集成LSTM的航天器遥测数据异常检测方法

航天器作为一类集合结构、热控、电源、姿轨控等的复杂系统,遥测数据是地面判断其在轨性能的唯一依据,而有效的异常检测是保证航天器在轨可靠运行的基础要素。针对遥测数据连续、离散样本混合且样本变化高度关联于指令的数据异常检测问题,提出一种基于集成长短期记忆网络(LSTM)的航天器遥测数据异常检测方法。利用LSTM强大的非线性建模能力,结合矩阵范数实现对遥控指令的多模式挖掘,并通过多LSTM预测模型的构建以及有效集成,提升模型对于航天器复杂工况的适应性,进而有效标记遥测数据中的异常。通过对NASA公布的2个类型航天器的遥测数据进行实验验证,结果表明,与基于LSTM的遥测数据异常检测方法相比,所提出的方法异常检测率提升明显,尤其适合检测上下文类型异常。测试结果验证了方法的可行性,可为航天器地面运控提供有效的数据判读能力。     

基于耦合自适应距离的高维异常检测算法

距离聚类方法是航天器等复杂系统实现遥测参数异常检测的常用方法之一,但在面对高维遥测数据进行异常检测任务时,往往会暴露出效率低下、精度劣化等严重问题。针对基于高维遥测数据的航天器异常检测难题,提出了一种基于耦合自适应的改进距离定义,并针对归纳监视系统(IMS)算法这一经典距离聚类算法进行了改进。该方法利用历史数据的分布特征,在进行聚类的同时,对于参数耦合性进行动态挖掘,并将挖掘到的知识高效地投入到异常检测任务。最后,采用运载火箭电源系统的真实高维遥测数据对所提方法进行了应用验证。在与多种传统基于IMS的异常检测方法的对比实验中,该改进算法检测效率与准确率较另两类IMS算法中的最优方法分别提升了41.83%和69.03%,验证了运用该距离定义的检测方法在效率与精确率上的优越性。     

基于对比序列重构的卫星遥测数据异常检测方法

基于遥测数据的异常检测是卫星在轨运维管理的关键技术。 但现有方法大多仅采用正常样本建立模型,异常检测结果 对判读阈值敏感、虚警率较高。 对此本文提出基于对比序列重构的卫星遥测数据异常检测方法,充分利用有限异常先验增强异 常检测中正常、异常样本差异。 先基于变分自编码器提取遥测数据时序演化特征,引入对比学习方法建立对异常、正常数据差 异化输出的编码器,再用大量正常数据进一步训练整个模型实现对正常数据的精准重构形成对异常数据敏感的时序数据重构 模型,再基于核密度估计方法学习异常判读阈值进一步提升异常检出率。 在真实卫星遥测数据上验证表明所提方法能有效降 低异常检测的虚警率(均低于 0. 002)并保持较高的检出率具备良好的实际应用水平。     

基于遥测数据相关性的航天器异常检测

基于信息技术进行星载设备的异常检测始终是空间任务安全性、可靠性领域最重要的主题。传统航天器异常检测方法的知识和模型很难自动化构建,而纯数据驱动方法会忽略系统设计知识和遥测数据本身的特性,造成先验知识的浪费。针对这些问题,提出一种基于遥测数据相关性的航天器异常检测方法。首先,给出遥测数据相关性的定义,结合量子卫星任务实例,对单维度遥测数据的6种领域相关性进行建模和向量表示;随后,提出一种遥测数据驱动进行相关性知识发现、进而将知识应用于异常检测的方法;最后,利用量子卫星数据、基于真实故障特征的模拟数据对该方法进行了验证。实验与分析结果表明:该方法能够实现航天器异常检测知识构建的自动化,且可以有效检测出遥测数据的异常。     

基于集成极限学习机的卫星大数据分析

卫星遥测大数据是卫星地面站判断其运行状态的唯一依据,遥测参数的有效判读对监测在轨卫星健康状态具有重要意义。而遥测数据维度高、数据量大、专业性强的特点为高精度、低误检率的多维遥测数据判读带来严峻挑战。因此,提出了一种基于数据驱动的卫星遥测大数据智能判读方法。该方法以极限学习机(ELM)预测模型为基础,对目标参数进行高精度的单步预测,同时,基于目标参数在时间维度上的变化趋势对预测结果进行修正。最后,基于集成学习的方法针对目标参数的不同类别分别给出判读策略。利用卫星电源子系统仿真数据和真实卫星遥测数据对所提出的参数判读方法的有效性进行验证,实验表明,该方法对不同类型的监测数据具有较强的自适应能力和鲁棒性。     

