面向对弯曲件工艺交互设计的几何模型

计算机辅助工艺设计的主要任务是对被加工零件选择合理的加工方法和加工顺序。本文提出一种个用于变曲工步设计的几何模型，此模型已成功地用于汽车冲压件工艺卡创成系统中，解决了弯曲展开、弯曲工序设计，产品几何建模等关键技术。     

模具CAD／CAM系统中弯曲零件的几何描述和数据结构

在模兵CAD/CAM系统中,描述被加工零件的几何特征是最重要的方面之一,它是后续毛坯展开、工艺方案设计、模具参数计算、模具结构设计和模具图绘制的基础。本文重点讨论了典型弯曲件的几何特征,采用“弯曲树”的方法表示弯曲件的基本结构,并用表面模型描述了弯曲件的几何信息和拓扑信息。     

用于柔性生产线方案设计的分层工艺规划方法

在建立面向对象工艺模型的基础上，提出用于柔性生产线方案设计的分层工艺规划方法，即特征工艺设计、零件装夹定位规划、特征排序规划、工步排序规划、工序聚合规划等5个层次．采用基于黑板的递阶式层次推理结构，实现了综合排序策略，完成了用于柔性生产线方案设计的CAPP系统开发。     

一种模块化加工的CAPP系统方案策划和效果评估

一、引言 在摩托车发动机零件中,曲轴箱体和气缸头(图1和图2所示)是加工工艺比较复杂的两个零件,加工部位都在35个以上,涉及70多个加工工步的工艺卡片和加工程序设计,100多种刀具、量具的基本参数选型设计.     

面向STEP-NC的数据处理与仿真平台研发

介绍了STEP-NC数据模型的基本特点，分析了数控程序中的信息类型，研究了从STEP-NC文件中直接提取制造信息的基本方法，建立了基于特征的数控加工几何仿真模型，并讨论了相应的实现方法和技术。最后在ST-Developer环境下开发了一个基本的STEP-NC支持平台，其基本功能包括STEP-NC文件的翻译、制造信息的提取、组织和图形化显示等，并能以工步为单位进行仿真。     

铝合金整体壁板填料滚弯成型有限元仿真

提出整体壁板填料滚弯成型工艺,建立填料滚弯成型过程的有限元模型.仿真分析填料和工艺参数对滚弯成型壁板的等效应力、剪切应力、等效应变和回弹等的影响规律.结果表明：壁板滚弯成型时纵向筋条的等效应力和应变最大,填料填充滚弯提高壁板等效应力和塑性应变的均匀性,改善壁板弯曲半径的均匀性,提高弯曲件的几何精度;随着压下量的增大,壁板回弹率减小.     

基于MicroStation的自动编程系统中工步交叉的处理

一、引言 工步是加工表面不变、加工工具不变、切削用量不变的条件下所完成的那一部分工序.在数控车削加工过程中,由于受到工艺因素的影响,往往存在着工步交叉问题,即在两个或多个工步之间交替切削加工,这给自动编程系统带来了困难.因为自动编程系统编制出的程序是以工步作为基本单元,每个工步所对应的程序段又包括程序头、加工过程和程序尾三部分,各个工步之间一般采用单向链表结构顺序加工的形式.要实现各个工步之间的交叉加工对数控车自动编程系统提出了更高的要求.针对这一问题,作者采用双向链表结构,给出了数控车自动编程系统中工步交叉的算法,实现了自动编程中的工步交叉.     

国外基于特征设计的研究现状与展望

一、前言基于特征设计，简称特征设计。特征的概念是从工艺引出的，工艺规程是从毛坯到给定零件的转换过程，具体包括产品建模、选择机床、选择刀具组、选择加工时的装卡方案、确定切削序列和切削用量、设计夹具、确定刀具路径、编制数控机床加工程序等。为实现工艺规程的自动化，需要各种各样的信息，这些信息在设计好的零件三视图中已经存在，但可惜的是，当设计人员用几何实体造型方法在计算机上建立零件模型时，只保留了几何信息，而其他大量信息全丢失了！本文要讨论的特征设计恰恰能帮助我们克服这个问题。特征可以携带大量的工程信息…     

基于遗传算法的双目标作业调度优化

提出了一种双向调度遗传算法，用于解决多工艺路线的以缩小生产周期和工件准时交货为目标的作业调度问题．双向调度就是采用倒排法调度关键工件，使其准时交货；采用顺排法调度其余工件，利用剩余加工资源，使其尽旱完工．双向调度遗传算法就是用遗传算法搜索双向调度的最优解．设计了一种新的染色体编码方法，该方法直接把工艺路线和工序映射成字符串．并对该编码的交叉算子和变异算子进行了研究．仿真结果表明，该算法是可行的，在生产中有一定的优越性。     

