Figure 2 Overall framework of the design quality assurance system in a virtual environment
The current CAD system provides a powerful part-level detailed design capability. The designer first designs the detailed structure of the part, and then completes the assembly design of the product according to the assembly relationship between the specified parts. This bottom-up design process is not In line with people's design thinking, the design results can not guarantee the function specified by the designer. To this end, the design quality assurance system must support the assembly-level design, the so-called top-down design process. The Design Quality Assurance System (DQAS) we designed is based on this theory, as shown in Figure 3.
The input of the whole system is the user's demand, and the output is the product design result, which is in line with people's design ideas. The whole system is built on the design knowledge base (including geometry library, technology library, function library and management library) and design analysis knowledge base (including feature process library, manufacturability evaluation knowledge base, assembleability evaluation knowledge base and optimization evaluation analysis library). ) on the basis of.
Figure 3 Design process diagram of design quality assurance system in virtual environment
2 Key technologies for design quality assurance in virtual environments
Establishment of virtual design quality assurance environment
According to the interactive nature of virtual reality (VR), it can be divided into different types. Currently, there are three kinds of commonly used, namely desktop virtual reality, virtual reality and enhanced virtual reality. Depending on the design and manufacturing, design quality assurance requires a desktop virtual reality environment that uses a personal computer and workstation to generate simulations in which the designer uses various software for design, evaluation, and simulation. The establishment of the simulation environment is the core content of the desktop virtual environment technology. Because object-oriented simulation breaks through the concept of traditional simulation in theory, its concept of analyzing, designing and implementing the system is very consistent with the natural way of thinking that people understand the objective world, thus enhancing the intuitiveness and comprehensibility of simulation research. Object-oriented simulation is inherently scalable and reusable, providing an extremely convenient means of simulating large-scale, complex systems. In addition, object-oriented simulation is easy to integrate with computer graphics, artificial intelligence/expert systems, and management decision science. Therefore, object-oriented simulation technology provides favorable technical support for the establishment of virtual design quality assurance environment.
Database in virtual design quality assurance environment
The virtual design quality assurance system consists of many different functional modules. Due to the complex structure of the system, the data exchange volume and application frequency are very high. Different functional modules have different data organization and management requirements, and are management virtual design quality assurance systems. A large amount of data in it is necessary to build a database. The object-oriented database formed by the combination of object-oriented technology and database technology can not only provide similar functions to traditional databases, such as persistent storage of data, concurrency control, transaction management, recovery, query, etc., but also provide some suitable for engineering applications. Advanced features and features, such as data abstraction and encapsulation, powerful information modeling capabilities, object representation and combination level polymorphism, scalability, and more. With the gradual improvement and promulgation of the PDES/STEP standard, object-oriented databases supporting PDES/STEP product/process modeling will become an important support for database management in virtual design quality assurance environments. The database under the virtual design quality assurance environment includes two comprehensive libraries: design knowledge base and design analysis knowledge base. The design knowledge base includes geometric library, technical library, function library and management library. The design analysis knowledge base includes feature process library. A manufacturing evaluation knowledge base, an assemblability evaluation knowledge base, and an optimization evaluation analysis library.
Programming and integration of various design analysis software under virtual design quality assurance environment
It can be seen from the framework of the virtual design quality assurance system that the design process includes the design, analysis and simulation process. The whole process requires the support of various design, analysis and simulation software. The various software modules are independent of each Other and pass each other. The interface communicates. The current object-oriented programming (OOP) approach decomposes a software system into a series of logical components that represent objects, each of which is a collection of data and processes. Data represents the state of the object, and the process represents the behavior of the object. Only the process owned by the object can access and change its own data. These features help to create a model that is closer to the real world and execute the object-oriented program through the delivery of the message. To change the state of the object. Therefore, the object-oriented programming tool is an ideal tool for programming and integrating various design analysis software under the virtual design quality assurance environment.
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