浅议CAD与机械制图

CAD是机械制图的重要工具,是体现机械制图的具体方式;而机械制图是CAD的功能体现,成果展示;二者有机结合,共同完成工程上的设计任务。     

火炮系统总体优化设计的形式方法探讨

提出了一个用于总体优化设计的形式方法──设计方案空间方法，形式地描述地面火炮系统设计过程，找出总体设计、评价、优化的关系，以形成集成ＣＡＤ系统，支持地面火炮系统总体优化设计。实验系统用ＦＯＲＴＲＡＮ和Ｃ语言编写，运行在ＳＧＩ工作站上。     

Mechanical design methodology: Implications on future developments of Computer-Aided Design and Knowledge-Based Systems

The Current Computer-Aided Design (CAD) and Knowledge-Based Systems (KBS, expert systems) tools are changing mechanical engineering design. Future development and integration of these technologies is dependent on an understanding of the methodology of the mechanical design process, an area of little study and one that is poorly understood. This paper reports on the progress of an effort to understand how practicing engineers perform design. The approach is to record engineers' verbalization of their solution of carefully constructed design problems. The recordings are reduced to determine the intellectual tasks and problem-solving methods used. The results will determine what needed capabilities future intelligent CAD systems will need to aid design engineers.     

Factors that affect planning in a knowledge-based system for mechanical engineering design optimization with application to the design of mechanical power transmissions

Intelligent computer-aided design (CAD) emulates the human activity of design so that production planning, decision making, and inventive design can be performed by computers.Based on the history of human experience in engineering design, a formalized and systematic approach to design should include procedures from (1) conceptual design, (2) layout design, and (3) numerical optimization. The highest level within such a system should be responsible for specifying and symbolically optimizing skeleton structures of generic (nonspecific) elements within the design process that are eventually to be specified uniquely (pinned down) and ultimately optimized numerically. Planning plays a key role in such a system.Planning has been utilized as a tool for process organization within the knowledge domains of chemical engineering, electrical engineering, manufacturing, as well as for general problem formulation and solution. State estimation, subtask scheduling, and constraint propagation have been found to be factors of prime importance in this type of problem.Problems associated with the implementation of a planning strategy within a knowledge-based system for mechanical engineering design optimization are discussed. A hypothesis for planning is put forth and examined within the context of a model of the mechanical design optimization process. An example that demonstrates the applicability of this approach to mechanical power transmission design is considered.     

虚拟原型多体动力学约束模型研究

并行工程角度出发的机械虚拟原型是集成了产品的设计、分析,不断迭代、优化的过程,模型的协调一致性是保证设计过程完整的关键,如产品模型在CAD模型与机械多体动力学模型中的一致性表达。在这种观点下,该文提出在建立基于组件的机械系统虚拟原型时,从CAD中抽取多体动力学模型构件的物理属性,研究了国产三维实体设计软件CAXA环境下,基于多刚体系统动力学笛卡尔方法,从CAD模型映射多刚体动力学分析模型语义的实现方案。分析了多刚体系统动力学模型语义下,多体动力学约束模型坐标基变换关系的抽取。实验结果表明,从CAD中抽取多体动力学模型的物理属性的方案是可行的。可以用于建立基于组件的多体系统虚拟原型的分析模型,实现自主开发设计、分析集成的机械虚拟原型。     

Collaborative design: Improving efficiency by concurrent execution of Boolean tasks

Computer-Aided Design (CAD) applications provide design and engineering professionals with various computer-based tools to perform design activities. As efficiency is one of the most important requirements in most design tasks, in this article, we contribute a novel collaborative design approach to improving efficiency, where a complex design task can be divided and executed concurrently by multiple collaborative designers. This approach is particularly effective for design tasks where Boolean operations – widely supported by most CAD applications – are heavily used in design activities, such as architecture design, mechanical design and digital media design. We have designed and implemented a prototype system CoAutoCAD to test the approach and to demonstrate a variety of collaborative design activities.     

