一种新的故障树定性分析方法

提出基于割序集的分析方法以研究故障树顶事件发生时基本事件的动态行为。利用顺序失效符表示事件的顺序失效关系,并将静态门和动态门转化为顺序失效表达式来描述故障树中各种门的动态行为,利用顺序失效表达式构建故障树的割序集。结合实例阐述故障树割序集生成算法的流程。该算法将失效行为表示为长度小于系统中部件个数的有序部件序列,为研究故障树提供了一种新的定性分析方法。     

基于DEMATEL的多电飞机起动发电系统部件失效关联性分析

针对多电飞机起动发电系统部件间的强电耦合关联关系,开展基于主要特征量变化和决策试验与评估实验室法(DEMATEL)的部件间失效耦合关系分析。建立了基于Modelica的多电飞机起动发电系统仿真模型,提出基于故障注入时系统主要特征量的变化,仿真研究系统不同失效的影响机理和不同部件间失效耦合程度,构建直接影响矩阵的方法。利用DEMATEL方法对直接影响矩阵进行解耦,解算部件失效影响的中心度和原因度等参数。对比故障树分析(FTA)结果表明,所提出的部件失效关联性分析方法正确合理,为复杂电子电气系统失效相关性分析方法提供了参考。     

元部件重要度分析的一种神经网络方法

1 引言在系统可靠性分析中,系统中各个元部件并不是同等重要的:有的元部件失效就会引起系统失效,有的则不然。一般认为,一个元部件或系统某一最小割集对系统的贡献度称之为重要度,它是系统结构、元部件的寿命分布及时间的函数。重要度分析在改进系统设计,确定系统需要监测的部位,制定系统故障诊断时的核对清单等工程设计中具有非常重要的作用。设计中往往要按重要度将元部件排序,对其中的关键元部件进行特别处理。     

面向软件错误定位与理解的测试执行离散特征筛选

软件错误定位与错误理解是软件调试过程中的重要步骤,然而调试人员利用基于覆盖分析的软件错误定位获取的可疑度,从高到低静态分析每条程序语句的检查方式,与实际软件调试过程并不相符。为了能够筛选更有助于理解错误根源的测试执行,尤其是致使程序失效的失效执行,帮助调试人员进行动态差异化分析,针对失效执行提出基于高可疑度覆盖率、揭示错误潜力和覆盖语句可疑度离散特征的3种优先级策略,针对成功执行提出加权余弦相似度匹配策略。通过将3种失效执行优先级策略与随机选择在常用错误定位技术中进行实验对比,验证了基于覆盖语句可疑度离散特征的失效执行筛选策略能够对筛选前后的错误理解工作量变化产生更强的积极影响和更弱的消极影响,并能够在相同工作量下理解更多的错误,进而更有助于将错误定位结果应用于错误根源的理解。     

动态环境下基于线特征的RGB-D视觉里程计

基于RGB-D的视觉SLAM(同时定位与建图)算法基本都假设环境是静态的,然而在实际环境中经常会出现动态物体,导致SLAM算法性能的下降.为此,本文提出一种基于线特征的RGB-D视觉里程计方法,通过计算直线特征的静态权重来剔除动态直线特征,并根据剩余的直线特征估计相机位姿.本文方法既可以减小动态物体的影响,又能避免点特征过少而导致的跟踪失效.公共数据集实验结果表明,与现有的基于ORB(orientedFAST and rotated BRIEF)点特征的方法相比,本文方法减小了动态环境下的跟踪误差约30%,提高了视觉里程计在动态环境下的精度和鲁棒性.     

基于通信感知任务划分的异构系统低功耗优化方法

针对由通用微处理器和专用加速部件构成的异构并行系统,提出结合通信感知的并行任务划分和动态电压频率调节技术的异构系统能耗优化方法,该方法旨在将并行任务图划分并映射在异构处理单元,在满足性能约束的条件下最小化系统能耗.在目前典型异构并行系统中,主处理器与加速部件大都通过系统总线连接,必然引入不可忽略的通信开销,因此通信感知的任务划分技术是该问题的关键.提出了基于整数线性规划的静态最优能耗优化方法和基于遗传算法的动态能耗优化方法.并通过一个典型科学计算应用验证了本文方法的有效性.     

基于DFTA的电牵引采煤机调高液压系统可靠性分析

MG950/1915型电牵引采煤机调高液压系统具有动态失效行为,用传统静态故障树法无法分析其可靠性.该文提出基于动态故障树的采煤机调高液压系统分析法,建立了油缸运动阻力大的动态故障树模型.首先求解动态故障树中不同子树的顶事件在不同时刻的发生概率,能得到整体动态故障树顶事件在不同时刻的发生概率.其次通过寻找顶事件发生概率最大的子树及子树中概率重要度最大的底事件,得到精过滤器和粗过滤器是采煤机调高液压系统的薄弱环节,为采煤机的优化设计提供了理论依据.     

