The auto-generation of analysis models from product definition data

This paper describes a feature-based methodology for generating computer models for analysis from product definition data. Given the product definition data, the development of analysis models of the product suitable for performance analysis is a time-consuming task that requires a considerable level of expertise and tedious feature modifications. A feature-based geometric reasoning technique is developed that can be used to reduce the lead time of analysis of models generated from product definition data and subsequently to shorten the process time of CAE (computer aided engineering) analysis.     

计算机辅助辊锻模具设计通用系统的研究

本文研究了制坯辊锻模具的计算机辅助设计通用软件系统,实现了辊锻过程的全部设计计算与绘制图纸的自动化。对于欲用辊锻工艺制坯的任意形状与尺寸的模锻件,只要输入相应的描述锻件几何形状用原始数据及某些必要的参数,电子计算机就可以快速、精确地完成从工步方案选择到模具尺寸计算的全部设计任务,并自动绘制出可供生产用的辊锻工步图与模具图。本文在描述锻件几何状形时采用了等截面体、变截面体、旋转体等三种形状体的组合法,使得能够用较少的原始数据描述各种不同形状的锻件。在简化锻件截面图时,本文提出了自动简化数学模型,明显地提高了设计效率。     

基于计算几何的曲面造型方法研究

以Pro/Engineer和UGNX为代表的计算机辅助设计和辅助制造软件,在制造行业已经成为产品设计和产品制造工程师的重要工具。这些CAD/CAM软件都必须能够胜任曲面造型的功能,它是产品三维设计的必然前提,因此曲面造型成为计算机辅助几何设计和计算机图形学的一项研究重要内容,而计算几何正是对曲面造型进行研究的数学方法。通过对曲面造型和计算几何的相关概念的介绍,详细阐述了基于计算几何方法建立曲面参数曲线的各种数学建模过程。这些数学建模方法能为各种CAD/CAM系统实现曲面功能提供理论指导。     

A study of workspace and singularity characteristics for design of 3-DOF planar parallel robots

A study of workspace and singularity characteristics is presented for two common types of 3-DOF planar parallel robot manipulators. The robots considered feature a kinematic structure with three in-parallel actuated, R-R-R, and R-P-R serial chain geometries. In this study, computer simulations aided with graphic visualization were used to characterize the complete pose workspace (for ranges of both position and orientation) and the singularity inherent to the systems. Parametric studies have also been performed to ascertain the way in which both characteristics vary with respect to various geometric parameters such as pivot locations, link lengths, and size of end-effector. Results are shown by way of a unique composite ratio of the available workspace to the density of singularity within that workspace, which can be used to optimize the geometry of the robots in design.     

计算几何在测试计量技术中的应用--求解最大内接圆

本文介绍了采用计算几何知识求解最大内接圆的新方法,该方法摆脱了传统的用坐标及函数处理几何问题的常规,从图形的崭新思路分析了最大内接圆的准确中心,并且提出了一种删除无关数据点的原则、可将采样点数减至十分之一以下。相应算法的运算时间比以往的算法快１５倍以上。     

基于UML的计算机辅助选择装配系统分析与建模

为了解决制约计算机辅助选择装配技术发展的建模问题,提出了一种基于统一建模语言(UML)的计算机辅助选择装配系统的分析与建模方法.通过使用UML完成计算机辅助选择装配系统的用例建模、静态建模和动态建模,使系统分析与设计更加文档化、可视化和标准化,为软件开发奠定了良好的基础.     

Automatic simplification of solid models for engineering analysis independent of modeling sequences

Although solid models can represent complex and detailed geometry of parts, it is often necessary to simplify solid models by removing the detailed geometry in some applications such as finite element analysis and similarity assessment of CAD models. There are no standards for judging the goodness of a simplification method, but one essential criterion would be that it should generate a consistent and acceptable simplification for the same solid model, regardless of how the solid model has been created. Since a design-feature-based approach is tightly dependent on modeling sequences and designer’s modeling preferences, it sometimes produces inconsistent and unacceptable simplifications. In this paper, a new method is proposed to simplify solid models of machined parts. Independently of user-specified design features, this method directly recognizes and generates subtractive features from the final model of the part, and then simplifies the solid model by removing the detailed geometry by using these subtractive features. This paper was recommended for publication in revised form by Associate Editor Jeong-Sam Han Yoonhwan Woo is an assistant professor of Mechanical Systems Engineering at Hansung University in Korea. He received his Ph.D. in Mechanical Engineering from Colorado State University in 1999, the M.S. in Mechanical and Aerospace engineering from Illinois Institute of Technology in 1995, and the B.S. in Precision Mechanical Engineering from Hanyang University, Korea, in 1993. He also has been a software engineer of ACIS development team in Spatial Corporation, USA. His research interests include geometric and solid modeling and computer aided process planning.     