基于Pro/ENGINEER的弯曲件展开长度计算

一、引言弯曲件的展开长度计算,是设计弯曲件冲压模具的一项重要内容。在利用Pro/ENGINEER的钣金功能进行钣金设计时,Pro/ENGINEER可以自动计算展开长度,但其计算方式比较单一,不能适应普遍的情况。本文探讨利用Pro/ENGINEER的钣金功能,通过设置自定义折弯表的方式,进行弯曲件展开长度计算的通用方法。     

Process planning and machining sequence

Most Computer Assisted Process Planning [CAPP] is of either the variant or generative type. The variant type makes use of the existing process plans in developing process plans for new parts based on the geometric similarities. The generative type process planning develops process plans from scratch based on geometric features to be generated in machining. Several software packages are available for developing process plans for cylindrical parts and prismatic parts. Studies on the application of Artificial Intelligence [AI] techniques in developing Expert Systems to prepare process plans are emerging. It is important to have a basis for determining the machining operation sequence in process planning. This paper outlines a method of determining the machining operation sequence in process planning using the principles of graph theory considering factors such as dimensional and geometrical tolerances, surface finish, accuracy and cost.     

Manufacturing preparation by use of product model in computer

This paper describes the general concept and the framework of a product model for design and manufacturing preparation. Machining preparation, such as process and operation planning, generation of NC cutter path, and geometrical and physical simulation of the machining operation, made by utilizing information stored in the preceding stages, are implemented at each stage. Finally the use of information is shown in a product model for off-line programming of robots and for geometric and physical simulation of robot operation.     

Delaunay三角网支持下的多边形化简与合并

多边形的化简与合并运算是自动化制图综合中的重要算子,这类算子的设计要基于多边形几何特征,拓扑特征的分析,还需要一种有力的空间数据模型用于支持多边形各弯曲特征部位之间,多边形与多边形之间,多边形的各岛屿之间邻近关系探测,鉴于Delaunay三角网的“最大最小角规则”和“外接圆规则”,使得其成为空产邻近分析的一种强有力工具,因此在二维空间建立约束Delaunay三角网模型和形式检索机制的基础上,系统地讨论了多边形弯曲特征的化简,夸大,以及邻近多边形合并的方法,并将多边形化简分解为“岛屿”选取,凹部填充,狭长区域中轴化,保留凹部的夸大,以及凸部的弃除等几个步骤完成,又将多边形合并区分为吸刷式,包络式,分解式等3种情形,同时给出了这些算法的实验结果。     

自动折弯生产线中逆跟随折弯回正运动模型研究

在简要介绍自动折弯生产线的布局的基础上,分析了自动折弯生产线的工作过程,根据前道折弯的折弯深度和折弯速度,建立折弯辅助机器人的逆跟随折弯回正运动模型,并基于该模型提出了折弯辅助机器人逆跟随折弯回正运动轨迹规划的方法,在折弯辅助机器人跟随折弯完成后,机器人Y、Z、A轴沿着前道折弯跟随的轨迹同时做逆跟随运动,将工件回正到前道折弯时的位置,微调后进行下一道折弯工序,节省了每道工序的加工时间。最后通过实际折弯加工的测试分析,验证了该运动模型的可行性,在保证折弯精度的同时提高了自动折弯生产线的工作效率。     

Construction-specific spatial information reasoning in Building Information Models

In recent years, there have been significant advances in modeling technology for object-oriented building products. However, the building models are still lacking of providing construction-specific spatial information required for construction planning. Consequently, construction planners visually analyze building product models and derive geometric characteristics such as bounded spaces and exterior perimeter to develop detailed construction plans. Such a process presents fragmented information flows, from building product information to construction planning, that rely on subjective decisions of construction planners. In order to overcome these drawbacks, this research proposes a geometric reasoning system that analyzes geometric information in building designs, derives the construction-specific spatial information, and uses the information to assist in construction planning. The scope of presented work includes detecting work packages formed by faces during construction, such as large work faces and bounded spaces, and using information in the work packages directly to support planning of selected indoor construction activities. The main features of the proposed system named Construction Spatial Information Reasoner (CSIR) include a set of relationship acquisition algorithms, building component relationship data structure, and interpretation of the relationship to support detailed construction activity planning. The relationship acquisition algorithms identify adjacency between building components that is stored in the relational data structure. Then, acquired adjacency relationships are transformed into a set of graphs that represent work packages. To implement the proposed approach, CSIR utilized a commercially-available Building Information Modeling (BIM) platform and the algorithms were imbedded to the BIM platform. For validation, CSIR was tested on a real commercial building. For interior ceiling grid installation activities, CSIR successfully detected existing work packages and analyzed the spatial characteristics impacting construction productivity. The major contribution of the presented research would be to enable a realistic analysis of building geometric condition that is not possible in current BIM and a seamless information flow from building product information to construction process plans. These can potentially reduce current manual and error-prone construction planning processes. Limitations and future research suggestions are also presented.     

