یک سرویس مبتنی بر وب برای بهینه سازی برنامه ریزی عملیات توزیع شده

The advance and pervasive applications of the Web-enabled computations are exerting a profound influence on product design and manufacturing processes, and one of the major technical shifts for product development systems is toward supporting distributed collaboration. A key component for this trend is to develop a service model that enables product development systems to be triggered and manipulated from a remote computer, so as to provide a more flexible manner to share and interoperate the executive codes and processing data. In this paper, a process planning optimization module has been wrapped as a Web-enabled service and deployed in the Internet to support distributed design and manufacturing analysis. The module consists of several optimization approaches, and a Tabu search-based approach, which can optimize the selection of machining resources, determination of set-up plans and sequencing of machining operations to achieve optimal process plans, is elaborated to illustrate the process. The Web-based service has been integrated with a distributed feature-based design system, and the latter can generate design models and re-represent them in an XML representation based on VRML and attributes of features to provide the input of the former. Through effective utilization of the Web and Java technologies, the established service and relevant system can be used by a distributed design team to organize concurrent engineering activities effectively.

Global competition offers sufficient return on investment only to those who can provide innovative products first to the market. In order to develop a complex product with higher quality, less development iterations and more cost competitiveness, an effective practice used in many manufacturing companies in the past decades is to collocate a multi-disciplinary design team, which usually includes research and design engineers, manufacturing engineers and marketing staff, in close physical proximity. Presently, as the global competition and the rapid advances of the Internet technologies, the paradigm of the design activity is changing dramatically, and the structures of design teams for developing products are extended from a hierarchical organization within a company to a distributed organization across companies. Future design systems are moving towards supporting distributed and collaborative activities, in which geographically dispersed designers, systems and resources can be integrated in an Internet/Intranet environment and a virtual design team across the traditional boundaries of physical and time zones can be set up. As one of the most popular Internet tools, the Web aims to provide a light-weight, easy-deployed and platform-independent means for users to search, browse, and retrieve information disseminated and shared remotely. Based on the Web, design models can be dynamically shared and updated in an Internet environment and conveniently accessed and manipulated by remotely located people from the design team, management, marketing, maintenance and customers for efficient design collaboration, design process monitoring, product pre-review and evaluation. Application services in product design, process planning, engineering analysis and simulation, can be conveniently embedded in a Web environment as Application Service Providers (ASPs) for remote invoking and manipulation. Realizing the merits of the Web technology, researchers and developers have been actively exploring and developing Web-based design and manufacturing systems, and the work can be summarized from the following two aspects. 1.1. Web-based visualization systems Web-based visualization systems (Cimmetry Systems Autovue™, www.cimmetry.com; Actify SpinFire™, www.actify.com; Adaptive Media Envision3D™, www.adaptivemedia.com; Autodesk Streamline™, www.autodesk.com/streamline-trial) have been developed to support visualization, annotation and inspection of design models to provide assistance of distributed design and manufacturing activities. These visualization systems are light-weight, easily-deployed and platform-independent, and they can facilitate an on-line team to take on design review, discussion, remark, customer survey to enhance collaborative product design and analysis. In order to deliver and manipulate interactive 3D objects effectively on the Web, some concise formats specially designed for Web applications, such as VRML, X3D (www.web3d.org/x3d), W3D (www.macromedia.com) and MPEG-4, have been launched to represent the geometry of 3D models as visualization-used triangular meshes, trimming lines and some attributes (Web3D Consortium, www.web3d.org; [18], [8], [10] and [24]). VRML is fundamental for the series of the standards to represent geometric elements and scenes, while X3D and MPEG-4 are extended to support XML-based representation and video/audio application in compressed binary formats, respectively. Some formats such as OpenHSF (Hoops™, www.openhsf.org) and XGL/ZGL (Autodesk Streamline™, www.autodesk.com/streamline-trial) are functionally equivalent to VRML in geometric representation while they define data and algorithms for effective 3D streaming transmission over the Internet through data compression, mesh simplification and object prioritizing. The Web-based systems are based on the HTTP communication protocol, and there are two basic means of programming, i.e., server-side programming and client-side programming [18], [8], [10] and [26]. For example, Java Servlet, Microsoft ASP1 and CGI, which belong to the first means, can execute codes at the server-side to generate display information at a Web browser (client), and Java Applet and Microsoft ActiveX, which are examples of the second means, need to download codes from the server and execute them at a Web browser. Considering the large-volume 3D data and frequent requirements for interactive operations, hybrid architectures are mostly designed in which the client-side programming is used to support the establishment of the visualization systems embedded in a Web browser and the server-side programming is to maintain the information communication between clients and a server. As Java programming Application Programming Interfaces (APIs) for light-weight 2D and 3D models (such as VRML models), Java2D and 3D have been popularly used to run in a Web browser for graphics rendering and manipulations. 1.2. Web-based design and manufacturing systems Due to the diversified functions and applications, the reported works in this category have different characteristics and implementation strategies. However, from the system infrastructures and information communication mechanisms perspectives, they share some similar development features and trends. A Web-based system presented by [4] integrates and shares engineering information to support design and manufacturing activities such as domain investigation, functional requirement analysis, and system design and modeling. Functional modules in their system are wrapped and supported by CORBA for communication. A Web-based system integrating product design and process planning developed at the University of California at Berkeley [20], namely the CyberCut system, is based on Java Applet programming to include three primary modules: (1) a Web-based feature-based design tool to model prismatic 2.5D parts using a destructive solid geometry (DSG) approach; (2) a new geometric representation based on the DSG for information exchange between the design and process planning modules; (3) an automated process planning system based on two steps, namely macro planning and micro planning. The Federated Intelligent Product EnviRonment (FIPER) system (FIPER Project, www.fiperproject.com/fiperindex.htm; [1] and [2]) funded by NIST is to develop a new product design and analysis technology. The main objective of this system is to develop a Web-based distributed framework for design analysis and product lifecycle support based on component mechanisms and configurable workflow mechanisms. It can provide open and flexible capabilities to incorporate existing analysis and design tools/methods through Java-based wrapping mechanisms including Java Native Interface (JNI) and the FIPER SDK toolkit. A workflow for a design process can be conveniently organized and configured by users through assembling components in the distributed environment [23] developed the Web-DPR system as an infrastructure to support collaborative design and manufacturing. Based on the Java Remote Method Invocation (RMI) mechanism, agents and an event-based mechanism, the functional modules of the systems can be linked and coordinated effectively [19] developed a new geometric representation named as AREP and a collaborative prototyping system based on this representation to perform real-time geometric modification for components/sub-assemblies in an assembly model [16] proposed a Web-based fixture design system, in which an XML format was designed for the transfer of information and knowledge between functional modules in the distributed environment. In the work of [5], Web service architectures were utilized to establish a new generation of distributed design and manufacturing platform based on XML schemas and a communication protocol Simple Object Access Protocol (SOAP) to provide a neutral data exchange format and effective capabilities in interoperability, integration and Internet accessibility of services. A review on collaborative computer-aided design can be found from [13]. Based on the technical characteristics of the previous works, the following research issues reflect the current development features and trends: • The concepts of services and ASPs are becoming more popular in Web applications. To install application modules in remote servers as services and execute them from Web browsers offer many advantages such as avoiding complicated installations for individual computers, easy upgrading of application modules and lowering the acquisition costs for Small and Medium Enterprise (SMEs) through renting these services. One of the crucial research issues is to propose an adaptable wrapping mechanism for application systems to be used as services on the Web. • Most of the current CAD systems are facilitated to export a proprietary model to a VRML model. However, during the conversion process, the organization and relevant property information based on features, which are relatively important in CAD/CAPP/CAM systems for the high-level aggregations and interpretations of geometric and topological information, is lost. Due to this limitation, most of the Web-based visualization systems cannot effectively support some on-line manipulation operations on features such as selecting a feature or its properties for manipulation, highlighting or hiding a feature, or dynamically attaching attributes to a feature in a design model for evaluation and analysis. Meanwhile, as an emerging standard in the Internet and a system-independent way of representing exchange data, XML is being actively explored to support complex engineering information so as to take advantages of its design features and effective functions in the Internet applications. Therefore, it is imperative to develop an XML-based format that is suitable for Web applications, can represent engineering data based on features, and has strong interoperability and cross-platform capabilities. • In order to facilitate the product design and realization processes on the Web, a visualization-based system and the remote application services need to be integrated. The former can provide a Web-based environment for users to retrieve, view and manipulate a design model for design review, analysis or simulation conveniently. The latter deployed in the Internet can be invoked by users dynamically through the Web to evaluate and optimize the design so as to implement a collaborative concurrent engineering methodology. This paper presents the details of the development of a Web-based process planning service and a relevant system that support the establishment of a distributed design and manufacturing environment. The service can allow distributed users to carry out process planning activities through optimizing the selection of machining resources, determination of set-up plans and sequencing of machining operations of a design model. Four intelligent approaches have been developed to solve this optimization problem, and a Tabu search (TS)-based approach will be described to explain the process. The optimization module has been deployed in the Internet as Java Servlet-based application service. Java Applet, Java2D and Java3D technologies have been utilized to develop a visualization-based manipulation environment of the design models and the optimization results. Through an XML-based data exchange format based on features and VRML, this distributed system can exchange information with a distributed feature-based design system to form an integrated design and manufacturing analysis environment across the Internet.

