面向虚拟装配的产品公差混合建模技术

为实现带公差的虚拟装配,应首先解决产品建模问题.通过分析虚拟装配对产品公差模型的要求,提出了虚拟环境下产品公差混合模型.该模型将产品基本公差信息与附加公差信息相结合,将普通几何拓扑信息与精确几何信息相关联,同时添加了装配特征等工程语义信息;详细阐述了产品公差混合模型的层次结构、模型信息来源、各个层次之间的映射方法及精度信息的表达方式;最后介绍了该模型的应用.     

MBD推起制造业信息化新浪潮（2）

MBD的理念要想达到其设计之初的目的，其实还有很多难关要克服。例如：设计的三维模型的模型尺寸往往都是最终精确尺寸，而我们知道在实际加工当中是有公差的。这些公差、粗糙度如果不能在三维模型上得到准确的反映，在未来的装配和实际使用中就会出现各种难于预测的问题，特别对于飞机、船舶这种大型工业产品，公差的累计效应会更加明显（多个零件的公差逐级累加，在最终装配时会产生难以控制的较大公差，无法达到设计精度）。     

尺寸公差模型

尺寸公差模型对产品信息的完备性和尺寸驱设计都是极为重要的。常见的尺寸公差模型是对传统工程图尺寸标注的实现，缺少设计过程方面的理论支持。文章还提出了特的特征的尺寸模式生约束模式的概念，给出了实例并讨论其应用。     

支持参数和公差设计的多学科协同建模

分析了多学科协同设计的耦合关系，提出支持参数和公差设计的多学科协同建模．首先。获得设计初始阶段各领域专家给出的约束条件和设计变量的大致范围；然后，抽取所有领域中在参数和公差设计阶段的耦合参数和相关约束；最后，构建产品的变动约束网络模型．在多学科协同建模中，考虑了不等式约束条件的转化、微分方程形式约束的转化、参数和公差的综合，以及与三维CAD系统的集成；为进一步实现参数和公差协同求解奠定了基础。     

详解Rhino修复模型破面

本文主要介绍如何使用Rhino协助修复模型的破面，使得模型的质量达到模具分模的要求，且能保证客户模型的形位公差需求。     

工程图公差和粗糙度向三维模型的映射技术

配合企业对基于MBD的产品设计和制造需求,为解决工程图与三维模型的标注映射问题,针对工程图中的形位公差和粗糙度,提出一种基于图匹配的工程图向三维CAD模型的标注映射算法.首先,基于DXF中性文件提取形位公差和粗糙度;然后,关联形位公差粗糙度和与之对应的工程图图元;建立三维模型投影所得的投影视图和工程图的空间关系图,对两个空间关系图进行图匹配;最后,获得工程图形位公差和粗糙度与三维CAD模型标注平面的关联.实验结果表明,该算法可以很好地实现工程图形位公差和粗糙度向三维CAD模型的标注映射.     

TRC磁头浮动块公差敏感性问题研究

采用数值法研究了ＴＰＣ磁头浮动块的公差敏感性问题。首先给出数值模拟公式，然后对一种ＴＰＣ磁头浮动块进行数值优化，研究此浮动块对加工工艺公差的敏感性。加工工艺公差主要包括台阶偏心公差、刻蚀深度公差、球冠面的Ｃｒｏｗｎ和Ｃａｍｂｅｒ。给出了影响浮动特性诸多参数的公差表，并对综合影响作了研究。     

SU-8胶微结构的尺寸公差研究

对SU-8胶微结构的尺寸及其公差进行了定量研究.在考虑了SU-8的吸收系数和折射系数对紫外光刻尺寸精度影响的基础上,根据菲涅耳衍射理论建立了紫外曝光改进模型和尺寸公差模型,对SU-8微结构的尺寸及其公差进行数值模拟.以硅为基底,进行了SU-8胶紫外光刻的实验研究.实验中掩模的特征宽度分别取50 μm、100μm、200μm和400 μm,SU-8胶表面的曝光剂量分别取400mJ/cm2和800mJ/cm2,测量了SU-8胶微结构的顶部线宽、底部线宽和SU-8胶的厚度,数值模拟结果与实验结果基本吻合.可以用本文的模型来预测SU-8微结构的尺寸及其公差.     

