Shulou(Shulou.com)06/02 Report--

Taking the sheet metal unfolding design system as the research object, the operation mode of ASP and the related theory of distributed collaborative design are studied. With. NET platform is the development environment, and the development method of sheet metal unfolding design system is expounded from the aspects of system infrastructure, related enabling technology and so on. The research of this project will promote the evolution of CAD system structure.

1 Overview

ASP (Application Service Provider) refers to the company that configures, leases and manages business applications on Internet to provide application services for commercial enterprises or individual customers. Users entrust business-related applications to service providers to ensure the smooth operation of these services, responsible for the establishment, maintenance and upgrade of applications, management of application systems, and so on. At present, China's ASP enterprises are still in the initial stage, and the types and scale of customers are mainly large customers, mainly providing domain name registration, host hosting, office automation, customer relationship management and other services, of which only 5.88% can provide CAD, PDM and other services, and less attention can be paid to the technical services needed by enterprises.

Distributed collaborative design refers to the collaboration between design teams in different locations, which involves a series of problems such as collaborative working environment, distributed database management, data transmission and so on. The main task of the distributed collaborative design system is to show its design process to other design members in the network environment, and designers can express their opinions and discuss the design from time to time.

The resources of small and medium-sized enterprises in design capability, software development and IT technicians are very limited, and CAD of ASP mode of distributed collaborative design of mechanical products is very suitable for them. Enterprises or individual customers do business in a simpler and more secure way, which is undoubtedly a more flexible and progressive new model for ASP and CAD software application development.

Distributed Collaborative Design based on 2ASP Model

The characteristics of 2.1ASP mode

In ASP mode, users can carry out various services as long as they guarantee the data transmission speed with a certain network bandwidth and pay the corresponding fees. The main features of ASP mode are:

(1) all services are performed through the network. All kinds of application software of ASP mode are distributed applications based on Web.

(2) the ASP application service platform is targeted. It is generally designed to complete a specific business according to the needs of enterprise customers, and provides a favorable environment for completing and setting up such business.

(3) the distributed collaborative design platform based on ASP mode has the feature of resource integration. On the application service platform, users can not only deal with normal business requirements, but also find and use design-related information resources, such as industry product information and various standards, within the scope of user permission.

(4) ASP shall update, upgrade and maintain the application according to the customer's needs, configure and expand the application software, and provide solutions and training.

2. 2 key technologies of distributed collaborative design

Distributed collaborative product design involves customers, designers, manufacturers and suppliers, which is reflected in the interaction between the designer and the design environment. Design can be regarded as an activity, which is the collaborative design process through the interaction between the designer and the shared environment. In the distributed collaborative design system, the following basic problems should be properly considered and dealt with.

2. 2. 1 network engineering database

Network database is the key to information storage and exchange in the process of product collaborative design. There are usually the following solutions to realize the connection between Web server and database server and to access the network database: CGI, ISAPI, NSAPI, ADO and Java. At present, Web applications developed on .NET platform usually use ADO.NET method to access the database, which simplifies the database operation, programmers can access data through the program, reduces some tedious configuration process, and improves the running efficiency of the program.

2. 2. 2 conflict detection and resolution

In the process of mechanical design, constraints are a large number of interdependent and mutually restricted relationships that need to be dealt with. Conflict is the different design requirements of different designers for the same object. Collaborative design is the process of coordinating constraints and resolving conflicts. Figure 1 shows the conflict resolution process for collaborative design of mechanical products.

Fig. 1 conflict resolution process of collaborative design of mechanical products

There are two kinds of conflict coordination strategies: static coordination and dynamic coordination. Static coordination is to reduce or avoid conflicts by reasonably coordinating design tasks and sharing information before conflicts occur. Dynamic coordination is when the conflict occurs, the conflict is found through conflict detection, and the conflict is resolved by the conflict coordination tool. If the conflict still can not be effectively adjusted, manual coordination is needed to resolve the conflict. In addition, in the .NET platform, there are security and validation controls and related mechanisms to control conflicts before they occur.

