制造系统动态可靠性建模理论及其应用

在分析传统可靠性设计理论存在缺陷及面临挑战的基础上，评述动态可靠性建模主要方法。利用Petri网对动态系统的描述能力，将Petri网应用于系统故障分析和动态可靠性计算中，提出了基于故障Petri网的动态可靠性建模方法。以某挖掘机液压系统为例，研究了制造系统故障的Petri网静态描述和动态可靠性计算方法，求解得到系统可靠性数值指标。应用表明，随机Petri网在故障传播描述以及系统动态可靠性分析方面具有优势.     

供料机械臂液压系统动态可靠性研究

弹药自动装填技术已经成为现代火炮技术的一个重要分支,液压系统的可靠性是保证整机工作可靠的关键因素。主要分析了该装填系统中液压系统的动态可靠性问题,利用随机Petri网(SPN)建立了该系统的可靠性模型,并在PIPE软件中算出关联矩阵,求得最小割集,根据已知的各元件的失效率和维修率,算出动态可靠性,该方法为定量计算系统动态可靠性提供了参考依据。     

基于改进模糊故障Petri网的复杂系统故障诊断与状态评价EI北大核心CSCD

为提高复杂系统的可靠性,在综合模糊Petri网和故障Petri网优点的基础上,提出了改进模糊故障Petri网的建模及推理方法。该模型定义了库所、托肯及变迁的着色规则,并结合模糊产生式理论,应用于复杂系统的故障推理,从而更加直观、明确地描述故障状态及信息。该模型的正向推理反映了故障传播的固有特性,采用基于智能点火判断矩阵的正向演绎算法,实现了故障状态快速、准确的智能评价。该模型的逆向推理为故障诊断过程,引入智能的逆向推理矩阵,并结合基于Petri网关联矩阵的最小割集诊断法,实现了模型中任意库所故障的逆向自动诊断,同时根据故障易发率得出最小割集优先顺序,提高故障诊断的效率。以数控机床进给系统的故障分析为例,验证了所提模型和方法的正确性与高效性。     

基于随机故障Petri网的液压系统可靠性建模与分析

文章针对复杂系统动态可靠性建模的困难，利用Petri网对动态系统的描述能力，将Petri网应用于系统动态可靠性分析领域。基于模块化思想，提出随机故障Petri网的动态可靠性建模方法，有机地集成了二元决策图算法与马尔可夫过程理论的优点。通过液压系统实例验证了该方法的有效性。     

基于Petri网的机动车故障诊断专家系统设计

鉴于传统机动车故障诊断过程的复杂性、低效率和对维修人员素质的高要求,设计了一种基于Petri网的机动车故障诊断专家系统。该系统融合了多渠道故障特征的信息库和专家诊断知识库系统,在对机动车故障诊断过程中,系统先进行故障树分析(FTA),再利用Petri网的关联矩阵求出所有最小割集,并把它们作为诊断规则存入专家知识库;再结合最小割集重要度优先级来推理,实现机动车故障的快速定位并给出故障维修方案。最后用实例验证了该系统的实用性。     

基于Petri网的液压马达故障诊断

针对液压马达故障诊断中特征提取的瓶颈问题,提出一种基于Petri网的液压马达故障诊断方法。以叶片式液压马达为例,分析液压马达常见的故障及原因,利用Petri网的知识表示方法提取故障征兆和故障原因,建立基于petri网的液压马达故障诊断模型,经过Petri推理,结果表明该方法是有效的。     

基于Petri网的复杂制造系统故障树分析

针对动态复杂制造系统故障诊断问题,提出了一种融合Petri网与故障树的系统故障建模方法.基于对偶和再吸收原则来简化Petri网模型,应用库所矩阵法对处理后的简单模型求其最小割集;基于Petri网优化建模的结果,运用OpenFTA故障树分析软件对其进行定量分析,求得各最小割集概率重要度,顶事件发生概率以及各底事件概率重要度.该模型在不锈钢方坯连铸机结晶器故障应用结果表明,与通常的故障树求解方法相比,对于复杂的故障树,用该集成模型可有效地进行故障树的定性、定量分析,节省计算时间成本,提高分析效率,并提高了故障诊断的正确性.     

基于多源信息融合故障树与模糊Petri网的复杂系统故障诊断方法

针对复杂系统故障树模型构建困难且模型冗余节点多、计算复杂的问题,提出一种基于多源信息融合故障树与模糊Petri网的故障诊断方法。该方法先将多源信息进行标准化处理,从处理后的信息中提取维修元数据,同时利用数据挖掘方法得到故障关联项集。通过维修元数据、故障关联项集和系统结构关系的映射、融合,更加全面、准确地构建复杂系统故障树模型。采用模糊Petri网对多源信息融合故障树模型进行简化和改进,并利用基于模糊Petri网的动态故障推理方法和基于关联矩阵的最小割集求解方法建立复杂系统故障诊断方法,提高了故障的诊断速度与推理效率。以汽车发动机故障诊断过程为例,证明了所提方法的合理性和有效性。     

基于模糊Petri网融合推理的装备故障诊断技术研究

研究了模糊Petri网应用于故障诊断中的正向推理方法,针对某型工程装备液压系统故障的特点,建立了基于模糊Petri网的故障诊断推理模型,并以液压系统压力不足故障为例,探讨了正向推理方法在系统级故障诊断中的应用。实现了故障征兆的信息融合,该推理方法适用于现场的快速故障诊断。     

基于模糊Petri网融合推理的装备故障诊断技术研究

研究了模糊Petri网应用于故障诊断中的正向推理方法,针对某型工程装备液压系统故障的特点,建立了基于模糊Petri网的故障诊断推理模型,并以液压系统压力不足故障为例,探讨了正向推理方法在系统级故障诊断中的应用。实现了故障征兆的信息融合,该推理方法适用于现场的快速故障诊断。     

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.     

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....     

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。     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.