AtuoCAD环境下对话框的设计开发

本文以齿轮参数化设计中参数输入对话框的开发为例，说明在ＡｕｔｏＣＡＤ Ｒ１２环境下开发实现一个对话框的方法，该方法适用于以ＡｕｔｏＣＡＤ Ｒ１２以上版本为支撑环境的参数化设计应用软件的界面设计。     

AutoCAD环境下对话框的设计开发

本文以齿轮参数化设计中参数输入对话框的开发为例，说明在Ａｕｔｏ－ＣＡＤＲ１２环境下开发实现一个对话框的方法，该方法适用于以Ａｕｔｏ－ＣＡＤＲ１２以上版本为支撑环境的参数化设计应用软件的界面设计。     

在AutoCAD下三维参数化造型系统的实现

本文系统地介绍了在ＡｕｔｏＣＡＤ下,通过使用ＡＲＸ二次开发,实现三维参数化造型的一种方法,对ＡｕｔｏＣＡＤ的实体造型命令进行了重新定义,并提供了对三维参数化实体编辑手段,弥补了ＡｕｔｏＣＡＤ三维造型的可编辑性差、不能参数化造型的弱点,使用户可方便地在ＡｕｔｏＣＡＤ下进行三维造型。     

在AutoCAD下三维参数化造型系统的实现

本文系统地介绍了在ＡｕｔｏＣＡＤ下,通过使用ＡＲＸ二次开发,实现三维参数化造型的一种方法,对ＡｕｔｏＣＡＤ的实体造型命令进行了重新定义,并提供了对三维参数实体编辑手段,弥补了ＡｕｔｏＣＡＤ三维造型的可编辑性差,不能参数化造型的弱点,使用户可方便地在ＡｕｔｏＣＡＤ下进行三维造型。     

基于辅助线滞生法的AutoCADR12参数化设计系统

本文提出了一种在ＡｕｔｏＣＡＤ１２环境下，用Ｃ语言（基于ＡＤＳ）开发二维图形参数化设计的新方法－－辅助线滞生法，解决了辅助线滞生法与ＡＤＳ具体结合中的技术难题；阐述了实元素悬挂在辅助元素上的新思想，实现了尺寸驱动；为用户众多的ＡｕｔｏＣＡＤＲ１２增加了新功能。基于该方法的ＡｕｔｏＣＡＤＲ１２参数化设计系统（ＡｕｔｏＣＡＤＲ１２Ｐａｒａｍｅｔｒｉｃ Ｄｅｓｉｇｎ Ｓｙｓｔｅｍ－ＡＰＤＳ）已用于悬挂灌     

基于AUTOCAD的机器人参数化三维实体造型

提出以广泛使用的非参数化造型系统ＡＵＴＯＣＡＤ进行机器人参数化三维实体造型方法和修改方法,能方便灵活地生成符合需要的机器人及其工作环境的三维实体模型,将其用于机器人离线编程,该方法也适用于以ＡＵＴＯＣＡＤ进行其它开链结构系统的参数化三维实体造型。     

用AutoLisp实现特征造型

特征可以携带并传输大量的几何信息和非几何信息，在实现ＣＡＤ／ＣＡＰＰ／ＣＡＭ一体化技术中具有特殊意义。本文在讨论特征表达和特征建模的基础上，探讨了加工特征库的建立和特征实例化过程在ＡｕｔｏＣＡＤ环境中的具体实现方法，分析了程序设计的几个难点，最后给出零件的特征模型输出结果。     

基于成组技术的面向对象CAD系统的研究

以某模具系列的顶料板设计为例,介绍了用成组技术的复合零件法构造虚拟件,在面向对象ＣＡＤ系统中完成系列化模型设计的方法。较详尽半分析了虚拟件的构造方法与参数化,ＣＡＤ的数据存储方式以及事件驱动机制。并由图形类、数据库类和信息类实现的ＣＡＤ图形与非图形数据的集成。     

基于AutoCAD的参数化特征建模技术

本文介绍了利用ＡｕｔｏＣＡＤ的二次开发工具ＡＲＸ进行零件参数化特征建模的技术和方法,扩展了ＡｕｔｏＣＡＤ参数化造型的性能。     

产品CAD中的参数化建模方法

产品ＣＡＤ中的参数化建模方法电子科技大学ＣＡＥ研究中心杜平安，王豪才用ＣＡＤ方法开发产品时，零件几何模型的建立速度是决定整个产品开发效率的关键。产品开发初期，零件形状和尺寸有一定模糊性，要在装配验证、性能分析和数控编程之后才能确定，这就希望零件模型具...     