2. 2. 3 remote operation technology

Remote operation in distributed collaborative design can be implemented in the following ways: COM / DCOM, CORBA / Java / JavaScript, ASP / Script, ASP.NET / high-level programming languages (VB.NET, VC++.NET and C #, etc.). Among them, the fourth method is a new method and means to develop Web applications and Web services. For CAD, CAM and other server application software, we can refer to its encapsulated class library in the program, directly call its class library and interface functions, and remotely call the server application software through ASP.NET and VB.NET programming, so as to achieve the purpose of application sharing.

2. 2. 4 distributed collaboration methods and tools

Distributed collaboration mainly includes Email, text conversation, voice conversation, video communication, shared whiteboard and application programs. There are many commonly used collaborative tool software, such as Microsoft Net Meeting, Netscape Cool Talk, Web Phone and so on. All of these software can perform remote call, voice communication and video functions on the Internet. This paper mainly uses Net Meeting and its development tool RtcApiSdk, and users can download API functions and interfaces on Microsoft website.

3. Application and implementation of ASP pattern

3. 1 system function

Taking the collaborative design system of sheet metal unfolding based on Web as the object, the application of ASP pattern is discussed. The collaborative design of sheet metal unfolding is based on the features of sheet metal parts, that is, according to the features of sheet metal parts commonly used in sheet metal processing, such as tees, elbows and heads, the collaborative design of sheet metal deployment is carried out by using parameters to provide technical basis for layout, cutting and processing of sheet metal workers.

ASP service process is essentially a process of information transmission and processing. The customer first puts forward a demand to the ASP service center, which can be sheet metal order or production information, product development or other services. Requirements after login, conversion to form a project, into the project management. According to the requirements of the project, the service center retrieves and invokes the corresponding resources, and completes the relevant requirements processing through the ASP service center. The sheet metal unfold design service process of the ASP pattern is shown in figure 2.

Figure 2 ASP pattern sheet metal unfolding design service flow

The basic functions of the sheet metal unfolding collaborative design system based on ASP mode are mainly embodied in four aspects: sheet metal unfolding design, data management, conflict processing mechanism and collaborative mode.

Sheet metal unfolding design is the most important service of the system. When the user puts forward the demand, the ASP service center returns the corresponding deployment design form (Web page) according to the user request, and the user selects the design object, inputs the corresponding parameters and performs the deployment calculation. Finally, the system draws with the calculation results, and the user can download the deployment data and graphics file.

Data management mainly manages sheet metal unfolding calculation results, graphics, customer information and other resources. When users request sheet metal deployment design service, the system requires users to enter their customer information to determine their rights to use and manage the system; at the same time, users are required to enter the parameters of deployment calculation, which will produce a large amount of result data. All this data information needs to be stored and managed in the database. How to manage and use these data and information effectively is the key to whether the system can be implemented or not.

Conflict handling mainly refers to how to effectively deal with and coordinate the use of the system services by users in the case of multiple users. For example, when different designers unfold the same sheet metal object, the system should be able to deal with the conflicts in the process of operation.

Collaborative mode refers to various tools, such as FTP, Email, electronic (audio and video) conference, etc., which provide synchronous and asynchronous cooperation for the exchange of information between users during design communication, and record the data generated in the process of design and communication, so as to achieve the purpose of project document sharing, network resource sharing and collaborative design.

In addition, the sheet metal remote design system of ASP mode can consider to realize remote collaborative manufacturing and monitoring through Internet and local area network. Therefore, the design results can be converted into numerical control code and sent to remote NC machine tools to realize remote machining. Similarly, the processing information sent from the production site can also be accepted, the machining process can be monitored remotely, and the problems in the machining can be solved in time.

3. 2 system structure

According to the service process and function analysis of the sheet metal deployment collaborative design system of ASP pattern, this paper puts forward the architecture shown in figure 3.

