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。     

发动机数字化设计三维标注的几个关键技术

正MBD模型是最先进的设计信息传递模式。为了充分利用三维模型所具备的表现力,去探索便于用户理解、更具效率的设计信息表达方式,着重对发动机数字化设计三维模型标注所涉及的若干关键技术进行了论述与分析,包括三维模型标注的基本原则和特点,发动机三维模型的视图、尺寸、公差、技术要求及标题栏标注等,提出了相应的解决问题思路和技术手段。     

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.     

在AutoCAD2000中实现尺寸公差编辑功能

一、引言 AutoCAD2000是目前应用最为广泛的二维CAD软件,使用该软件进行机械产品设计时,将频繁地使用尺寸公差标注。与先前版本相比,虽然AutoCAD2000在此方面已有较大的改进(使用设置标注样式来实现各种形式的尺寸公差标注),但其设置过程过于繁琐。如果能利用AutoCAD2000提供的二次开发工具,通过编程开发出一个尺寸公差编辑模块。这样在绘图过程中,用户可以先直接使用AutoCAD2000提供的各种标注命令标注出无公差的尺寸,然后再逐个点选需要增加公差的尺寸实体,按规定给其增加公差,也可以对标有公差的尺寸的公差值和公差显示方式进行修改。     

基于SolidWorks的尺寸公差标注系统设计

利用数据库技术开发了尺寸公差动态查询模块。通过二次开发,将查询模块作为插件集成在SolidWorks环境下,实现了SolidWorks中动态查询尺寸公差和标注。     

新一代GPS的线性尺寸查询及标注系统设计

为解决线性尺寸标注不符合新一代产品几何技术规范(GPS)标准的问题,加快新一代产品几何技术规范标准体系的推广使用,基于WinCE的嵌入式技术开发了新一代GPS的线性尺寸查询及标注系统。系统中的公差原则及要求的设计,能够实现零件尺寸公差的自动化设计和查询,实现了线性尺寸设计的规范化和数字化。     

基于特征的装配尺寸链自动生成及分析的研究

讨论了尺寸和公差的工程语义的表达，提出零件邻接表和尺寸邻接表的装置体分级建模方式，并由封闭环信息优化调整装置体零件邻接表，在此基础上提出了根据产品的装配特征，形状特征，精度特征和指定的封闭环信息自动生成装置尺寸／公差链的算法。     

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）。     

基于仿真网格的引信虚拟试验研究

利用蒙特卡洛模拟实现对引信解除保险时间的计算机虚拟试验,以减少或部分替代高价值弹药的靶场射击试验.依据机械设计软件进行三维模型随机尺寸偏差的生成研究,建立了能生成具有一定概率分布特性的尺寸公差的系统;利用仿真网格技术构建了引信虚拟试验系统,并对某引信进行了多组尺寸偏差变化下的虚拟试验,验证了公差对引信解除保险时间的影响.     

尺寸公差的查询和自动标注

本文介绍了在AutoCAD2000中用VBA的数据库方法实现尺寸公差的实时查询,用ActiveX方法实现尺寸公差的自动标注,并将新增命令组成下拉菜单。     

Dimension and tolerance modeling and transformations in feature based design and manufacturing

This paper describes the development and application of a geometric dimension and tolerance (GD&T) model for use in both design and process planning. The model meets criteria for computability and compatibility with the Y14.5M standard. The model is first used to capture the designers GD&T scheme on a feature based design model, validate its completeness, and then transfer the GD&T to machining features extracted automatically by feature recognition. The model is based on relative degrees of freedom of geometric entities: feature axes, edges, faces and features-of-size. Dimension graphs are created based on the degrees of freedom for each control direction. Datum reference frames and standard tolerance classes are incorporated into the graph. The model allows dimension specification, dimension scheme modification, and dimension scheme validation. A methodology to automatically determine the GD&T of machining volumes obtained by feature recognition is also described.     

路径-维度GraphOLAP大规模多维网络并行分析框架

现实生活中大量数据都可以使用多维网络进行建模,如何更好地对多维网络进行分析至今仍是研究人员关注的重点.OLAP（联机分析处理）技术已被证实是对多维关系数据进行分析的有效工具,但应用OLAP技术管理和分析多维网络数据以支持有效决策仍旧是一项巨大的挑战.本文设计并提出了一种新的图立方体模型：路径-维度立方体,并针对提出的立方体模型将物化过程划分为关系路径物化与关联维度物化两部分,分别提出了物化策略并基于Spark框架设计了相关算法;在此基础上,我们针对网络数据设计并细化了相关的GraphOLAP（图联机分析处理）操作,丰富了框架的分析角度,提高了对多维网络的分析能力;最后,在Spark上实现了相关算法,通过对多个真实应用场景中的数据构建多维网络,在分析框架上进行了分析,实验表明我们提出的图立方体模型和物化算法具有一定有效性和可扩展性.     

Feature based 3D garment design through 2D sketches

This paper presents a new approach for intuitively modeling a three-dimensional (3D) garment around a 3D human model by two-dimensional (2D) sketches input. Our approach is feature based—every human model has pre-defined features, and the constructed garments are related to the features on human models. Firstly, a feature template for creating a customized 3D garment is defined according to the features on a human model; secondly, the profiles of the 3D garment are specified through 2D sketches; finally, a smooth mesh surface interpolating the specified profiles is constructed by a modified variational subdivision scheme. The resulting mesh surface can be cut and flattened into 2D patterns to be manufactured. Our approach provides a 3D design tool to create garment patterns directly in the 3D space through 2D strokes, which is a characteristic not available in other computer aided garment design systems. The constructed garment patterns are related to the features on a human model, so the patterns can be regenerated automatically when creating the same style of garment for other human models. Our technique can greatly improve the efficiency and the quality of pattern making in the garment industry.     