在分布式入侵检测系统中应用Mobile Agent

该文针对目前的分布式入侵检测系统的特点与安全性进行了分析。提出了采用将MobileAgent机制引入入侵检测系统中解决其自身安全性的办法。利用MobileAgent的特性,将IDS的节点变成可移动的部件,解决了传统的分层入侵检测系统因为其部件均为静态部件存在着的单点失效的问题,提高了IDS系统的自身安全性。     

基于动态不确定度理论的多传感器系统传感器失效检测方法

基于一致性检验方法和动态不确定度理论,试提出一种对多传感器系统中传感器的失效进行有效检测的系统方法.本方法由于在仅有传感器测量数据而其不确定度未知的情况下即可对传感器失效做出判定,且实时性好,故十分适用于航天、遥感等传感器性能可能存在较大变化的应用场合.     

基于部件设计的可靠性研究

研究基于部件设计的可靠性问题,首先提出了一个基于部件设计的模型：如何抽象地描述一个部件？如何利用已存在的部件构造新的部件？如何在给定部件实现的情况下,静态地验证部件的正确性？然后讨论在部件实现不可知的情况下,如何利用包裹（ｓｒａｐｐｅｒ）技术和虚拟部件行为模式动态地检测并保证部件运行的正确性。     

对象系统的组合交互计算

对象系统的计算是一个开放的、动态并发交互的过程,由系统与外部环境的动态交互以及系统内部各组件间的协同工作来完成.对象系统的行为变化是系统内、外因有机统一的具体表征,因此不能把对象系统的静态组合构造和动态计算行为当作两个孤立的个体分而治之.从这个统一原则出发,研究了基于组合构造模型的对象系统的交互计算.组合构造模型设计将对象系统的主要计算特征纳入一个统一的抽象基调之中,通过定义基调上的一组关系,把对象系统的层次结构和内部协同工作有机地结合在一起.在此基础上,给出了一个区分动作类型的交互演算(S/R演算),描述了组合对象系统的动态行为和交互,较好地刻画出对象封装性、对象计算的事件驱动性、动态绑定以及对象系统内部的交互与并发等固有特征.     

Improved component mode synthesis and variants

This survey focuses on the two known model order reduction schemes being widely integrated in various commercial finite element packages, namely, the static and dynamic condensation methods. The advantages as well as the corresponding drawbacks have been extensively analyzed in several papers throughout the last decades. Based on combining the beneficial properties of the aforementioned methods, several alternative reduction methodologies are outlined in this paper, i.e., the generalized improved reduction system method, the generalized component mode synthesis and the improved component mode synthesis with its generalized version, which incorporate in a more efficient way the system’s inertia terms. Therefore, the associated error regarding higher frequency ranges of interest is better controlled. Basis of these methodologies is the so-called master and slave degrees of freedom partitioning, the right selection of which highly influences the reduced order model’s dynamics. The methods are tested and verified on a rather small three-dimensional bar structure and on the lever part of a turbocharger’s variable turbine geometry. Several reduced order models are generated by varying both the number of Craig–Bampton modes and the selection of the required master degrees of freedom. A comparison is conducted based on the modal criterion of the corresponding eigenvectors and the associated computation time required.     

基于UML的模具企业动态联盟框架设计

单个模具企业设计与生产能力不足问题的解决途径是建立动态联盟,而动态联盟建立过程的关键是系统模型.因此,采用UML统一建模语言设计了一个模具企业动态联盟框架模型.系统结构为分层结构;系统功能包括基本信息管理、加盟企业信息管理、生产信息管理、分析控制管理.系统的静态模型使用静态结构图、组件图和用例图描述,系统的动态模型使用序列图、活动图等描述,数据库模型使用类图描述,并给出了模具企业动态联盟各成员与市场机遇目标的依赖关系.     

自行火炮履带板多载荷疲劳寿命仿真

履带板的疲劳寿命是自行火炮维修保障体系中急缺的指标,但因测试动载荷和确定受力部位困难,至今无人尝试分析其疲劳寿命.测试动载荷是通过前人所建自行火炮行走系虚拟样机在虚拟路面上行驶实现的.通过重现仿真过程,观察履带板位置和载荷分量的幅值的对应情况,推断载荷分量的产生机理与履带板的受力部位.分析了履带板有限元多工况静应力分布.利用静应力结果和动载荷进行多载荷疲劳寿命仿真,找出了疲劳寿命薄弱位置,给出了疲劳寿命值.说明计算机仿真手段分析履带板的疲劳寿命,可以得到物理实验难以测试到的动载荷,避开繁琐的传统疲劳物理实验方法.最后提出了需进一步讨论的问题.     

回转窑烧成系统故障诊断方法研究

针对水泥烧成系统过程变量繁多、变量间静态关系耦合强等特点,采用因子分析方法建立静态过程监控模型.针对系统时序相关问题,结合经典动态主元分析DPCA方法和典型变量分析CVA方法,提出典型变量动态主元分析CVDPCA过程监控方法,有效解决了DPCA方法扩展后的数据矩阵维度大等不足之处.将算法用于水泥烧成系统故障检测,结果表...     