叶片模型公差约束条件下的配准方法研究

针对航空发动机叶片检测分析中的模型配准定位问题,结合叶片型面不同区域的设计公差要求不同的特点,以减少配准后超差点的数目为目标,提出了一种公差约束条件下的叶片模型配准方法。在迭代最近点匹配算法（Iterative Closest Point Algorithm,ICP）的基础上,根据公差要求定义约束区域,依据约束区域对点集进行加权处理,并给出了加权后的目标函数及其求解方法。通过实例验证了该方法是有效的,具有实用价值。     

基于SolidWorks 的尺寸公差参数化设计方法

随着企业快速响应市场的需要,参数化技术广泛应用于产品设计研发中。基于三维CAD系统的参数化技术主要考虑的是产品的基本尺寸设计,很少考虑尺寸公差,而尺寸公差又是产品的重要设计指标,所以为了解决尺寸公差参数化设计问题,对零件参数化模型中的尺寸公差信息表达、提取与标注方法进行了研究,提出了一种基于参数化技术的零件尺寸公差设计方法。利用VC＋＋,对三维CAD软件SolidWorks进行二次开发,开发出了基于SolidWorks的零件尺寸与尺寸公差集成参数化设计插件。以轴类零件为例,对提出的方法和开发的插件进行了应用验证。     

Composite web QoS with workflow conditional pathways using bounded sets

In our previous work (Dillon and Mansour 2009), a stochastic reliability model of atomic web services was proposed. Using the well-known classic two-state bounded set technique, we developed a service-oriented model that dynamically calculates the reliability of composite web services with rollback recovery (Mansour and Dillon in IEEE Trans Serv Comput 4(4), 2011). In order to improve the Quality of Service, fault tolerance techniques have been introduced using recovery block adaptation. Our workflow was based on series-parallel structures that constitute parts of existing structures. It is worth mentioning that major service-oriented systems contain larger and more complex structures than the simple series and parallel ones. This is a limitation in our previous approach. In order to consider more realistic service-oriented systems, other main structures, such as AND, XOR and Loop, should be included into our model. In this article, our previous structures are generalized to include AND, XOR and Loops. In addition to generalized structures, we extended the existing two-state bounded set technique to include three-state systems. This extension was especially motivated by XOR-based structures. A comparative study between bounded set techniques and a new stochastic model is also presented. Our simulation results accurately reflect the performance of the new proposed model and confirm our theoretical studies. Furthermore, Monte Carlos simulations were performed and the results obtained clearly validate our stochastic model.     

Neural associative memory for brain modeling and information retrieval

This work concisely reviews and unifies the analysis of different variants of neural associative networks consisting of binary neurons and synapses (Willshaw model). We compute storage capacity, fault tolerance, and retrieval efficiency and point out problems of the classical Willshaw model such as limited fault tolerance and restriction to logarithmically sparse random patterns. Then we suggest possible solutions employing spiking neurons, compression of the memory structures, and additional cell layers. Finally, we discuss from a technical perspective whether distributed neural associative memories have any practical advantage over localized storage, e.g., in compressed look-up tables.     