用于变型设计的派生式CAD方法

本文将CAPP方法移植到CAD技术中，实现了用于变型设计方案的派生式CAD方法，讨论了派生式CAD在功能变型设计和结构变型设计的应用。文中详细比较了派生式CAPP与产品变型设计的工作过程，给出了基于相似性原理的产品分类编码方法，提供了一套相对独立的产品变型设计特性代码操作机制。     

Integrated CAD development for building services engineering

The potential benefits of CAD in building design are well established. In reality most production CAD systems are developed in response to the particular requirements of users who are architects or building engineers. These requirements are often fragmented. They relate to different aspects of the complete building engineering design cycle and are often specified by different users at different moments in time. The role of the CAD systems developer is to design a coherent software system and to establish a consistent set of user interface conventions with which an integrated solution of these different requirements can be provided. This paper describes how this methodology has been successfully applied to an important aspect of CAD relating to building services engineering.     

Knowledge engineering and CAD

The technology of Computer Aided Design (CAD) has rapidly been changing the processes of machine design, especially in detail and production design. Conventional CAD systems are necessary in production design where precise geometrical data are indispensable, but we can point out some problems of those systems from a point of view of the total machine design process. Though the main aim of introducing CAD systems is to increase designers' creativities, it is doubtful whether designers are really supported by such CAD systems. We think that knowledge engineering is useful to improve such situations. In this paper, we discuss these problems and we study the feasibilities of future CAD systems that can really help designers very intelligently and efficiently. We also show some results of our experimental systems applying knowledge engineering.     

Intelligent computer-aided-design systems: a synergical approach of artificial intelligénce and engineering

A synergism has begun to surface from the artificial intelligence (AI) and engineering communities: an effort to apply AI techniques to engineering problem-solving activities, and to study problems arisen from various engineering fields as a way to develop AI theories and methodologies. This paper first discusses the needs of such a synergical approach and identifies in a broad perspective some AI techniques currently being applied to engineering. It then describes a system, called KREATOR, which applies qualitative reasoning, a subfield of AI, to computer-aided design (CAD). The key observation is that an engineer designer's qualitative knowledge can offer a good basis for the reasoning of device behaviors. Such knowledge, however, is not captured by conventional CAD systems for lack of good representations. KREATOR is a knowledge capturing scheme that allows the designers to record their qualitative knowledge of how mechanical devices behave, KREATOR then automatically generates qualitative simulations.     

基于模板的港口码头三维结构CAD/CAE 集成技术

针对港口码头结构CAD 几何模型生成CAE 单元模型,工程荷载CAD 模 型创建CAE 荷载模型,和CAE 分析结果与CAD 模型的关联关系等问题,利用模板的模型 独立性、规则性和可执行性等特性,研究了基于模板的港口码头三维结构CAD/CAE 集成技 术,定义了截面草图、三维实体和构件等多种CAD 建模模板,定义了机械草图和荷载等多 种荷载建模模板,定义了CAE 分析规则,实现了CAD 几何模型自动生成CAE 单元模型的 功能,定义了荷载转换规则,实现了工程荷载CAD 模型自动创建CAE 荷载模型的功能, 定义了整体模型模板,建立CAE 分析结果与CAD 模型的多对一关系,以此实现了港口码 头三维结构CAD/CAE 集成系统,大大提高了港口码头的设计效率,降低了设计人员的设计 难度,减少了设计错误。     

基于哈希的二维工程 CAD 图纸检索技术

针对企业在设计创新过程中大量采用已有计算机辅助设计(CAD)图纸进行设计重 用的情况,提出了一种基于哈希的二维工程 CAD 图纸检索方法。首先基于环形分割算法提取 工程 CAD 图纸中每个组件对象几何特征;基于传统 LBP 算子提出了一种局部拓扑矢量量化模 式(T-LVQP),实现对各个组件拓扑特征的提取;然后基于协方差描述符融合几何特征和拓扑特 征,通过 LBG 算法将所有组件按照几何特征分组后得到工程 CAD 图纸的特征向量表达;最后 通过迭代量化哈希算法生成图纸的哈希序列。实验结果表明,该算法检索速度快、准确度高, 对于二维工程 CAD 图纸具有较好的检索效果。     

