Space debris mitigation measures applied to European launchers

In November 1986, more than 20 years ago, an H8 upper stage of Ariane 1 exploded in orbit nine months after the end of its mission. So as to avoid the generation of debris in low Earth orbit, a dedicated complementary development modified the design, introducing systematic passivation of the stage. Ever since this event, space debris mitigation has been a major concern for all launcher activities in Europe.After a short recall of the launchers currently operated by Arianespace as well as those currently developed by ESA with CNES, particularly for the safeguard authority, including the most promising future evolutions, the set of applicable regulations is described. These rules are fundamentally derived from the IADC Guidelines (hence the UNCOPUOS ones), translated into European Code of Conduct and in some more applicable Standards, such as the one prepared by ESA. The process of preparing ISO standards, mainly through the ECSS Working Group, is also described.Three major families can be identified: minimization of Mission Related Objects, Passivation of stages at the end of mission, and orbital protected zones including the so-called 25-year rule.The paper describes how European launchers do or will fulfill these applicable standards, quantifying the efficiency of the mitigation rules, and describing improvement actions currently under study.     

基于规则的航空发动机孔探图像诊断方法研究

针对军用航空发动机内部损伤频率高、诊断决策时间长的问题,运用基于规则的推理方法,结合案例推理,进行了航空发动机内部损伤维修决策的专家诊断研究,开发了基于孔探图像的航空发动机内部损伤维修决策专家系统。依据领域专家的经验,通过分析得到了对该型发动机的专家知识,并将其转换为if-then的知识规则存放于知识库中;利用图像处理方法,对损伤进行测量,得到损伤的尺寸参数;根据损伤尺寸,依据相应的知识规则,应用正向推理得到损伤的维修决策。运用多个航空发动机内部损伤实例验证了所开发的专家系统的有效性。     

考虑不同载荷顺序下应力损伤模糊性的Miner法则

针对传统Miner法则无法考虑载荷加载顺序的缺陷，应用模糊理论分析了不同载荷顺序下疲劳极限附近的应力对构件造成疲劳损伤的模糊性，使修正后的模糊Miner理论能够较好地反映出载荷加载顺序对疲劳寿命的影响。算例分析结果表明，该方法可使疲劳寿命的预测误差由原来的61．6％减小到21．7％。     

一种支持分层设计快速线网提取算法

本文介绍一种快速线网提取方法,该算法是采用图论中求无向图连通分量的方法实现的,取得较好的结果。     

飞机整体壁板广义槽分层识别方法及其实现算法(英文)

To automatically obtain a machining area in numerical control （NC） programming, a data model of generalized pocket is established by analyzing aircraft integral panel characteristics, and a feature recognition approach is proposed. First, by reference to the practical slice-machining process of an aircraft integral panel, both the part and the blank are sliced in the Z-axis direction; hence a feature profile is created according to the slicing planes and the contours are formed by the intersection of the slicing planes with the part and its blank. Second, the auxiliary features of the generalized pocket are also determined based on the face type and the position, to correct the profile of the pocket. Finally, the generalized pocket feature relationship tree is constructed by matching the vertical relationships among the features. Machining feature information produced by using this method can be directly used to calculate the cutter path. The validity and practicability of the method is verified by NC programming for aircraft panels.     

基于图谱指标的滚动轴承故障特征提取方法

为了更准确地提取滚动轴承振动信号的非线性故障特征,将图信号处理(GSP)引入机械故障诊断领域,提出了基于图谱指标的滚动轴承故障特征提取方法。该方法将滚动轴承的振动信号转化为路图信号后,提取多个图谱指标;用Fisher得分(FS)算法对图谱指标的敏感度进行排序,并选取若干个最敏感的图谱指标作为滚动轴承的故障特征参数;用K-均值聚类算法识别滚动轴承的不同故障。应用实例表明:当分别选取1~5个最优的图谱指标、时域指标和频域指标对不同轴承故障进行识别时,图谱指标均没有出现错误,而时域指标和频域指标都出现了不同数量的错误,因此,图谱指标对轴承故障的区分能力优于时域指标和频域指标。     

纹理能量模板若干性质的研究

从实验出发,对纹理能量模板存在的内在规律及其纹理区域变化所具有的特点进行了探讨,从中总结出了一些有用的性质,获得了满意的试验结果。     

基于FM—AM转换的伪码调相-载波调频复合引信信号的脉内特征提取研究

伪码调相和载波调频复合信号因具有好的距离、速度分辨率和测速测距精度，所以广泛应用在雷达和引信中。在电子对抗中为了实施欺骗性干扰，必须有效地提取复合信号的参数特征，为此本文研究了FM-AM转换时频分析的理论及其实现方法，并利用该方法对伪码调相-载波调频复合信号进行了脉内特征分析。具体包括伪码调相正弦载波信号、伪码调相复合正弦调频信号及伪码调相复合线性调频信号。仿真结果表明，在信噪比为5dB时，利用FM—AM转换时频分析技术，不但可以提取载波调频的特征信息，而且能够有效提取伪码的特征信息。     

一种基于角点提取的遥感影像地面控制点自适应匹配算法

提出基于特征角点的控制点自适应匹配算法：依据图像数据灰度特征自动确定相应阈值，从基准影像上提取控制点。采用动态模板进行不等距搜索，确定潜在目标控制点；构建三角网，利用等角变换判别目标控制点；构建仿射变换方程来筛选目标控制点。该算法无需设定灰度相关系数最大值阈值即可判别目标控制点。选取ASTER和TM两种成像差异显著的图像数据，对该算法进行试验，结果表明。该算法可以准确提取有价值的特征角点，具有较高的控制点识别精度和运算效率，具有较强的适应性和应用价值，较之传统匹配算法有明显优势。     

基于微小卫星的空间目标光学探测定位方法

为实现空间目标的天基光学观测,利用双星定位原理,采用仅测角的观测方式,结合最小二乘法建立了双星几何定位模型。考虑到星点提取作为光学定位算法中的重要一环将直接影响最终的定位精度,因而针对就星图处理部分,分析了星图的灰度特点,采用阈值分割法进行了去噪处理,选取了几种质心法对星点进行提取,利用真实星图对提取结果进行比较,选出了形心法和阈值质心法 2种较为可行的星点提取算法。通过仿真计算和蒙特卡洛误差分析结果可知,不考虑误差时,定位误差小于 10-5 m;考虑主要误差源时,定位误差小于 100 m;且姿态误差对定位方法的精度影响最大,数值上可以达到总误差的 0.9倍以上,速度误差的影响最小,只有总误差的 1/30,可以忽略;定位误差近似呈高斯分布且误差的大小与误差源近似呈线性关系。由此可见,文章所建立的定位算法可以对空间目标实现较为精确的定位。