Similarity comparison of mechanical parts to reuse existing designs

In actual practice, many new mechanical parts are designed by modifying existing ones. In this way, time and effort can be saved by not having to design parts from scratch. Design time would be further reduced if there were an efficient way to search for existing similar designs. Furthermore, a new part design can be very efficiently generated by modifying the dimensions on the features of the existing part if a part with a similar feature set and the corresponding modeling history can be easily searched from the existing part library.In this paper, a two-step similarity comparison method for B-rep files is proposed. Overall appearances are compared first, and then detailed features are compared. In this way, existing parts with similar feature set in addition to similar overall shape can be identified from the part library. Once the similar part is identified, its modeling history can also be used for parametric modeling if the existing part was designed by a feature-based modeler.     

Vector space model for the generalized parts grouping problem

The vector perturbation approach is introduced for addressing the generalized parts grouping problem, identifying part families for a general set of suppliers, not just a single supplier. This method is driven by the need for flexible and lean supply chain systems. A vector space model is used to represent a set of operation sequences as opposed to the traditional matrix and integer programming models in group technology. Using this approach, we find that we are able to generate part groups from 90% of the available parts, in which all the operation sequences are preserved. This contrasts the traditional methods using which only 66% of the available parts can be grouped. Furthermore, a vector representation of operation sequences provides an intuitive means for discovering the natural structure of the part data. From these results, we conclude that this technique can dramatically improve the effectiveness of the entire supply chain.     

Geometric algorithms for containment analysis of rotational parts

This paper describes a system and underlying algorithms to perform geometric containment analysis to determine if a newly designed rotational part can be manufactured from a part in an existing database of rotational parts. Only material removal of the database part is considered in order to obtain the newly designed part from the database part. The system uses a three-step algorithm to test for containment. The first step analyzes feasibility of containment using bounding cylinders. If the bounding cylinder of the query part is bigger than the part in the database, then the database part cannot contain the query part and it is eliminated from consideration. The second step analyzes feasibility of containment by ignoring off-axis features. Any part that fails to satisfy containment at this stage is eliminated from consideration. The third step analyzes the remaining parts from the database for feasibility of containment by including the off-axis features. Finally, the system rank-orders all the database parts that can contain the query part based on their volume differences with the query part. The system described in this paper can be used by designers and process planners to find an existing part that can be used as a stock to manufacture a newly designed part. This capability is expected to significantly reduce proliferation of parts, to improve manufacturing responsiveness, and to reduce the cost of new products.     

Human-object integrated assembly intention recognition for context-aware human-robot collaborative assembly

Human-robot collaborative (HRC) assembly combines the advantages of robot's operation consistency with human's cognitive ability and adaptivity, which provides an efficient and flexible way for complex assembly tasks. In the process of HRC assembly, the robot needs to understand the operator's intention accurately to assist the collaborative assembly tasks. At present, operator intention recognition considering context information such as assembly objects in a complex environment remains challenging. In this paper, we propose a human-object integrated approach for context-aware assembly intention recognition in the HRC, which integrates the recognition of assembly actions and assembly parts to improve the accuracy of the operator's intention recognition. Specifically, considering the real-time requirements of HRC assembly, spatial-temporal graph convolutional networks (ST-GCN) model based on skeleton features is utilized to recognize the assembly action to reduce unnecessary redundant information. Considering the disorder and occlusion of assembly parts, an improved YOLOX model is proposed to improve the focusing capability of network structure on the assembly parts that are difficult to recognize. Afterwards, taking decelerator assembly tasks as an example, a rule-based reasoning method that contains the recognition information of assembly actions and assembly parts is designed to recognize the current assembly intention. Finally, the feasibility and effectiveness of the proposed approach for recognizing human intentions are verified. The integration of assembly action recognition and assembly part recognition can facilitate the accurate operator's intention recognition in the complex and flexible HRC assembly environment.     

Similarity assessment of 3D mechanical components for design reuse

Duplicate designs consume a significant amount of resources in most new product development. Search of similar parts for a given query part is the key to avoid this problem by facilitating design reuse. Most search algorithms convert the CAD model into a shape signature and compute the similarity between two models according to a measure function of their signatures. However, each algorithm defines the shape signature in a different way, and thus has its own limitations in discriminating 3D parts. This paper proposes a search scheme that successfully complements various shape signatures in similarity assessment of 3D mechanical components. It considers form-feature, topological, and geometric information in component comparison. Such an integrated approach can effectively solve the feature intersection problem, inherited in any feature-based approaches, and capture the user's intent more precisely in the search, which geometry-based methods fail to accomplish. We also develop a set of algorithms that performs the component comparison in a polynomial time. The proposed scheme is implemented in a product design environment consisting of commercial CAD and PDM systems. The result demonstrates the practicality of this work in automatic search of similar mechanical components for design reuse.     