Fig. 3 structure of sheet metal unfolding design system with ASP pattern

The sheet metal unfolding design system of ASP mode adopts three-layer B / S structure, namely customer layer / application layer / data layer. Users carry out all kinds of business through browsers on the client side. In addition to installing browser (Internet Explorer or Netscape) software on the client side, they generally also install corresponding controls, plug-ins, multimedia, file transfer and Email software. Most of the application software and service management software are installed on ASP's W eb server. The data layer accesses and manages the results of user operations, including computational data and graphical data, during ASP services. At the same time, the data layer is also the distribution center of all kinds of resources and information in the ASP data center to ensure the smooth, correct and smooth implementation of various ASP services. Therefore, the Web server in the ASP application layer and the database server in the data layer usually run in parallel with multiple servers.

The sheet metal unfolding system of ASP mode uses HTTP and SOAP (Simple Object Access Protoc01) protocol based on Internet / Intranet to communicate. SOAP belongs to the service invocation protocol and is the infrastructure of service interaction in Web service architecture. The data in the SOAP information is completely in XML format, and each processing node can easily understand the semantic information conveyed by the SOAP message, and it can solve the firewall problem smoothly.

In the process of product collaborative design, the data must be exchanged, so the data bus is used to communicate in the sheet metal unfolding design system. The system communicates with the outside through the data bus, and connects with other application systems through it, in order to achieve a wider range of system applications.

3. 3 system design and implementation

3. 3. 1 remote sheet metal unfolding design system

The sheet metal unfolding application system of ASP mode is based on .NET platform and is realized by using VB .NET, ASP .NET, SQLServer2000 database, MDT6 ActiveX Automation, related plug-ins, controls and video tools. The running interface of the sheet metal unfolding design system of ASP pattern is shown in figure 4.

Fig. 4 Collaborative Design of sheet Metal deployment in ASP pattern

The designer first registers and logs in to the system under the guidance of the system, and then puts forward a request for sheet metal deployment design to the ASP service center, and the ASP service center returns the sheet metal design main interface shown in figure 4. After selecting a certain kind of sheet metal design object, the designer is prompted to input the corresponding unfolding design parameters, and the designer can complete the sheet metal unfolding calculation, drawing and generating solid model under the guidance of the system. In addition, the designer can also store and process the input / output parameters of sheet metal design and CAD graphics files.

When designers collaborate, they need to share, collaborate and annotate various design mediums. Designers can use pictures, voice, text, CAD solid models and videos to record and communicate with each other. When using Net Meeting to organize collaborative design, designers can cooperate in real time through remote call. When remote response and security authentication are completed, collaborative design can be carried out among designers.

The design task can be divided in the system workflow and transferred to each called designer using the file transfer function. Each designer uses various applications provided by ASP to start the design of sheet metal parts in their own sub-tasks. Through video and audio devices, multimedia information can be transmitted to all designers involved in collaborative work in real time. If there is no video and audio equipment, they can only receive multimedia messages from other designers, or participate in collaborative design through text messages.

In addition, designers can share their own computer screens or applications (such as IE, etc.), so that other designers can see their own operations in real time, can also use shared whiteboards to express designers' design intentions synchronously, and can also convey and express design intentions and experiences through e-mail subsystems or design messages, which can greatly improve the efficiency of online design.

3. 3. 2 system application logic and data access

The system presentation layer is designed and run based on ASP .NET and .NET Framework. Developers only need to do simple business logic programming, while the ASP .NET infrastructure is responsible for delivering services through SOAP. Web form is based on the server-side dynamic page technology, the server-side according to the client request and submitted information, dynamically generate general HTML pages independent of the client browser type.

At the same time, Web forms provide a more structured way to separate application code from user interface content, so that ASP .NET web pages can be dynamically compiled into controlled classes to improve the performance of application services. In the data layer, access to the database is completed by using ADO .NET. ADO .NET contains a number of classes that programmers use to obtain data access services. To separate database connections from access, ADO .NET uses D ataSet and D ataProvider objects to provide strong support for database operations.