Engineering knowledge formalization and proposition for informatics development towards a CAD-integrated DfX system for product design

Target design methodologies (DfX) were developed to cope with specific engineering design issues such as cost-effectiveness, manufacturability, assemblability, maintainability, among others. However, DfX methodologies are undergoing the lack of real integration with 3D CAD systems. Their principles are currently applied downstream of the 3D modelling by following the well-known rules available from the literature and engineers’ know-how (tacit internal knowledge).This paper provides a method to formalize complex DfX engineering knowledge into explicit knowledge that can be reused for Advanced Engineering Informatics to aid designers and engineers in developing mechanical products. This research work wants to define a general method (ontology) able to couple DfX design guidelines (engineering knowledge) with geometrical product features of a product 3D model (engineering parametric data). A common layer for all DfX methods (horizontal) and dedicated layers for each DfX method (vertical) allow creating the suitable ontology for the systematic collection of the DfX rules considering each target. Moreover, the proposed framework is the first step for developing (future work) a software tool to assist engineers and designers during product development (3D CAD modelling).A design for assembly (DfA) case study shows how to collect assembly rules in the given framework. It demonstrates the applicability of the CAD-integrated DfX system in the mechanical design of a jig-crane. Several benefits are recognized: (i) systematic collection of DfA rules for informatics development, (ii) identification of assembly issues in the product development process, and (iii) reduction of effort and time during the design review.     

A Data Manager for Engineering Applications

Efficient data management is crucial to the success of a CAD/CAM system.Traditional databas systems,designed to deal with only regular and structural data,cannot efficiently manage design data.In this paper,we present a data manager called EDBMS/2,which has been developed by our laboratory for engineering support applications.EDBMS/2 has a data model that combines features of both relational and semantic ones and owns flexible abilities for modeling engineering data,such as variable-length data processing,integrated management of structuresd data and unstructured data,and composite object handling.Mechanisms based on DBV and DBV graph concepts,proposed in EDBMS/2 ,make EDBMS/2 own powerful abilities for version management and run efficiently.By now,EDBMS/2 has been used successfully in EDCADS(integrated Electronic Devices CAD environment)project and as a lower level support to develop and object-oriented DBMS for mechanical engineering.     

Comparing two types of engineering visualizations: task-related manipulations matter

This study focuses on the comparison of traditional engineering drawings with a CAD (computer aided design) visualization in terms of user performance and eye movements in an applied context. Twenty-five students of mechanical engineering completed search tasks for measures in two distinct depictions of a car engine component (engineering drawing vs. CAD model). Besides spatial dimensionality, the display types most notably differed in terms of information layout, access and interaction options. The CAD visualization yielded better performance, if users directly manipulated the object, but was inferior, if employed in a conventional static manner, i.e. inspecting only predefined views. An additional eye movement analysis revealed longer fixation durations and a stronger increase of task-relevant fixations over time when interacting with the CAD visualization. This suggests a more focused extraction and filtering of information. We conclude that the three-dimensional CAD visualization can be advantageous if its ability to manipulate is used.     

Design frameworks for concurrent engineering

As technological tasks in manufacturing environment have become progressively complicated, today's designers are confronted not only with increasing complexity of product designs but also with constantly increasing number and complexity of specialized design tools. The entire design process has consequently become very complicated. A large number of highly specialized design tools have to be developed to meet the technological needs of complex design tasks, and integrated into a computer-aided design (CAD) framework to provide better services to users. The concept of the framework may be of special interest to those who try to implement the philosophy of concurrent engineering, because a large number of design tools are required during the design phase to examine the entire aspects of a product's life-cycle in a coherent way. This paper identifies the needs and requirements of such CAD frameworks for concurrent engineering environment and discussed the object-oriented paradigm which has several salient features applicable to the development of control mechanisms for CAD tools within the framework.     