An integrated approach to selective-disassembly sequence planning

De-manufacturing (DM) is defined as a process to disassemble certain parts or components from a product. The parts or components are selected for recycling, reuse, maintenance or disposal. Selective-disassembly as the disassembly of the selected parts is a key process in DM. Allowing a partial and non-procedural disassembly sequence in DM, selective-disassembly aims to minimize the number of removals regardless of assembly indenture levels. It is necessary for selective-disassembly to have an effective and optimal sequence planning in order to reduce tremendous time and cost involved in product DM. The Wave propagation (WP) method, a dominant approach to selective-disassembly sequence planning, focuses on topological disassemblability of parts. It is inefficient to achieve the aim because of two missed considerations: tool accessibility to a fastener in non-procedural and partial disassembly, and batch removability to directly access a part for separation or replacement.This paper presents an integrated approach to selective-disassembly sequence planning. The two examples presented here demonstrate that the approach is efficient and practical for DM. The implemented approach can efficiently generate a feasible and near-optimal sequence plan for selective-disassembly, with ensuring both batch disassembly of components and tool accessibility to fasteners.     

Improving assembly precedence constraint generation by utilizing motion planning and part interaction clusters

In this paper, we present a technique that combines motion planning and part interaction clusters to improve generation of assembly precedence constraints. In particular, this technique automatically finds, and clusters, parts that can mutually affect each other’s accessibility, and hence may impose assembly constraints. This enables the generation of accurate precedence constraints without needing to examine all possible assembly sequences. Given an assembly model, our technique generates potential disassembly layers: spatial clustering is used to generate part sets. Next, motion planning based on rapidly-exploring random trees (RRT) with multiple trees is used to evaluate the interaction between these part sets. Specifically, motion planning is used to determine which part sets can be removed from the assembly. These sets are added to the first disassembly layer and removed from the assembly. Part sets that can be removed from the simplified assembly are then added to the second layer. If the process gets stuck, parts in the parent set are regrouped, and the process continues until all disassembly layers are found. The resulting structure reveals precedence relationships among part sets, which can be used to generate feasible assembly sequences for each part set and the whole assembly. We present theoretical results related to the algorithms developed in the paper. Computational results from tests on a variety of assemblies are presented to illustrate our approach.     

The complexity of oblivious plans for orienting and distinguishing polygonal parts

In the problem ofparts feeding we are given a class of feasible operations for reorienting a part, and we are asked to find a fixed sequence of these operations which is guaranteed to bring the part into a known goal orientation from any possible initial orientation. Goldberg addressed this problem in [2], and showed that, for planar polygonal parts, there is always a sequence of simple operations which can be performed by a simple parallel-jaw gripper, which is guaranteed to orient the part (up to symmetry) without the use of any sensor information; he also conjectured thatO(n) steps are sufficient.In this paper we prove Goldberg's conjecture by explicitly constructing plans of at most2n – 1 steps for orienting polygonal parts in this model. We also give a lower bound on the number of steps required for such plans to show that this upper bound is tight.Finally, we extend these results to the problem ofdistinguishing among a finite set of parts using minimal sensing. Specifically, we assume that we are given a set of known polygonal parts, and a parallel-jaw gripper able to sense the distance between its jaws upon closure. We construct a simple oblivious plan of linear complexity which, when presented with a polygonal part, determines the index of this part.This research was supported in part by the NSF under Grant CCR-9207422, and by a Zumberge Fellowship. A preliminary version of this paper appeared in theProceedings of the Fourth Canadian Conference on Computational Geometry [1].     

ns-2中交换结构的仿真设计和实现

交换结构是高速路由器不可缺少的重要组件,在ns-2中仿真实现交换结构,目标是提供一个具有通用结构和基本功能的交换结构模型.通过队列父类的派生,修改原有的数据结构和分组处理流程,作为标准构件添加到ns-2的构件库中,用户只需在相应的功能函数中添加源代码,就可以开展与交换结构相关的研究工作.仿真结果与理论分析一致,动态跟踪表明开发的交换结构在网络环境中能够准确地转发分组,扩展了ns-2功能进行交换结构网络性能分析.