In the sheet metal unfolding design of ASP mode, SQL Server is used as the database server, which mainly manages and stores all kinds of data information in the system, including user information, sheet metal design input parameters, output results, unfolding engineering documents, solid models, common standard information, manual materials, industry information, customer messages and so on. When the user requests drawing, the ADO. Net technology is applied to make the system read the sheet metal unfolding calculation parameters and results from the database. Through VB. Net programming, the ActiveX Automation library function and interface of MDT are called to activate the MDT software on the ASP service center server to draw the unfold drawing and three-dimensional solid model of the sheet metal parts respectively. Sheet metal unfold drawings and 3D solid models are saved in different file formats in the database server and share data with other applications through the system data bus. Users can browse sheet metal unfold drawings and 3D solid models through a browser, as well as download calculation data and drawing files.

3. 3. 3 conflict coordination

The sheet metal unfolding design of ASP pattern is a distributed design system based on Web, which ensures not only the correct and smooth design of a single user, but also the needs of multi-users. Generally, in the case of a single user, the system is stable, but when multiple designers put forward different requirements for the same object, design conflicts may occur.

. The NET framework provides security and verification controls and related mechanisms, and the record values corresponding to each field in the database definition also have corresponding data type, range and other restrictions. When the user's input or operation does not meet the system requirements, the system will automatically catch the error and prompt the user for the correct operation. At the same time, it also makes a comprehensive consideration in the system data management, and establishes a separate instance for the user according to the authority and type of the user logging in and registering the system, so the system provides the corresponding knowledge rule management and constrains each user instance. so that the operational data are stored separately and do not affect each other. Because the .NET Framework supports the compilation and debugging functions of high-level languages, we can use the support provided by the Exception class of the .NET Framework to find coordination and solutions for dynamic conflicts that the system may not take into account.

3. 3. 4 Application of various enabling tools

Generally speaking, CAD graphics files cannot be directly displayed and controlled by Web browsers, but the corresponding plug-ins can be used or CAD files can be converted into neutral file formats that can be recognized by browsers. The main purpose of using plug-ins is to enable browsers to access CAD files directly. The Volo View Express plug-in enables users to view, zoom, rotate, download and print DWG, DWF, DXF and other graphic files using the browser. In addition, because the system calls the MD T6 automation server to realize solid modeling, it is necessary to install the MDT 6 object enabler on the client side to display the MDT solid model in the browser using Volo View Express.

Both Volo View Express and MDT6 object enabler software are free and available for download on Autodesk's website.

The data exchange between different CAD systems is to convert MDT format files into standard data exchange file formats. The main graphic file standards for data exchange on microcomputers and workstations are DXF, IGES, STEP and so on. Recently, Autodesk emphasizes using binary DWG and DWF format on the network as its data transmission standard, but the formats of both are not disclosed, so it is difficult to be used by other CAD systems. Yuyun website: www.bjmes.cn

Online collaboration tool is a Net Meeting tool using Microsoft. Users can download the software and its corresponding development package files (API and help files) free of charge on the Microsoft website. The software is used to carry out remote call and voice interaction in the local area network, and together with the corresponding Web controls to realize the functions of sharing white server and application program, voice and video communication, text conversation, file transfer and e-mail in the system. Figure 4 shows the collaborative design process using the software.

4 Summary

Distributed collaborative design of mechanical products based on ASP mode is a new type of CAD mode, which finds an effective way of demand and service for both users and CAD developers. Taking the sheet metal unfolding design as the object, this paper describes the design process and related enabling technology of the system in detail by using the relevant theories of ASP and distributed collaborative design. The design of the system has a certain theoretical and practical reference value for the development direction of CAD technology and the establishment of a regional distributed collaborative design platform.

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