedure test methods. Operating LRUs were subjected to transients using common mode cable current (CMCC), groung potentials and chatteriing relay cable injection methods. Based on observed test results and review of current test requirements, test methods and test levels for unified test procedures for power-on transient tests of avionics equipment have been formulated.     

超视距攻击模式对机载武器火控系统的要求

未来空战的主流模式是超视距攻击,本文从提高作战效能出发,阐述了超视距空战的概念、战场环境、机载武器火控系统应具备的条件,强调发展基于超视距空战模式的机载武器火控系统的必要性。     

Overview of some optimal control methods adapted to expendable and reusable launch vehicle trajectories

Launcher trajectory optimization is a complex task, especially when considering the specific problems arising in the study of reusable launch vehicles. Part of the difficulty comes from the different characteristics of the trajectory arcs which make up the vehicle's mission (constraints and controls may not be the same). Another difficulty is the necessity, in some cases, of a global optimization between ascent and re-entry phases (branching optimisation). Finally, optimization tools devoted to this task should be polyvalent and robust, as the studies of reusable launch vehicles usually cover many different concepts, and also many different trajectory cases (such as abort scenarios). The purpose of this paper is to present different approaches used in France by CNES and ONERA to solve optimal control problems in the context of launcher trajectory optimization. These approaches, which are powerful implementations of classical optimization methods, were designed to cover the needs for both expendable and reusable launchers trajectory calculation. The first optimization tool presented is OPTAX, which uses an indirect shooting method. The second and third tools presented are CNES's ORAGE and ONERA's FLOP/OLGA, which use two different variants of the gradient method. The paper describes the equations and methodology behind these tools, and also presents their advantages and drawbacks.     

航母适配性的基本设计要求

从几何、结构、气动和机载子系统设备4个方面将舰载机与航母之间适配性的基本设计要求进行了论述,可为舰载机与航母之间协调设计提供参考。     

结构FEA建模通用要求标准的研究

介绍了结构FEA建模技术,分析与研究了结构FEA建模技术的应用及其标准化情况,提炼出了结构FEA建模过程应遵循的策略,归纳出了结构FEA建模的通用要求,给出了该领域内标准化工作的建议.     

Pointing and Stability Requirements for Earth Orbital Experiments

Experiments for manned and unmanned space facilities of the next decade will impose stringent requirements for accurately pointing and/or maintaining stability of the space platforms over extended periods. Potential experiment programs identified to date in various NASA-and contractor-sponsored studies have been reviewed in order to define critical values and ranges for the following pointing/stability parameters: 1) pointing accuracy, 2) line-of-sight stability, 3) angular rate, and/or 4) acceleration level. The most stringent requirements were found to be in the research categories of: stellar and solar astronomy, earth observations, space physics, communications and navigation, and space biology.     

RNP的运行标准和机队装备要求

所需导航性能(RNP)是今后航空导航领域的总体评定标准,为获得RNP的运行批准,合理利用RNP运行所带来的优势,运营人需要对机队进行合理的装备。     

民机材料适航要求与标准化需求

介绍了民机材料适航性要求及国内材料适航方面的差距,分析了航空材料标准现状和民机研制对材料标准化的需求,提出了今后民机材料标准化的工作重点。     

民用运输类飞机的高原适航性分析

高原机场和航线运行的特点 民用运输机的高原机场和航线运营问题,在全球范围内只有少数几个地区会涉及到.这些典型的地区包括:南美、中亚和中国.而中国的青藏高原无疑是所有这些地区中环境最为恶劣的地区.     

智能制造环境下的数控系统发展需求

"智能"是"中国制造2025"的核心要素,数控系统是制造装备实现智能化的关键要素。论文首先提出机床的信息互通和开放式标准数据接口是实现机床智能化的前提,举例说明了STEP-NC在通用数据接口方面的优越性,概述了适用于数控系统的通讯总线特征;在此基础上,介绍了工艺大数据对生产加工的重要性和其对新一代数控系统的要求,针对制造业数据平台的需求,对大数据信息挖掘技术做了相关介绍。依托于以上两点,总结了智能化数控系统可具备的功能,依托于工艺大数据平台,重点分析了智能工艺规划和加工参数自整定的实现方案,以及智能数控对高速高精加工所提供的便利。