Shulou(Shulou.com)06/03 Report--

1. 1 system integration technology

In engineering design, the main tool software used by designers in the process of product design is CAD software, and the design of electrical products is inseparable from CAD technology. CAD technology is widely used in the development and design of electrical products. With the help of CAD tools, the efficiency of product development and production in the electrical industry has been greatly improved, which makes the market competitiveness of enterprises have been greatly improved, but at the same time. Some new problems have also emerged. The focus is as follows:

1) with the existence of "information isolated island", the computer-aided design of enterprise application is a local application system oriented to a certain department of the enterprise, which leads to the effective sharing and transmission of information among various departments. it also forms the so-called "information isolated island". All kinds of CAX software of the enterprise produce a large amount of data related to the product, but because the research and development companies of each software are different, the data structure of each system is inconsistent, so it is impossible to manage the product data uniformly.

2) A large amount of data will be produced in the process of product development. if these data are not managed efficiently and orderly, it will cause data redundancy and inconsistency.

3) there are hidden dangers in the security of electronic data, and the data will be mistakenly deleted if the designer does not operate properly, which brings great trouble to the enterprise.

In order to solve the above problems, PDM technology has been introduced into the electrical industry, but the CAD system and PDM system of the electrical industry operate independently, and the staff rely on the traditional way to transmit data, which lengthens the life cycle of electrical products and reduces the market competitiveness of the electrical industry. As a product data management software, PDM products can only be fully integrated with CAD software to replace the backward manual management of data, and effectively manage the drawing paper and the data on the drawing paper designed by designers, so that the PDM system can better meet the needs of enterprises.

PDM system is an information integration platform for enterprise product development. Chengdu needs to use this as an integration platform for the collection of different system information. Through integration, it is convenient to manage the data and documents generated by all kinds of software in the product life cycle, and the information between various computer-aided design systems can be shared. During the design and development of electrical appliances in the electrical industry, To establish an integrated platform for all the information generated by different design systems in the whole life cycle of electrical products.

The integration of the system is to make the interrelated information and systems together, so that the data between different systems can be shared, the resources can be fully shared, and the resources can be managed centrally and efficiently. In PDM, integration combines human, production system and engineering system closely to form a unified whole, which makes the data of the product in the whole life cycle relate to each other and unifies the data, so that the relevant departments of the whole enterprise can have an overall grasp of the product information and improve the product production efficiency of the whole enterprise.

1. 2 CAD and PDM integrated architecture

In the process of integrating CAD system with PDM system, we expect to achieve the following goals: first, we can automatically connect the relevant data generated by the electrical CAD system in the electrical product design in the PDM system, and establish the product structure diagram based on these data, so that the PDM system can manage and control the product design process. Secondly, CAD software needs product structure and parts information in electrical product design, which can be obtained directly from PDM system, so that the data of the two systems can be shared, which avoids the inconsistency between product drawing paper and product data in PDM, and makes the product design process more standardized. These two goals can only be achieved by bi-directional integration between CAD and PDM systems. Obviously, the data communication between CAD system and PDM system is the core of the integration between CAD system and PDM system. The architecture diagram of the integration between the 3D CAD system and the PDM system is shown in figure 4.1. Through the integration framework, the desired goal of users can be achieved, and the data sharing between the two systems can be realized.

Figure the overall framework of 4.1CAD and PDM integration

1. 3 Analytic hierarchy process of integration of CAD and PDM

The main goal of integration is to integrate some resources and applications into a cooperative whole, these resources refer to information technology, applications include computer software and hardware, interfaces and machines, as shown in figure 4.2, it mainly enables the interaction of functions between the integrated application system 1 and application system 2, but also enables information sharing and data transfer between the two systems.

Figure 4.2 basic concepts of integration

According to the depth of integration and the different requirements of users, we can divide the level of integration. The level of integration between CAD system and PDM system can be divided into three modes: application encapsulation mode, interface mode and tight integration mode.

1. 3.1 Application encapsulation mode

In essence, the data related to the product is generated by the application of the software, so the integration of the application realizes the integration of the product data. The purpose of "encapsulating" the external application system is to enable the information generated by different application systems to be shared with each other, and to achieve the goal of unified management of the data generated by each application system. The encapsulation mode enables PDM to put feature data and data files in databases and file cabinets dedicated to storing data and files respectively. It provides a powerful guarantee for the efficient and secure management of the data generated in the application system.

