Study On Multi-User Cooperation Virtual Assembly Environment Modeling And Display Model Simplification

Cooperative designing is the inevitable trend in the modern product designing. However, there would be the interference phenomena among the parts designed by different designers. Therefore the pre-assembly testing is very important before manufacture. Usually the distance between different designers is very far. Designers always require keeping secret information of the part when sharing his product with the others. Different designers may use different software. All those factors make the pre-assembly testing very difficult. However, the cooperative virtual assembly system offers the opportunity for the designers who are at the different places to virtual assembly operation in real time. Different designers can use the system to do the pre-assembly testing through the internet, which could guarantees the designing accuracy, shortens the designing periods, and improves the product's market competitiveness.The subject originated form Key Item of S&T Committee of Shanghai City: Distribute Collaborative Virtual Assembly Environment (DCVAE) Development. The study of my paper is mainly focused on the product date layer and management service layer of the DCVAE system.At present, most virtual reality systems'product information is from the CAD system. Through the second development of the CAD system, we can get a neutral file about the product information as the original file for the virtual assembly system. However, the method about date transform between the virtual reality and CAD system is mainly based on one part. When faced to the complicated product, such as the automobile, it's totally parts number reaches about 20000, the virtual reality should based on the component which is build up by the parts. A four-level product presentation is put forward in the paper, which contains display information, logic information, collision test information, and components information. The new product presentation could support the interactive component operation while faced to the complicated product.Apply the Role Based Access Control to the user management of the cooperative virtual assembly system. Corresponding to the basic concept about the RBAC modeling, analyze the users, the roles and permissions of the cooperative virtual assembly system. The core idea of the modeling is that giving different user different permission through the role. The method takes the user away form product resource which could improve the safety of resource visiting, and simplification the user-permission setting.Put forward a constraint management mechanism about the edition management between the designers and products data, which was based on the character of the product edition in the processing of the product designing. The method could well maintain the product consistency and support the product historical recall.Aiming to the special requirement about the product information of the cooperative virtual assembly system: share but protect the secret information about the product, an arithmetic of simplification the display modeling which based on the assembly feature was put forward. The arithmetic was divided into two steps: firstly, through the second development of the CAD system, getting the information about the box of the assembly feature; secondly, simplify the other part of STL file which is out of the box. The simplification arithmetic was developed form the Garland's quadric error arithmeticThrough the characteristic of the modern automobile designing, a virtual assembly evaluation processing was built up. The DCVAE system has been applied into the cooperative company's new van development processing. And the result shows that product date layer and user date layer which were developed based on the study of this paper could well support the automobile's cooperative virtual assembly operation.