三维多元地学数据一体化显示框架设计

随着三维地质信息系统发展与应用的深入,对地学数据的可视化需求更加迫切。采用面向对象的思想设计并实现了一个可扩展的多元地学数据一体化显示框架。该框架主要划分为模型层、场景层和渲染层,使得数据与绘制流程分离。围绕此框架详细阐述了绘制管线、绘制过程的设计和多层次地学场景组织,满足地质多领域、多专题数据的统一显示与分析需要。基于此框架在OpenGL环境下开发了北京市三维城市地质信息管理与服务系统。     

3D-feature-based structure design for silicon fabrication of micro devices

To make MEMS structure design in a more intuitive way, and to support the “function to 3D shape to mask” design flow, a 3D feature based structure design framework and its corresponding key enabling techniques are presented on the basis of inverse design processes and top-down design methodologies. Driven by space mapping among function and structure, the feature model and its parameters are restricted with the bond graph represented simulation model, which is constructed with functional components in simulation library at the system-level. Conforming design rules, the hierarchic feature information model is established and finally can be cascaded down to a group of 3D feature nodes, which are all silicon fabrication oriented and defined on the top of CSG/B-rep 3D solid models. Surrounding this feature information model, the 2D mask deducing and fabrication parameters extraction at the fabrication-level can be performed for manufacturability checking, design/fabrication conflict feedback and fabrication process sequence generation. Taking a micro gap-closing actuator as an example, the structure design process is demonstrated in terms of this 3D feature modeling methodology.     

XSLT‐based evolutions and analyses of design patterns

Design patterns document flexible designs that may evolve over time. Design pattern evolution typically involves the addition or removal of a group of modeling elements, such as classes, attributes, operations, and relationships. However, the possible evolutions of each design pattern are often not explicitly documented. Missing part of the evolution process may result in inconsistent evolution. Pattern instances may interact with each other making the evolution of design patterns more error‐prone. Undetected design errors and inconsistencies may cause failures of systems. In this paper, we propose a service‐oriented architecture for design pattern evolution and analysis based on two‐level transformations, thus making the possible evolutions of each design pattern explicit. In addition, we automate the evolution processes as XSLT transformations that can transform the unified modeling language (UML) model of a design pattern application into the evolved UML model of the pattern. Both the original and evolved UML models are represented in the XML Metadata Interchange format to facilitate the transformations. Furthermore, we check the consistency of the evolution results using the semantic web checker based on the Java Theorem Prover. A case study on a large real‐world system is presented to illustrate and evaluate our approach. Copyright © 2009 John Wiley & Sons, Ltd.     

Pattern recognition with cerebellar model articulation controller and fractal features on partial discharges

This paper presents a new partial discharge (PD) pattern recognition method based on the cerebellar model articulation controller (CMAC). CMAC is an adaptive system by which defect types for partial discharge can be identified by referring to a table rather than by mathematical solution of simultaneous equations. CMAC maps input features of partial discharge into an input vector which is used to address a memory where the appropriate defect types are stored. Five types of defect models are well-designed on the base of investigation of many power apparatus failures. A PD detector is used to measure the raw three-dimension (3D) PD patterns, from which the fractal dimension, the lacunarity, and the mean discharges of phase windows are extracted as PD features. These critical features form the cluster domains of defect types. Using the characteristics of self-learning, association, and generalization, like the cerebellum of human being, the proposed CMAC-based pattern recognition scheme enables a powerful, straightforward, and efficient pattern recognition method. Moreover, the CMAC has the advantages of higher accuracy, shorter learning times, and noise tolerance, which are useful in recognizing the PD patterns of electrical apparatus. To demonstrate the effectiveness of the proposed method, comparative studies using a multilayer neural network (MNN) and K-means method are conducted on 200 sets of field-test PD patterns with high accuracy and high tolerance in noise interference.     

基于分形维数的属性约简

关于属性约简的算法已经提出了许多，基于粗糙集的属性约简算法就是其中的一类。但该类算法执行效率低且不一定得到最小约简。本文讨论了基于可辨识矩阵的属性频度算法（BDMF）并提出了基于分形维数的向后剔除属性约简算法（FDR）。仿真实验表明FDR比BDMF的运行效率高，且约简的效果更好。     

Optimal design of a high-speed slotless permanent magnet synchronous generator with soft magnetic composite stator yoke and rectifier load

This paper presents a specific design methodology of a DC generation system using a high-speed slotless generator with surface-mounted magnets and soft magnetic composite (SMC) stator yoke connected to a rectifier. The method is based on an analytical design model of the machine, an electrical model of the machine-rectifier system and a non-linear optimization procedure. The coupling between both models is achieved by a specific correction mechanism during the iterative process that performs an efficient convergence of the optimization procedure. The machine design model is derived from an analytical computation of the two-dimensional magnetic field distribution created by the magnets, the armature currents and the stator eddy currents that circulate in the SMC material. It has been cross-validated by 2D finite element analysis. The design approach is applied to the specifications of a 1.5 MW, 18,000 rpm slotless permanent magnet generator with a rated DC output voltage of 1500 V.