微机在压力容器应力测试中的应用

针对压力容器传统应力测试方法所存在的弊端，采用软硬件相结合的滤波方法，开发了以计算机为核心的应力自动测试系统，该系统可有效地消除系统噪声等污染源的影响，成功实现了对微弱信号的自动采集、处理和输出。     

计算机技术用于压力容器应力测试

针对压力容器传统应力测试方法所存在的弊端，采用软硬件相结合的滤波方法，开发以计算机为核心的应力自动测试系统。该系统可有效地消除系统噪声等污染源的影响，成功实现对微弱信号的自动采集、处理和输出。     

计算机辅助装配顺序规划研究综述

装配过程的计算机辅助设计一直是计算机辅助工程的一个薄弱环节,本文重点针对计算机辅助装配顺序规划的研究,按照时间顺序和方法特点对各种有代表性的研究方法进行了分类介绍和剖析,最后总结出计算机辅助装配顺序规划研究中存在的不足。     

Generation of an STL File from 3D Measurement Data with User-Controlled Data Reduction

Reverse engineering is a methodology for constructing com-puter- aided design (CAD) models of physical parts by digitising an existing part, creating a computer model and then using it to manufacture the component. When a digitised part is to be manufactured by means of rapid prototyping machines such as stereolithography apparatus (SLA) and selective laser sintering equipment (SLS), etc., it is not necessary to construct the CAD model of a digitised part. This can be achieved by the proposed novel method which can construct an STL file (the de facto file format for rapid prototyping machines) directly from digitised part data. Furthermore, the STL file can be constructed with a significant data reduction at the users’ discretion.     

Automatic recognition of myeloma cells in microscopic images using bottleneck algorithm,modified watershed and SVM classifier

Plasma cells are developed from B lymphocytes, a type of white blood cells that is generated in the bone marrow. The plasma cells produce antibodies to fight with bacteria and viruses and stop infection and disease. Multiple myeloma is a cancer of plasma cells that collections of abnormal plasma cells (myeloma cells) accumulate in the bone marrow. The definitive diagnosis of multiple myeloma is done by searching for myeloma cells in the bone marrow slides through a microscope. Diagnosis of myeloma cells from bone marrow smears is a subjective and time‐consuming task for pathologists. Also, because of depending on final decision on human eye and opinion, error risk in decision may occur. Sometimes, existence of infection in body causes plasma cell's increment which could be diagnosed wrongly as multiple myeloma. The computer diagnostic process will reduce the diagnostic time and also can be worked as a second opinion for pathologists. This study presents a computer‐aided diagnostic method for myeloma cells diagnosis from bone marrow smears. At first, white blood cells consist of plasma cells and other marrow cells are separated from the red blood cells and background. Then, plasma cells are detected from other marrow cells by feature extraction and series of decision rules. Finally, normal plasma cells and myeloma cells could be classified easily by a classifier. This algorithm is applied on 50 digital images that are provided from bone marrow aspiration smears. These images contain 678 cells: 132 normal plasma cells, 256 myeloma cells and 290 other types of marrow cells. Applying the computer‐aided diagnostic method for identifying myeloma cells on provided database showed a sensitivity of 96.52%; specificity of 93.04% and precision of 95.28%.     

Rapid one-of-a-kind production

To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study, the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy, which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this paper. This system consists of a number of inter/intranet based computer models or subsystems for supporting rapid development of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental product development strategy” and an integrated product data structure called “product production structure”. Some industrial implementations of the proposed system, product development strategy and product data structure are also reported in the paper.     

