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CHINESE JOURNAL OF MECHANICAL ENGINEERING 106Vol. 20, No. 5, 2006TANYingCollege of Manufacturing Scienceand Engineering,Sichuan University,Chengdu 610065, ChinaCollege of Computer Scienceand Technology,Southwest University for Nationalities,Chengdu 610041, ChinaYIN GuofuHU RuifeiFANG HuiCollege of Manufacturing Scienceand Engineering,Sichuan University,Chengdu 610065, ChinaMODELING METHOD OF 4D INFORMATION MODEL FOR COOPERATIVE DESIGN OF MECHANICAL PRODUCTS*Abstract: The continuous developing features in the design of mechanical procict and based on 3D entity model is aimed at, and the extension of the 4-dimensional model with the process of designing, the knowledge described model on the level of semantic understaJiri3 ar.d summarizing the designing process and the way of discovering knowledge fron: TiLli-imormatiin model are studied. On the basis of designing the broad sensed collaborative system, through discussion of the relationship between the implicit knowledge vi the users and the deigning knowledge as well as commanding all the designing links, takirg advantage of the way ot concluding and deducting in the concept of the designers, the synthetic knowledge unit formed in the dynamic process from the conception design to the last derin is schonvd out, and the knowledge discovered principle in the dynamic designing pross of the mecsiucal products and the key technology in its implementation undsr the milieu of network is brought forward.Key ureitlj; Konr-dLrnf,nsional(4D) Product design Conceptual design Cooperative design Data mining0 INTRODUCTIONNowadays, three-dimensional (3D) model has been widely applied in the design process of mechanical products. For instance, the technology of 3D entity modeling digitized hypothesized prototype, dynamic assembly simulation, and standardized interface, etc, can help designers predict and evaluate their designs and enormously enhance the efficiency in mechanical products designing. However, some deficiencies can not be ignored when designers completely rely on 3D model software to carry on the design. CAD/ CAM software system, as an example, can only describe the model of geometric products itself, such as the definition of 3D geometry, topology, and its characteristics, but fail to describe the process of 3D model formation. Therefore, it cant support the discovery and accumulation of knowledge in the designing process as well. Meanwhile, the system also lacks the encapsulation and integration in the field of knowledge during the process of developing the mechanical products. In addition, it makes little advantage in understanding the designers intention and cant support the function integration in the development of the products and the concurrent design in different areas.In fact, from concept designing to manufacturing and generating final products, it is an interactive dynamic process to carry on the mechanical products design by using CAD system. It is also a process of discovering and solving problems put forward constantly from the conceptual design. Based on these factors, this paper proposes to establish the process of the products with the linkage in its design advancement and based on 3D model foundation, integrate the domain knowledge in the 3D model with its encapsulation in the designing process and thus constitute a complete space with the full information of the lifecycle of the products, namely 4D information model.The purpose of the following passages is to introduce how to discover knowledge in designing process with the assistance of generalized collaborative design platform in a way of data mining based on the idea of 4D information modeling, integrated with the existed 3D modeling technology.Selected from Proceedings of the 7th International Conference on Frontiers of Design and Manufacturing(ICFDM2006). This project is supported by National Natural Science Foundation of China (No. 50275100) and Key Scientific and Technological Projects in Sichuan, China (No. 2006Z01-001-6). Received October 14, 2006; received in revised form May 11, 2007; accepted May 24, 20071 SPACE-TIME CHARACTERISTICS IN DESIGNING PROCESS AND DEFINITION OFTHE4D INFORMATION MODEL IN PRODUCTS4D model technology is a new development of computer science application. Though its research is still at starting stage, its application studies in the construction management have already resulted in great concern both at home and abroad. The theory of 4D model was put forward at first in 1996 by C1FE (Center for Integrated Facility Engineering of Stanford University). Afterwards they have proposed CAD system of 4D, however, this system is also in research as it has not established the whole 4D model in the construction process. In addition, some people, like ZHANG Jianping in Tsinghua University, also devoted themselves to the application research of the 4D model technology in the construction management. At present, there is no research of knowledge discovery by application of the 4D model technology in mechanical product design process. Therefore, it is important in theory and valuable in application to propose the principle and method of knowledge accumulation and discovery in the application of the 4D model technology in the design process of mechanical products, which can provide a more reasonable and optimized design platform.The space-time characteristics of the designers, design groups and design advancement possess are the premises of constructing 4D model in the process of mechanical products design.1.1Space-time characteristics of designers thinkingBecause we live in the 4D space, our consciousness must be dynamically changed and have obvious space-time characteristics. In the course of designing, the designers thinking is a course of dynamic evolution in the process of discovering and solving problems. If the information can be integrated and analyzed in 4D information model by application of data mining, the abstract inspiration and individual experience of designers thus can be turned into valuable materials for later use.1.2Space-time characteristics of the designers cooperativedesignModem enterprises require supports from various external elements in research and development. So the coordination research is not only the one within enterprises but also the one among enterprises. The users, the part suppliers and other1 9 -20 C i a Ac demcJ urnal le r ic u sh e/CHINESE JOURNAL OF MECHANICAL ENGINEERING 107 organizations are playing