Virtual optimisation of car passenger seats: Simulation of static and dynamic effects on drivers’ seating comfort

The virtual investigation of static and dynamic effects on seating comfort requires the application of an adequate human model. An appropriate seat model considering static and dynamic properties of the structure, the foam and the trim is needed to perform an optimisation for a lower load level on the driver. The evaluation of the seating comfort must be divided into a static and a dynamic part. For the computation of the relevant physical quantities with the human model CASIMIR and a detailed seat model, the finite-element solver ABAQUS (ABAQUS Inc., http://www.abaqus.comwww.abaqus.com) is used.

To reflect a real driving situation, in the first step the human model is adapted to the right posture, which is given by the inclination of the cushion and the backrest. The seating process is then computed by the load due to gravity. The static comfort is mainly evaluated by the seat pressure distribution. Results such as the H-point and the meat-to-metal value can give additional important informations for the ergonomic and structural design of the seat. As the model reflects the nonlinear properties and the finite-element solver considers the effects out of finite displacements and contact, a good correlation with measurement is achieved.

The dynamic simulation is carried out by a unit excitation of the seat slides at the clamping points. To consider frequency-dependent properties of foam, structure and the human body, the computation uses an implicit solver. Therefore the model is linearised after the nonlinear static seating process.

Dynamic comfort is evaluated by the seat-transfer function. The presented numerical method leads to a good correlation with the measurements. Superposing the results with real excitation signals enables the estimation of the dynamic loads as muscle or intervertebral disc forces on the driver.

Altogether this method, in an early state of the development enables the user to optimise a car passenger seat structure due to the static and dynamic comforts. Considering boundary conditions as higher load amplitudes and accelerations, the advantages of virtual development can also be applied for construction vehicle seats.

Relevance to Industry

The present method allows the evaluation of static and dynamic comforts in a virtual phase of seat development. Besides the reduction of time and costs, the application of the simulation enables the testing of new materials and ways of construction with low investment.     

滑动数据窗口驱动的贝叶斯-高斯网络及其在非线性系统辨识中的应用

工业控制场合中,需要获取非线性被控对象的结构特性,而系统动态响应的数据直接从外部特征上反映了非线性系统结构关系.为了充分利用非线性动态系统响应过程中的数据,本文提出了一种基于滑动数据窗口 (sliding data window)的贝叶斯-高斯神经网络 (SW-BGNN)模型.该模型将数据融合于网络模型结构中,借助于贝叶斯推理和高斯假设,利用滑动窗口数据,实现非线性动态系统的辨识和预测.整个SW-BGNN本身需要确定的参数很少,因此运算的时间很短,适合于非线性动态系统的在线辨识.将SW-BGNN应用于几个非线性动态系统的辨识和预测,仿真试验结果表明了SW-BGNN模型的有效性.     

A behavioral type system and its application in Ptolemy II

Interface automata [deH01] have been introduced as an interface theory [deH01a] capable of functioning as a behavioral type system. Behavioral type systems describe dynamic properties of components and their compositions. Like traditional (data) type systems, behavioral type systems can be used to check compatibility of components. In this paper, we use interface automata to devise a behavioral type system for Ptolemy II, leveraging the contravariant and optimistic properties of interface automata to achieve behavioral subtyping and polymorphism. Ptolemy II is a software framework supporting concurrent component composition according to diverse models of computation. In this paper, we focus on representing the communication protocols used in component communication within the behavioral type system. In building this type system, we identify two key limitations in interface automata formalisms; we overcome these limitations with two extensions, transient states and projection automata. In addition to static type checking, we also propose to extend the use of interface automata to the on-line reflection of component states and to run-time type checking, which enable dynamic component creation, morphing application structure, and admission control. We discuss the trade-offs in the design of behavioral type systems.Received September 2002Accepted in revised form November 2003 by M. Broy, G. Lüttgen and M. Mendler     

A Compositional Behavioral Modeling Framework for Embedded System Design and Conformance Checking

We propose a framework based on a synchronous multi-clocked model of computation to support the inductive and compositional construction of scalable behavioral models of embedded systems engineered with de facto standard design and programming languages. Behavioral modeling is seen under the paradigm of type inference. The aim of the proposed type system is to capture the behavior of a system under design and to re-factor it by performing global optimizing and architecture-sensitive transformations on it. It allows to modularly express a wide spectrum of static and dynamic behavioral properties and automatically or manually scale the desired degree of abstraction of these properties for efficient verification. The type system is presented using a generic and language-independent static single assignment intermediate representation.     

Neural network methods for the modeling and control of welding processes

While welding processes are of great importance in manufacturing, their modeling and control is still subject of research. The highly nonlinear, strongly coupled, and multivariable nature of these processes renders the use of analytical tools practically impossible. In this article a novel approach is presented which employs networks of simple nonlinear units: a neural network. A widely used welding process, the Gas Tungsten Arc Welding is presented and the problem of its modeling and control is exhibited. A very brief introduction to neural networks is followed by presenting the experimental results for modeling the static and dynamic behavior of the process, as well as some practical recommendations regarding the use of the neural network techniques for controlling these processes.