Object-oriented data type is the most important feature of encapsulation, and objects can be divided into two parts: interface part and implementation part. As the only visible part of the object, the interface part is mainly aimed at explaining the operation set of the object; the implementation part is composed of two parts, namely the data part and the process part, and the data part is used to describe the object or analyze its state; the implementation of each action needs to be interpreted by the process part.

Encapsulation refers to encapsulating the properties and operation methods of an object in a class at the same time, when only the external interface is visible, and the operation group can be used to describe this module. to keep the interface of the object and the internal representation of the object independent of each other. This makes the operation visible and hides how the data and operation are implemented in the object, that is, encapsulating the object's properties and operation methods at the same time when defining the object. The principle of information concealment is the principle followed by the encapsulation mode, which is mainly shown in: encapsulation means hiding the internal structure of the object so that the user does not see the internal structure of the object, and the use of the object is accomplished by calling the operation (program).

At the same time, the data internal structure expression of the object type can be affected by different programming, and when it is changed by the programming, any program working on the object type will not be affected. When changing the object type implementation, encapsulation can keep the object type program from being affected. When the CAD application is encapsulated in the PDM system, the CAD system integrated with it can be directly activated in the PDM system.

The application encapsulation mode has two characteristics: on the one hand, the files generated by the application tools can be automatically identified, saved, controlled and managed by the PDM system; on the other hand, the corresponding application tools can be opened to activate the files saved in PDM, and the original files can be edited in the tools that have been started. The application of encapsulation mode is relatively simple, less workload and low degree of automation, which is relatively easy to implement in the process of integration of the two systems, but there are also some shortcomings in the application of encapsulation mode. Encapsulation can not manage the specific data of the file, such as the characteristic attributes of the product, parameters and assembly data.

Therefore, the "encapsulation" of the specific data within the product can not be fully understood. When the data contains product structure information, the product structure configuration module of PDM needs to have a full understanding of the internal structural relationships of the product and master these relationships. As a result, when the product structure information between different application systems needs to be integrated, if the encapsulation mode is still used for integration, it can not meet the needs of integration and integration.

1. 3.2 interface mode

Encapsulation can not realize the integration of some data containing product structure information, so it is necessary to adopt interface mode and tight integration mode to achieve integration.

The assembly tree of the product can usually be generated automatically by three-dimensional software when the product is assembled. There is a certain relationship between the product structure tree in the PDM system and the product assembly tree generated by the CAD system. If this relationship is ignored, and in PDM, the product structure tree is manually edited by the staff, it may make the data inconsistent and may also cause errors such as repeated data input. Through the interface program, the product structure tree in PDM can be automatically generated by the product assembly tree in the CAD system. The CAD system provides rich API functions, which can help the PDM system to obtain the internal structure relationship of the product, thus realizing the automatic generation of the product structure tree of PDM. The updated product structure relationship can be obtained in the automatically generated PDM product structure tree, and after the product structure relationship is updated. The assembly files of CAD may be inconsistent with the new product structure, and the API function will modify and save these CAD files accordingly to ensure that the two are consistent asynchronously.

From the above analysis, it can be concluded that the interface mode is a higher-level integration mode than the encapsulation mode [43]. The interface mode can realize two functions: on the one hand, the product structure relationship is obtained through the interface program, so that the product structure tree of PDM is automatically generated by the assembly tree in the CAD assembly file. On the other hand, the latest product structure relationship can be extracted from the product structure tree of PDM, and the assembly files of CAD which are inconsistent with the product structure tree of PDM can be modified according to the updated product structure relationship, so that the two are asynchronously consistent. In the operation interface, there should be a function menu of PDM system on the interface of CAD system, and a function menu of CAD system on the interface of PDM system. This makes the integration of interface mode much more difficult than that of application encapsulation mode.

There are many shared data models between 3D CAD system and PDM system. Based on the encapsulation mode, according to these shared data models and through the data interface, some data objects of 3D CAD system do not need to be created manually in PDM system, or the data objects needed in 3D CAD system can be called from PDM system.

According to the user's requirements for system data, the interface mode can also be divided into tool interface, straight-through interface and indirect interface.