a very important role in product research and development. If they can fully participate in the product design together with the designers of enterprises, this participation will be helpful to guarantee the consistency of interests and sharing of risk in the course of developing, to assist enterprises in rationalizing resource and design progress, and to reform dynamically the design process.Due to participants being semi-independent and their relatively dispersed geographical position, and the fact that they need massive communications, the technical module used for the collaborative work of the design groups can be sealed in the 4D model, which facilitates participants exchanging, gaining and analyzing information, and thus provides a powerful support for the designing decision-making.1.3 Space-time characteristics of design processIn the process of products design, from the users demand to final forms of the products, there exist a series of design links, which unceasingly reduce abstract degrees. Since the succeeding links are the clarification and extension of the preceding links, the process shows macroscopically a succession of series question and solution activities. If we can collect and analyze the factors which affect each step of policy-making, the 4D r,iodr;l renewal and maintenance for the design will be well supported.Based on the analysis of the above product design process in space and time characteristics, the definition of 4D information model which this article proposes is the realization of the dynamic simulation and the tracking management of the design process, taking products 3D models as the foundation, and the design process as the time coordinate, integrating the product design dynamically in the 4D database, which can be applied in the principle and method of knowledge accumulating and data mining used in the research of the dynamic mechanical products design process.The factors which make up 4D information models should include interaction, restrictive regulation, and operation among information source, process, incident and projects. The models include 3D model database, schedule, 4D model regulation database, and so on (Fig. 1).Fig. I 4D information model structure(1) Production 3D model database: 3D production model can be constituted by all kinds of 3D CAD software in market.(1) Schedule: the timetable of parts forming into components and components assembling products.(3)4D model regulation database: 4D model regulationdatabase is the key link of 3D model transforming into 4D model,including the design concept of products parts, the condition andcriterion of data exchange, the successive relationship of designprocess and various factors restricting design.(4)4D database: 4D database is formed from the 3D productmodel and the design process, depending on 4D regulation in acertain way.In the process of 3D modeling, the first step is to analyze the target product and make certain the major characteristics of product structures and the rational modeling order. The second step is to begin with the basic characteristics such as contact surface and external form and then constitute a model according to the structural characteristics. The third step is to complete all the details and realize a breakthrough from the plane to 3D cubic expression of the product with the accurate digital information acquired. We can express the accurate assembling order, objective assembling relations and motion process of mechanic product, display the emulational mode of process motion and thus enableothers to clearly understand its structural and functional characteristics and more vividly observe the assembling relations of mechanic products through the description of the 3D object and its characteristics in interaction by VRML.The design evolution process can be accurately described through time characteristics and the process of 4D modeling can be dynamically visualized in virtue of 4D regulation. 4D model have provided two-way administration pattern at the same time and users can manipulate the 3D model object in the screen and modify the progress and information of components.Components cant be modified in the traditional 3D models and only the final products can be visualized. In the 4D design, we can visualize the design process of all the parts, components and finished products on the screen. Geometrical information can be clearly displayed in different layers and bugj will appear in all aspects. Through the real-time modification by the computers, the dynamic simulations of the n:echan;cai products, and the overall view of its motion process, we car! hav? the feedback and data modification in time.in tit 4D database, che design data of products can be recorded ir detail, which can be reused for similar products (Fig- 2)-Cjikr ,_*Similar part 1PartiSeekSimilar part 2YNDesignSimilar part n*Fig. 2 Reused designThe design of reuse can shorten the periods and reduce the cost. Through importing the design state and characteristic parameter, if the condition is matched, designer can seek similar components and parts, and add some technical characteristic. If not, the parts can be directly designed.The first step to reuse the design resource is to build a database including key information and make designers easily understand the design outcome and acquire the products design information.2 MODELING METHOD OF 4D INFORMATION MODEL FOR COOPERATIVE DESIGN OF MECHANICAL PRODUCTSIn the product design process, because of subjective or objective reasons in different fields, the factors have been constantly changed such as products 3D models, designing technique, human resources, design tools, fund cost, material and equipment adopted. The dynamic process is corresponding to the time characteristic of 4D information model.Through the collaborative technology in broad sense, 4D model databases not only realize the function of acquiring the information of three-dimensional model of the products, but also real-time control and optimize the design process more effectively. Thus it can guarantee the key data in the design and make the consistency of the data. In addition, the most important thing is that it can develop the implicit knowledge in the design process, design products to most met the demand of users and scheme out a design principle applicable in the development of new products.2.1 Establishment of the design platform for cooperative designIn order to promote new products, meet users various demands as soon as possible and reduce the cost of products, users and component suppliers are required to support designers. By getting involved in the whole design process, they can check out the problems and offer their suggestions so that design programs could be adjusted in time. According to the different participants in the cooperative design, there are three ways as follows.