In this paper, a Web-based process planning optimization service has been developed to support distributed product design and development. A Web-based system based on the service provides a convenient platform for users to view and evaluate a design model effectively through dynamically invoking remote process planning optimization service. A distributed feature-based design system can generate design models in an XML-style feature representation to allow a Web-based system to perform feature-based viewing and manipulation. The main contributions of this work are summarized as follows: (1) By taking advantages of the effective utilizations of the Web and Java technologies, this system is independent of the operating system, scalable and service-oriented. The services located in the Internet can provide an effective manner for a designer to conduct a process planning optimization process to evaluate his design or a design by another designer in a distributed design activity; (2) A new XML–VRML style representation has been proposed to carry out some high-level assembly/feature-based visualization manipulations in the Web-based system. This format incorporates the characteristics of VRML and assemblies/features to support Web applications. The XML–VRML-based information representation enables the system to be effectively adaptable to meet the new development of the Internet technology such as the emerging Web-service technology. The future improvement work for the system includes the following three aspects: (1) In order to enhance the performance of transferring and visualizing complex design models or assemblies, a 3D streaming technology is considered to be integrated into the Web-based system to reduce the bandwidth requirement of using 3D design content and enhance the visualization effect. (2) The current system and services are mainly based on the Java Servlet mechanism. With the development and popularity of some new Internet integration technologies such as the Web service, it is necessary to explore new alternatives to integrate the current functions and functional modules under the new system infrastructure such as XML and the SOAP protocol. (3) The optimization algorithms will be enhanced and improved further. For example, the determination and optimization of the machining parameters for features and machining operations will be studied. Meanwhile, new manufacturing analysis services such as a scheduling service for optimizing the utilization of multiple machining resources for multiple design models at the same time, and an assembly service for organizing collaborative assembly design in the Web, are being investigated and developed.