1. Characteristics of the virtual prototype method
Compared with the traditional design and development method based on physical prototype, the virtual prototype development method has the following characteristics. First, it is a brand-new research and development model. Virtual prototyping technology truly realizes product optimization from a system perspective. It is based on concurrent engineering, which enables rapid analysis and comparison of various design schemes in the conceptual design stage of a product, determination of sensitive parameters that affect performance, and visualization technology to design and predict products. Characteristics and responses under real operating conditions until optimum operating performance is obtained.
Secondly, it has lower R&D cost, shorter R&D cycle and higher product quality. Establishing a digital model of a product through computer technology can overcome the limitations of cost and time conditions, and complete countless virtual experiments that cannot be performed by physical prototypes, so that the optimal solution can be obtained without manufacturing and testing physical prototypes, which not only overcomes cost and time. Conditional constraints, and shorten the development cycle, improve product quality.
Finally? It is an important means to achieve dynamic alliances. The virtual prototype is a digital model, which transmits product information through the network, and has the characteristics of fast transmission and timely feedback, which makes the activities of the dynamic alliance highly parallel.
2. Main steps to build a virtual prototype
The Virtual Reality Lab at the University of Michigan, with funding from Chrysler Automobiles, has conducted research on the process of building a virtual prototype of a car, including how to create a virtual prototype from a CAD model of a product and how to use the virtual prototype in a virtual environment. Human-computer interaction tools, automated algorithms and data formats have also been developed, with the result that the time required to create virtual prototypes has been reduced from weeks to hours.
The main steps to build a virtual prototype are as follows:
(1) Take out the geometric model from the CAD/CAM model.
(2) Tessellation: Use polyhedrons and polygons to approach geometric models.
(3) Simplification: Delete unnecessary details according to different requirements.
(4) Virtual prototype editing: shading, material property rendering, lighting rendering, etc.
(5) Paste feature outlines to better express some details.
(6) Increase the geometric model of the surrounding environment and other elements.
(7) Add manipulation function and performance.
3. An integrated framework to support virtual prototype
The realization of virtual prototype requires the support of simulation tools, the support of domain design tools, and the support of open framework platforms. The integration framework integrates the data management capability of the database, the communication capability of the network and the control capability of the process. It can not only realize the unified management of product data in the distributed environment, but also support the virtual prototype well.
3.1 Structure of an Integration Framework Supporting Virtual Prototype
The integration framework supporting virtual prototype is based on Client/Server structure, and the communication between client and server objects is connected through CORBA-based Client/Server middleware.
Users can use the high-level user services provided by the server through the client user interface, and do not need to care about the underlying implementation structure. Each type of service is composed of multiple agents, and the agents communicate and interoperate in a flexible manner. User services are divided into four categories: data services, integration services, interactive services, and application services.
Data service stores and manages domain data and virtual prototype data, and is responsible for generating virtual prototype data. It uses object-oriented method to model virtual prototype data and uses data language to describe virtual prototype.
Integration services support tool integration and team integration, including shared electronic notepads for communication among people in multidisciplinary design teams, as well as tool integration and packaging mechanisms.
The interactive service provides a 3D virtual prototype environment, supports the visualization and interaction of product data, and creates a sense of immersion for users.
Application services manage relatively static applications that perform specific functions for virtual prototype users. Application services include some tools related to virtual prototype design verification, such as virtual prototype generation tools, virtual simulation tools, and some specific services, such as process management, project management, tool scheduling, concurrent design planning and so on.
In the above structure, the data service is the core and difficulty of realizing the integration framework that supports virtual prototypes. Under these user services, is the underlying support structure, which is invisible to the user. The main purpose of this structure is to support the communication requirements between high-level agents.
3.2 Data Services for Virtual Models
Virtual prototype is a higher-level encapsulation of domain objects, and it includes multiple domains with the product as the core. A complete functional entity of information, providing users with a digital product simulation model. The prototype database stores the multi-domain data collection used by the virtual prototype, including all domain objects, the relationship between the domain objects, and related design data and virtual data. On the one hand, the user interface accepts the user's simulation operation through the simulation interface server, and converts the operation into a simulation request to the virtual prototype; The domain database and the prototype database are respectively placed in multiple servers that are physically distributed. The simulation interface in each client directly accesses the server where the virtual prototype database is located. The server then reports to the server where the virtual prototype database is located in each domain according to the internal domain object management mechanism. The domain object on the server issues a service request, and finally, the result returned by the service is provided to the user interface or the view object The domain database provides data service functions for the virtual prototype mainly in the following four aspects: generation and storage of domain objects; simulation-oriented Data service; data exchange with related fields; data service for virtual data generation. The prototype database is composed of object manager, simulation data server and virtual data generator in terms of data management function. The object manager is responsible for the creation, maintenance and deletion of domain objects and view objects. The simulation data server mainly provides corresponding simulation and data services for the simulation interface through the access to the domain objects according to the user's perception of the interface server. The data generator automatically generates virtual data in the virtual prototype according to certain rules and combined with the design information in the domain database.
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