(1) Cooperative design among the enterprises and users. A successful design is to develop products with individualization0 C i a Ac ena 108 -TAN Ying, et al: Modeling method of 4D information model for cooperative design of mechanical productsaccording to different users needs. So, enterprises must fully understand users concrete demand and make the information used in design process of the custom-built products. Communications between users and enterprises could promote their cooperation, establish the optimized 4D model and provide the most satisfacting design products.(2) Cooperative design between enterprises. Since the division of labor becomes more specific nowadays, the manufacture industry had formed a pattern that components are processed at different places and then machine are assembled in one place. The main targets of coordination between enterprises are to assure the components and functional models meet the requirements of design and function of products, and to enhance the producing efficiencies and economic benefit.(2) Cooperative design between every department in enterprises. The advanced information technology platform and optimized organization can promote the unblocked flow of technology and knowledge among enterprise staff, however, the more important one still lies in understanding and setting up the mechanism designed in coordination, promote cooperating on ones own initiative and positive knowledge sharing among the staff.In a word, more and more participants and product projects are involved in coordinate design. The demand of standardization and modularization to die products and production process become higher and highst; 7i;e network technology represented will play a greater and greater role. Through the coordinative designing platform, each positive factor of participating in product designing can be fully aroused.2 J2 Optimization of the design plan in the 4D data model space3D model can only demonstrate the final models of products, but fails to reflect a large amount of useful information of the forming process of the products. Therefore the designers thinking can not be reflected, and furthermore, the concrete information is also unable to be presented, such as jig of handling tool used in the design process. 4D model can offer a large number of initial data and dynamically reflect the whole design process. These advantages have helped participants to discuss, revise and reconstruct the design models. 2.2.1 Constitution of the 4D modelWe can adopt various existed kinds of business software and develop different professional plug-in packages and 4D prototype tools in order to establish 4D model. Technology route is shown in Fig. 3.B%j Hierarchical 3D file formatCommercial tool -i Prototype 4D toolsFig. 3 4D modeling process with prototype tools1. Prototype developed to import VRML files and schedule content and provide basic 4D functionality in an on-line environment1. Internal translator was update for input into Java/4D application1. A kind of 4D systematic model suitable for systematic design, performance and productive potentialities in the development of system(1) Importing the schedule data into Java 4D application. The schedule can be generated by the software such as Primavera and Microsoft Project.(1) Importing the CAD data into Java 4D application. This process includes converting the 3D files with the assistance of software such as Muligen and Wavefront, VRML inner converter, 4D prototype tool, and Java 4D applet.(3)If needed, organizing the CAD data into appropriategroupings.(4) Linking the components to the program activities(4) Assigning the file type for conversion(4) Exporting 4D model to Java 4D applet 4D model based on the above steps has no need toreconstruct the whole model when it is updated. Designers could redivide the modules in the 4D platform, and furthermore, they may selectively produce Java 4D applet data for participants coordinated design through internet. The deficiency of this model is that the data of VFD file are ASCII, which are not favor for subdivisional schedule.2.2.2Updating and maintaining of the 4D modelThe alteration of design plan and schedule brings about therenewal or correction of 4D model. Designers may make a whole or partial adjustment of the 4D model items with computer algorithm to achieve the automation processing, for example, the project and the involved link can be added, deleted and modified.2.2.3Distribution of the 4D model4D models generally are distributed in the Java 4D applet orCAVE formats. In the past, 4D model can only be distributed in jpg format without 4D software, and so that can only be reviewed rather than be transformed. However, by introducing the interactive Java language, now participants of design program can view the 4D model by explorer rather install some software of 4D. In this format of view, the participants can view the motion of 3D model formation (adjust the view according to the demand of users, such as scaling, rotation, varying viewpoints and drawing model). Meanwhile, participants can see the relation between projects in schedule, which provide the convenience for communication, evaluation and forecast.3 KNOWLEDGE ACQUISITION METHOD ON BASIS OF 4D INFORMATION MODELKnowledge assets include explicit knowledge and implicit knowledge. The former is the skill and objective facts that can be spread to others including letters, pictures, sound, etc. And the latter is the skill, judgment and intuition, all of which can be embodied and not easily be described, such as insight, inspiration, vision, experience and so on. As they are subjective, random and fuzzy, they cannot be used effectively. Making advantage of the data mining techniques to discover knowledge assets based on 4D information model, on the one hand, could provide the designer with the information and tools assisting for decision making, overcome the limitation of their experience, and make up for the shortage of the only qualitative knowledge on the books or booklets for design; On the other hand, due to the procession of the data min
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