1. 3.3 tight integration mode

Among the three integration modes, the tight integration mode is the highest level of integration between CAD system and PDM system. This integration mode enables all types of data in CAD and PDM systems to be bidirectionally exchanged and shared. The tight integration mode analyzes in detail the correlation between the graphic data generated during product design in the CAD system and the product structure tree generated in PDM, so that the structural relationship between the product data is unified in the two systems. The assembly relationship of CAD should always be consistent with the product structure tree of PDM. As long as the product structure relationship of either of the two systems changes, it will affect the product structure relationship of the other system. And compared with the other two integration modes, the content shared between systems is also expanded, and data and operational services can also be shared.

Tight integration mode is an ideal integration mode for enterprises and the ultimate goal of integration. When realizing integration with this integration mode, the application system integrated with PDM system becomes an organic part of PDM. This integration mode allows the related services of CAD system and PDM system to be invoked each other to facilitate the execution of related operations, which makes the relationship between the two systems closer and is conducive to the realization of real integration.

To sum up, compared with the other two integration modes of CAD system and PDM system, the tight integration mode is the best integration mode, which can meet the needs of the most users, but it is also the most difficult to achieve. In the design process of integration using this mode, system managers need to have a full understanding of CAD system and PDM system so that the attributes of CAD files can be accurately defined and the most suitable working environment for users can be set. In the process of application, users need to have an accurate understanding of the integration commands. The consistency of the assembly tree of the CAD system and the product structure tree of the PDM system is guaranteed by the system. When designing the tight integration pattern, a shared information model is established in the PDM system and the CAD system. When the data in one system is modified, the two sides can still maintain the consistency of the data.

The implementation of the tight integration mode is more complex. To realize the integration with this mode, it is necessary to obtain the internal data structure of CAD system and PDM system, and to establish a unified structural relationship between the data. The development workload is very large and it is difficult to implement. The real integration with this mode depends on the openness of the application system and the degree of understanding of the internal structure of the two systems.

1. 4 related technologies of integration of CAD and PDM

1. 4.1 API technology

With a large number of applications of CAD system in the electrical industry, the design of almost all electrical products depends on the CAD system. Using 3D CAD to design and develop products will produce a large number of design data, and the source of product structure information of PDM system is these data. The ever-expanding CAD application has accumulated a large amount of design data, which requires the management of PDM. The task of PDM is getting bigger and bigger. The traditional way is to let the staff enter the data one by one in PDM, which will greatly reduce the efficiency, waste a lot of time, and reduce the accuracy. Therefore, it is necessary to change this traditional data entry method. The product information generated by the CAD system can be automatically transmitted to the PDM system, so that the PDM can automatically obtain the product design information from the CAD system, which gives rise to a problem. How to extract the product structure information and basic information from the three-dimensional CAD to the PDM system, this problem must be considered first in the integration. In order to facilitate the needs of users, the three-dimensional CAD software commonly used in enterprises provide customers with relevant API functions.

The API of the operating system provides a way to call the functions of the operating system; the API of the database provides the methods of database connection and data operation. Many large and mature applications also provide their API for external calls to perform the operations required by external programs and return data.

API: application Program Interface (Application Program Interface) is a set of sets used to define programs and protocols. The communication between various product design software depends on API functions. Designers develop applications through the use of API functions, which can reduce programming tasks and improve work efficiency. At the same time, API can also be used as a middleware to share data from different platforms. The method used in the API interface is object-oriented, and users can use different programming languages to program and debug the objects of all functions.

When the CAD system is integrated with the PDM system, the use of the API function is very important. The correct use of the API function will make the integration proceed quickly and smoothly. Generally speaking, a large number of design data and model documents are generated in the product design process, which are often saved in the server database or FTP. The flow direction of the data in the integration process is divided into two types, namely "flow in" or "flow out", which requires that the two-way integration process data can be uploaded or downloaded before uploading the data to the system. Through the correct use of the API function to traverse the assembly tree of the product generated in the CAD assembly module, in order to get the structure of the product and the basic attribute information of the product. After downloading the uploaded data from the system, we also use the corresponding API function to build the product structure tree in the PDM system, so that the assembly model of the product can be updated with the update of the product structure tree of PDM. To sum up, the efficiency of integration will be greatly improved by using API function correctly.

1. 4.2 COM component technology

COM is the English abbreviation of Component Object Model, and its Chinese full name is component object Model. It is a software component structure standard, which was formulated by Microsoft in 1993. Its purpose is to flexibly complete the creation of applications, and the initial goal is to provide support for object linking and embedding (OLE).