基于注意力残差网络的航天器测控系统故障诊断

随着航天器数量的不断增加,快速而准确地对航天器测控系统进行故障诊断尤为重要。针对航天器所处空间环境变化较大、遥测数据成分复杂和故障诊断准确率不高的问题,提出了一种基于注意力残差网络(AM-ResNet)的航天器测控系统故障诊断方法。首先,将原始遥测数据转换成灰度图像;其次,将图像依次通过残差网络和注意力模块,获取具有全局依赖关系的特征图;最后经过卷积、池化操作后利用Softmax分类器进行分类,实现航天器测控系统的故障诊断。实验结果表明,所提出的基于注意力残差网络的航天器测控系统故障诊断方法可将诊断准确率提升至95.68%,与ResNet-18、AlexNet和LeNet-5故障诊断模型相比,诊断准确率分别提高了3.53%、5.62%和16.43%,验证了该方法可以有效提高航天器测控系统故障诊断性能。     

基于数字孪生的航天器系统工程模型与实现

为践行智能制造、推进航天工业化与信息化深度融合,提出了基于数字孪生的航天器系统工程。分析了数字孪生技术的相关研究成果,从7个维度对航天器系统工程进行综合,建立了基于数字孪生的航天器系统工程整体模型和应用框架,并按照生命周期进展演化为设计、工艺、制造/装配、试验/测试与在轨运行5个典型阶段模型和应用框架。在技术实现层面,基于物联网、大数据、用于过程控制的对象连接与嵌入统一架构、系统建模语言、基于模型的定义、面向服务的架构等先进技术,构建了由物理空间、传输层、数据层、模型层、服务层和应用层构成的数字孪生系统架构。基于数字孪生的航天器系统工程能够有效实现航天器研制全生命周期信息世界与物理世界的双向动态实时交互共融与协同,从而推进航天工业智能制造的发展。     

基于约简边界样本界面检测器的设备异常度检测方法

针对在无故障样本情况下如何快速检测设备异常度问题,在约简自己空间边界样本数量的基础上,提出一种约简边界样本界面检测器。以Iris数据集为例进行分析,发现与已有的异常检测方法相比,约简边界样本界面检测器是一种具有高检测率高误报警率的异常检测方法,而且具有很强的数据压缩功能,尤其是在区分有较清晰类边界数据时,具有更好的检测性能。利用约简边界样本界面检测器异常检测方法分析轴承状态数据,不仅能反映出轴承的各种状态,而且能通过设备的异常程度反映出同类故障的轻重程度。约简边界样本界面检测器的设备异常度检测方法,是在学习设备正常运行数据的基础上,找到自己空间的边界样本,并根据一定规则将其约简后,结合其方位信息与训练样本半径,进行设备状态检测,不需要设备运行的故障数据,它适合对故障数据缺乏的设备进行有效的异常检测。     

气体传感器在国外航天器上的应用

气体传感器技术是航天器上获取环境气体信息的重要手段之一,对航天器的安全发射、宇航员的生存安全以及航天器在轨运行期间的安全具有重要的意义。对国外航天器气体传感器技术的发展概况和相关气体传感器成功应用的案例进行调研,分析总结国外气体传感器技术在航天器上的发展特点和趋势,为我国航天器气体传感器发展提供了一定参考。     

航天器太阳电池阵热-结构分析研究进展

太阳电池阵作为航天器的主要附件,在轨运行期间经历冷热交变的复杂热环境,在结构内部产生随时间变化的温度梯度,导致结构的热变形和热致振动,对航天器的正常运行产生重要影响。文中从航天器在轨运行空间热环境分析出发,综述了太阳电池阵的热分析、结构单元热-结构分析和热稳定性分析的研究进展,探讨了太阳电池阵热-结构分析的未来发展方向。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.