Numerical and experimental study of the virtual quadrupedal walking robot-semiquad

SemiQuad is a prototyped walking robot with a platform and two double-link legs. Thus, it is a five-link mechanism. The front leg models identical motions of two quadruped's front legs, the back leg models identical motions of two quadruped's back legs. The legs have passive (uncontrolled) feet that extend in the frontal plane. Due to this the robot is stable in the frontal plane. This robot can be viewed as a "virtual" quadruped. Four DC motors drive the mechanism. Its control system comprises a computer, hardware servo-systems and power amplifiers. The locomotion of the prototype is planar curvet gait. In the double support our prototype is statically stable and over actuated. In the single support it is unstable and under actuated system. There is no flight phase. We describe here the scheme of the mechanism, the characteristics of the drives and the control strategy. The dynamic model of the planar walking is recalled for the double, single support phases and for the impact instant. An intuitive control strategy is detailed. The designed control strategy overcomes the difficulties appeared due to unstable and under actuated motion in the single support.Due to the control algorithm the walking regime consists of the alternating different phases. The sequence of these phases is the following. A double support phase begins. A fast bend and unbend of the front leg allows a lift-off of the front leg. During the single support on the back leg the distance between the two leg tips increases. Then an impact occurs and a new double support phase begins. A fast bend and unbend of the back leg allows the lift-off of the back leg. During the single support on the front leg the distance between the two leg tips decreases to form a cyclic walking gait.The experiments give results that are close to those of the simulation.Funding for SemiQuad was primarily provided by the CNRS and the region Pays de La Loire.     

A layered architecture for manufacturing operation planning

Machining operation planning involves the selection and sequencing of machining operations for fabricating a workpiece. It is the first step in the process of generating a detailed process plan for a workpiece. In the past five years, several knowledge-based systems have been developed. Two knowledge representation schemes are employed: production rules and frames. Each of these exhibits some general properties of human information processing but neglects the other. None of the existing systems is able to solve real-world problems. The main focus of this paper is on a layered architecture for manufacturing knowledge representation and automated reasoning for operation planning. This can be addressed through a discussion of both the knowledge representation structure and the inference mechanism. The proposed layered architecture has been implemented on a microcomputer using PROLOG. The results are satisfactory.     

The IFC-based path planning for 3D indoor spaces

Path planning is a fundamental problem, especially for various AEC applications, such as architectural design, indoor and outdoor navigation, and emergency evacuation. However, the conventional approaches mainly operate path planning on 2D drawings or building layouts by simply considering geometric information, while losing abundant semantic information of building components. To address this issue, this paper introduces a new method to cope with path planning for 3D indoor space through an IFC (Industry Foundation Classes) file as input. As a major data exchange standard for Building Information Modeling (BIM), the IFC standard is capable of restoring both geometric information and rich semantic information of building components to support lifecycle data sharing. The method consists of three main steps: (1) extracting both geometric and semantic information of building components defined within the IFC file, (2) discretizing and mapping the extracted information into a planar grid, (3) and finally finding the shortest path based on the mapping for path planning using Fast Marching Method. The paper aims to process different kinds of building components and their corresponding properties to obtain rich semantic information that can enhance applications of path planning. In addition, the IFC-based distributed data sharing and management is implemented for path planning. The paper also presents some experiments to demonstrate the accuracy, efficiency and adaptability of the method. Video demonstration is available from http://cgcad.thss.tsinghua.edu.cn/liuyushen/ifcpath/.     

Assembly operation process planning by mapping a virtual assembly simulation to real operation

Virtual assembly has been widely used in product development. However, virtual operation and actual operation are different in time and space, the simulation of interactive virtual assembly cannot support the assembly operation's process planning directly. In this paper, the solution for assembly operation's process planning is developed based on interactive virtual assembly. According to the solution, interactive assembly operation is used to obtain the actions of operation sequence. The actions are mapped into the data of a real operation action to obtain real operation actions. Then assembly operation cards can be obtained. To support the assembly operation actions obtained through virtual assembly simulation, a product assembly model is proposed. An operation semantic model is used to replace the geometric constraint model of assembly, which contains several ordered geometric constraints and some engineering restriction conditions. To test the solution and the models, one process planning example of an automobile engine is introduced. The results verified the feasibility and the effectiveness of the methods.     

Extraction of manufacturing details from geometric models

The potentials of geometric models as source representations for the generation of manufacturing details in discrete production processes have not been fully exploited. The objective of this paper is to utilize the geometric data base in the CAD system in production and manufacturing applications such as group technology, process planning, etc. The workpiece is represented as a syntactic pattern made up of geometric primitives. The applications presented in this paper are: (1) shape classification for group technology and process selection and (2) procedure for representation and machining of excess material. The procedures described offer a direct link between geometric models and computer-aided manufacturing.