Design parameterization and tool integration for CAD-based mechanism optimization

This paper presents an open and integrated tool environment that enables engineers to effectively search, in a CAD solid model form, for a mechanism design with optimal kinematic and dynamic performance. In order to demonstrate the feasibility of such an environment, design parameterization that supports capturing design intents in product solid models must be available, and advanced modeling, simulation, and optimization technologies implemented in engineering software tools must be incorporated. In this paper, the design parameterization capabilities developed previously have been applied to support design optimization of engineering products, including a High Mobility Multi-purpose Wheeled Vehicle (HMMWV). In the proposed environment, Pro/ENGINEER and SolidWorks are supported for product model representation, DADS (Dynamic Analysis and Design System) is employed for dynamic simulation of mechanical systems including ground vehicles, and DOT (Design Optimization Tool) is included for a batch mode design optimization. In addition to the commercial tools, a number of software modules have been implemented to support the integration; e.g., interface modules for data retrieval, and model update modules for updating CAD and simulation models in accordance with design changes. Note that in this research, the overall finite difference method has been adopted to support design sensitivity analysis.     

A novel CACD/CAD/CAE integrated design framework for fiber-reinforced plastic parts

This work presents a novel CACD/CAD/CAE integrated framework for design, modeling, and optimization of fiber-reinforced plastic parts, which can greatly enhance the current design practice by realizing partial automation and multi-stage optimization. To support this framework, a new heterogeneous feature model (HFM) has been developed to model the fiber-reinforced objects and to be transferred between engineering modules. To be specific, the CACD (computer-aided conceptual design) module employs the level-set structure and material optimization to produce the initial design with thickness control, and also the initial HFM; the CAD (computer-aided design) module allows manual editing on the HFM to reflect various design intents; then, the injection molding CAE (computer-aided engineering) simulates the manufacturing process, and the response surface method (RSM) is applied to optimize the process parameters of gate location, injection flow rate, mold temperature and melt temperature, to approach the manufactured fiber orientation distribution close to the optimized result produced by the CACD module; besides, the structural analysis CAE module generates the mechanical performance result to support the CACD module, as well as to validate the final design. By applying this framework, the final structural design including the fiber orientation distribution, will perform better in mechanical properties, and consume less matrix and fiber materials; besides, the design maturity can be approached in shorter time. To prove the effectiveness, a plastic gripper design will be comprehensively studied.     

Pen–tablet as a CAD interface alternative

Championed by major industry players, pen–tablet computing is an example of the trend towards ubiquitous computing and natural/intuitive human machine interfaces that offers engineers opportunities to change how they interact with and how useful computers can be for performing engineering tasks, in particular, design tasks. Recognising that engineers starting a new design reach first for pen and paper instead of CAD software, a broad survey on the state of the art relating to sketch driven design was done. This paper summarizes and analyses the survey's review of the roles new computer interaction devices can play in the initial stages of mechanical design where few applications exist to support the engineer. The paper starts by briefly reviewing the role of pen and paper in the design process and then discussing the potential of new interaction devices in mechanical CAD modelling, keeping most of the focus on the pen–tablet interface and the human machine interaction paradigms and modes that it makes possible. Context is provided using summaries of some of the survey findings and accompanied by comments regarding some areas worthy of future research. Comparisons between these new interaction paradigms and current windows, icons, menus and pointers-based (WIMP-based) CAD operation are also included.     

一种基于设计过程的附加式工程数据库系统的研究与设计

针对传统ＣＡＤ系统在设计信息管理上的薄弱环节,提出了一种基于设计过程的附加式工程数据库系统,将工程数据库通过应用程序和数据接口附加在ＣＡＤ系统上,通过二者的有机结合,实现了设计过程中的数据动态实时交换和在线加载,达到了数据共享、重用以及集成化、结构化管理的目的。附加式工程数据库的应用增强了ＣＡＤ功能,提高了设计效率和质量。