One of the functions of COM (component object Model) is to give a standard way to build components, which is actually a way for software components to communicate with each other. The only requirement for any two components is that they run on two interconnected computers, whether or not the two computers run under the same operating system, as long as their respective operating systems can support COM, and no matter which language the component is written in, the two components can communicate with each other. The COM specification is a set of documents that set standards for component architecture and provides a way to write language-independent components that can provide services in the form of object-oriented API. COM has an API called the COM library, which provides component management services that are useful to all customers and components.

The COM interface defines the function of the interface, and the specific implementation of the function is completed in the COM component. A COM component can implement any number of interfaces, which can be achieved through multiple inheritance of abstract base classes that define interfaces or the use of nested classes.

COM not only provides binary network standards for components, but also provides some programming models and defines a set of mechanisms, which can realize the interoperation between software components and support software components technically. COM is a universal model that can be used to build components for any type of application, rather than a special type of application.

Three-dimensional CAD design software So1idworks is developed based on Windows platform. It can provide a large number of API functions, and can use object-based methods to create these interfaces, these objects refer to COM objects. API can show the functions of COM objects, each COM object has its own characteristics, they have their own unique data and methods, which will be hidden after the application program interface. The use of the pointer realizes the access to the COM interface. When the interface pointer of the object is obtained, the interface function of the object can be called to carry out specific operations.

1. 4.3 XML

XML, the extensible markup language, is the abbreviation of Extensible Markup Language, which can enhance the reliability of interaction and cooperation through the network and enhance the operability between them. Based on the technology, it is very convenient for developers to use the network for data representation, processing, data exchange and transmission and so on.

XML came into being in the late 1990s. In February 1998, the W3C organization issued the XML standard. The original purpose of the W3C organization to publish the XML standard is to define a standard for Internet data exchange, which is used to solve the problems of transmission and document exchange between computers. Unlike other languages, XML is not structured, it is a semi-structured language, it contains three elements. They are: document type definition DTD, extensible style language XSL and extensible link language xlink. DTD defines elements and their attributes in XML files, and explains the relationship between elements and their attributes. In order to realize the unified representation of XML document data and the mutual collection of data, we need to rely on namespaces, and the presentation style of XML documents can be defined by the extensible style language XSL, so that the mutual independence between data and data expression can be realized. At present, the simple links on Web will be further extended by the extensible link language xlink. XML can be used as a bridge between a variety of applications to effectively solve the exchange of heterogeneous data.

The advantages of XML in data exchange are as follows:

1) XML has many advantages, such as: its internal content and form of expression are independent of each other, and it also has cross-platform portability, self-description performance is also very good.

2) good structural representation ability: when the data is exchanged, there may be some differences between the source data and the data we finally need (here we call it "target data"). And if the source of the data is not single, there will be multiple data sources, and these different data sources may be made up of different data schemas. Therefore, it is all the more necessary to have a good structural representation ability language to realize data exchange.

3) the ability to express data: the essence of a document is a tree structure. XML consists of nested tagged elements. There are multiple nodes in the tree structure, and these nodes are the elements of XML. The information about an element can be defined by its attributes, and for an element in an XML document, it can have several attributes. The data contained in the entire XML document can be obtained by traversing the tree, and it becomes very convenient to find one or more specified nodes.

4) semantic representation ability: attributes can be used to comprehensively describe a data type. There are many aspects of data attributes, such as name, unit, format, data type and so on. When defining data, the more attributes of elements, the more accurate the definition of data. In order to enhance the semantic representation ability of data, XML can increase the attributes of elements.

5) data can be easily shared among heterogeneous application systems: the flexibility, good expansibility, cross-platform portability and good self-description of XML provide possible conditions for data sharing between heterogeneous application systems.

6) data integration from different sources: structured data may have many sources, which can be combined by using XML, and XML integration between data from back-end databases and other applications can be achieved on a server in the middle tier. At the same time, XML is open and has rich semantic information, and users can use DOM parsing technology to analyze the DTD of XML to obtain the document organization structure, so XML is very suitable to be used as a middle-tier representation of heterogeneous data or an interface for data transmission.

1. 5 summary of this chapter

This chapter mainly introduces the relevant knowledge of the integration of CAD system and PDM system. Firstly, it analyzes the necessity of integration, introduces the level of integration according to the need of integration, and focuses on the analysis of three integration modes in the integration level section. It mainly introduces the concept of three integration modes and their respective advantages and disadvantages. Finally, it introduces the related technologies used for the integration between CAD system and PDM system. This article is from Yuyun sheet Metal Software. For more details, please click: www.plmpdm.cn

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