基于装配顺序的飞机装配容差信息建模

论文提出了基于装配顺序的装配容差信息建模方法,以装配仿真路径规划 的装配顺序为基础,提取装配体中各零件的特征约束关系及相关的关键特征,进而获取组成 环容差信息,建立装配容差信息模型。该模型考虑了装配顺序对装配误差累积过程的影响, 减少了人工容差信息建模繁琐的交互操作,提高了装配容差信息的建模质量。基于DELMIA 平台开发了飞机装配仿真系统。该系统已在工程上成功应用,提高了飞机装配仿真的效率, 减少了飞机实际装配生产中的出错率。     

保边缘自蛇模型毫米波图像去噪

由于毫米波图像分辨率低并伴随有大量噪声,其图像边缘常被噪声污染或丢失,为此提出保边缘自蛇模型并应用于毫米波图像去噪。引入只在图像的边缘处具有最大值,且对噪声不敏感的非局部梯度,以此构造边缘停止函数,使其在图像边缘处接近0,而在平坦同质区域接近1;给出保边缘的自蛇模型迎风差分数字解法;提出毫米波图像去噪的定量评价算法性能指标。实验结果表明,该算法在等效视数和边缘清晰度性能指标上明显优于标准自蛇模型和保特征的各向异性扩散模型,具有较好的去噪效果和保边缘能力。     

The route to a defect tolerant LUT through artificial evolution

Evolutionary techniques may be applied to search for specific structures or functions, as specified in the fitness function. This paper addresses the challenge of finding an appropriate fitness function when searching for generic rather than specific structures which, when combined wiacteristic of defect tolerance on the circuit. Production defects for integrated circuits are expected to increase considerably. To avoid a corresponding drop in yield, improved defect tolerance solutions are needed. In the case of Field Programmable Gate Arrays (FPGAs), the pre-designed gate array provides a bridge between production and the application designers. Thus, introduction of defect tolerant techniques to the FPGA itself could provide a defect free gate array to the application designer, despite production defects. The search for defect tolerance presented herein is directed at finding defect tolerant structures for an important building block of FPGAs: Look-Up Tables (LUTs). Two key approaches are presented: (1) applying evolved generic building blocks to a traditional LUT design and (2) evolving the LUT design directly. The results highlight the fact that evolved generic defect tolerant structures can contribute to highly reliable circuit designs at the expense of area usage. Further, they show that applying such a technique, rather than direct evolution, has benefits with respect to evolvability of larger circuits, again at the expense of area usage.     

容灾系统研究

随着IT系统的广泛深入应用,IT系统的高可用性和容灾能力问题日益成为一个关注的焦点,容灾系统的建设对于国防、政府、企业都有着重要的意义.容灾系统的目标在于提高IT系统的生存能力,保障业务流程的连续性,减少因各种灾难而造成的损失.该文依照工程化的思想,以容灾系统生命周期模型为基础,提出了容灾系统的需求分析和设计方法,并对主要的容灾技术进行了比较分析.     

An object-oriented system for tolerance charting

This paper presents a scheme to automate the entire process of tolerance charting. An object-oriented database called TOLCHAIN is developed to support this scheme. TOLCHAIN stores all the necessary information for tolerance charts to determine the intermediate machining tolerance values automatically. It is assumed that the part is stored as a boundary model. Feature volumes are then constructed from the boundary model to perform the tool accessibility analysis and to determine the process sequence. The intermediate machining tolerances are derived automatically from the boundary model.     

Multi-granulation rough sets based on tolerance relations

The original rough set model is primarily concerned with the approximations of sets described by a single equivalence relation on the universe. Some further investigations generalize the classical rough set model to rough set model based on a tolerance relation. From the granular computing point of view, the classical rough set theory is based on a single granulation. For some complicated issues, the classical rough set model was extended to multi-granulation rough set model (MGRS). This paper extends the single-granulation tolerance rough set model (SGTRS) to two types of multi-granulation tolerance rough set models (MGTRS). Some important properties of the two types of MGTRS are investigated. From the properties, it can be found that rough set model based on a single tolerance relation is a special instance of MGTRS. Moreover, the relationship and difference among SGTRS, the first type of MGTRS and the second type of MGTRS are discussed. Furthermore, several important measures are presented in two types of MGTRS, such as rough measure and quality of approximation. Several examples are considered to illustrate the two types of multi-granulation tolerance rough set models. The results from this research are both theoretically and practically meaningful for data reduction.