绿色产品的计算机辅助设计研究

为了探讨将计算机辅助设计技术应用于绿色产品设计中,提出“绿色产品计算机辅助设计”的定义和方法。绿色产品的计算机辅助设计是利用计算机来协助设计人员进行产品设计,并以资源可持续利用和环境保护为目标的现代设计方法和技术。当产品的设计方案出现矛盾时,计算机系统能够对各项设计进行分析、评估和修改,最终实现以绿色为先导的产品优化设计。     

Rapid one-of-a-kind production

To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study, the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy, which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this paper. This system consists of a number of inter/intranet based computer models or sub-systems for supporting rapid development of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental product development strategy” and an integrated product data structure called “product production structure”. Some industrial implementations of the proposed system, product development strategy and product data structure are also reported in the paper.     

A CAD-CAM methodology to produce bone-remodelled composite femurs for preclinical investigations.

Femoral bone remodelling, following total hip arthroplasty, is a clinically observed phenomenon attributed to the changed stress environment of the postoperative implanted hip. While this process cannot be avoided, there is concern as to its consequences on the long-term survival of hip joint replacements. Previous methods of studying remodelling, such as clinical or animal-based studies, or finite element analyses, have their limitations. The aim of this study is to develop experimental specimens incorporating bone resorption features typical of clinically successful implants. This work describes the use of computer aided design/manufacturing methods (CAD-CAM) to produce these specimens, based on modifying commercially available composite femurs. The procedures are investigated and verified for two different designs of cemented prostheses (Lubinus SPII and Muller Curved). Quantitative clinical data is used to define the remodelled geometry of a CAD model of the femur for each stem design. Composite femur specimens are machined using a three-axis milling machine, where each specimen can be accurately positioned using a custom-designed jig and a digitizer system. The accuracy of the process is assessed by analysing the deviation of the digitized premachined and postmachined surfaces of each specimen in relation to the CAD model. The results demonstrate that the procedure can be used for developing in vitro specimens with bone resorption features. These specimens are proposed as a useful tool for performing preclinical trials, such as load transfer or longevity/stability testing, with the advantage of modelling a long-term clinical situation, rather than solely analysing implanted femurs in an immediate postoperative state.     

面向虚拟装配的装配序列规划技术研究

目前产品装配序列完全通过自动推理获得的方法工程实用性不高,据此,提出将计算机的辅助知识导航与人的决策相结合的方法,通过虚拟环境下的人机协同方式来解决装配序列规划问题。首先给出了装配序列知识导航的框架结构,提出了根据当前装配状态,将几何层和语义层知识规则交替运用、递进分层的装配序列动态导航算法;给出了几何层推理所运用的优先级判断准则和假设,并对语义层规则的4层框架描述方法进行了说明;最后通过实例进行了验证。     

计算机辅助几何法分析4-DOF并联机器人

提出运用计算机辅助几何法来研究新型四自由度并联机器人的型综合问题,利用在CAD软件草图环境下建立的并联机器人模拟机构,基于并联机器人的模拟机构,综合出多种新型四自由度机构,并用计算机模拟法,分析了动平台的运动特性。模拟结果表明,计算机辅助几何法的应用不但大大简化了并联机器人机构型综合的难度,而且快捷直观,值得推广。     

基于参数化的玻壳模具关键成型数据计算机辅助设计计算

结合彩色玻壳模具计算机辅助设计计算系统的开发,介绍产品或工程设计中以完成关键设计数据计算为主要目标的参数化设计.     

A comparison between automatically generated linear and parabolic tetrahedra when used to mesh a human femur

Finite element models of bone segments generated from computed tomography data using automatic mesh generation algorithms are becoming common not only in research but also in clinical applications such as computer aided orthopaedic surgery. Especially in the case of the latter application, the models cannot be verified against an experimental measurement, therefore their inherent accuracy should be well known before drawing conclusions based on the calculated results. This study was carried out to assess the performance of tetrahedral solid finite elements with linear and quadratic displacement functions when they are used to mesh the human femur in conjunction with automatic mesh generator methods. Ten-node quadratic tetrahedra (T10) having parabolic displacement functions were compared with four-node linear tetrahedron elements (T4) on the basis of accuracy and central processing unit (CPU) time. From the analyses of 11 finite element meshes, it was concluded that linear tetrahedral elements should be avoided and quadratic tetrahedral elements ought to be chosen for the purposes of finite element analysis of the human femur. When incremental loading and iterative solution is necessary, the coarsest possible T10 mesh compatible with accuracy is needed to minimize computer capacity and CPU time.