虚拟环境中的产品装配技术

 利用虚拟环境作为人机界面来协助用户完成产品的装配活动是一个新的研究方向。本文主要介绍了在虚拟环境中进行产品装配所采用的一些技术,并着重讨论了虚拟装配的关键内容－虚拟装配规划系统的结构、功能、优点和存在问题。最后还了一个典型系统＝虚拟装配设计环境ＶＡＤＥ的体系结构和主要特点。     

基于产品配合图的装配顺序自动规划

装配顺序规划( ASP) 是基于装配建模的装配工艺顺序的自动规划生成, 是DFA( 面向装配的设计) 的关键技术之一。本文采用配合条件法进行装配顺序求解, 装配体采用其部件与部件间的配合关系来描述, 从部件间的配合关系可得到其装配体配合图。本文还在原算法的基础上添加了一些约束来降低算法的计算量, 使得算法更为简洁。该法在AutoCAD®设计平台上实现, 并采用装配体实例加以检验。     

Assembly modeling as an extension of feature-based design

The advantages and limitations of procedural and declarative approaches for product modeling are discussed. Concepts are developed for modeling all levels of product relations with a uniform set of structures and relationships. It is shown that five basic structures,Part-of, Structuring relation, Degrees of freedom, Motion limits, andFit can be used to define relationships between assemblies, parts, features, feature volume primitives, and evaluated boundaries. Generic relations which facilitate constraint specification between target and reference entities are also presented. Methods for the derivation of the location of an assembly unit from high level constraint specifications, such as mating conditions, and techniques for determining the degrees of freedom, motion limits, and assemblability are required. This can be done by uni-directional parameter derivation in the procedural approach, or by symbolic geometric reasoning or numerical equation solution in the declarative approach. The former is less expensive, easy to implement, avoids conflicts, but leads to combinatorial explosion. The latter is general, flexible, decouples constraint specification from validation, but is expensive, and may require conflict resolution.     

支持操作的装配仿真技术研究

 装配仿真作为一种可视化工具 ,能适时检测和改进产品可装配性 ,是DFA研究的基础关键技术。通过建立装配操作模型 ,实现对装配操作、装配工具、装配夹具等信息的集成 ,并将产品装配环境和装配过程有机地结合在一起 ,实现高层次装配仿真。所提出的算法均已应有于DMAS系统中 ,取得了良好的实际效果。     

Stochastic assembly line balancing using beam search

This paper presents a beam search-based method for the stochastic assembly line balancing problem in U-lines. The proposed method minimizes total expected cost comprised of total labour cost and total expected incompletion cost. A beam search is an approximate branch and bound method that operates on a search tree. Even though beam search has been used in various problem domains, this is the first application to the assembly line balancing problem. The performance of the proposed method is measured on various test problems. The results of the computational experiments indicate that the average performance of the proposed method is better than the best-known heuristic in the literature for the traditional straight-line problem. Since the proposed method is the first heuristic for the stochastic U-type problem with the total expected cost criterion, we only report its results on the benchmark problems. Future research directions and the related bibliography are also provided in the paper.     

机械产品虚拟装配智能导航技术的研究

通过对机械产品虚拟装配过程中装配关系的分析,在理解与识别设计者的装配操作和意图基础上,对共线约束和共面约束的智能导航进行了深入研究,实现了机械产品虚拟装配的智能导航.该方法有助于在虚拟装配环境下快速准确地进行零部件虚拟装配,提高产品设计效率.     

Non-conforming mesh gluing in the finite elements method

A methodology to connect two or more non-conforming meshes generated from a geometric model is presented. The problem leads to a variational problem subject to constraints. The emphasis of the work is on constraints construction. Two methods, namely, discrete connection and continuous connection, are developed. The relation with hybrid formulations is considered and two application examples are presented.     

一种新的几何约束系统参数取值范围的计算方法

在利用参数化CAD系统进行图形设计的过程中,通过修改图形对象的可变参数重新生成图形是最常见的一种操作。但用户在改变参数的过程中,由于事先并不知道有效的参数值,也没有任何引导信息,导致了用户只能盲目地不断输入参数值,通过反复输入参数值来满足约束关系的需要。该文将结构约束引入参数有效取值范围求解的范畴,并提出了确定一类常用的二维参数化CAD模型中参数的有效范围的计算方法和算法。算法复杂度为O（n2）。     

先进制造：将虚拟现实技术与快速原形技术应用于微电子机构系统设计

提出了用虚拟现实技术实现ＭＥＭＳ的快速原形设计的思想,并具体给出了虚拟环境中的实现步骤。核心是在虚拟环境中实现ＭＥＭＳ器件的部件设计,拟实组装,拟实运行。进一步,构建了虚拟现实实验平台;并在此平台上实现了微马达和微泵的心实运行及一个拟产组装的例子,从而验证了上述用虚拟现实技术实现ＭＥＭＳ的快速原形设计的可行性及相应实现步骤的正确性。     

面向功能的三维装配公差链的自动生成

 基于TTRS理论,提出了3类变动几何约束.由CAD中的装配信息可唯一确定配合树(MT),分析了配合树的性质,配合树之间通过互参考变动几何约束彼此连接构成回路.基于配合树,给出了的回路和三维装配公差链的生成方法.实例分析验证了此方法的有效性.     

一种新型纹织CAD/CAM电脑意匠系统

介绍了一种新的电脑意匠系统 .论述了目前先进的图像处理技术如边缘检测、灰度自动分级和伪彩色处理在纹织CAD/CAM电脑意匠系统中的应用及其对系统改造和功能完善的实施方法 .通过高斯拉普拉斯组合算子的去噪处理 ,使原来的人工修图可以由计算机自动完成 .灰度自动分级使计算机可以预览产品的最后效果 .伪彩色处理可以获得良好的人机界面 .