Research On Virtual Prototyping System And Its Key Technology Based On DAG Scene Graph

Under the circumstances of market competition being increasingly intense, how to enhance speed of product development, reduce cost of product and launch new product in good time into market is a great challenge being faced with enterprises now. The experimentation of prototype of new product is a key process not to overstep in product design cycle. But the fabrication and test of physical prototyping is one of the key problems that gravely affect cycle and cost of product design and manufacture. So, in order to solve the problem virtual prototyping naturally becomes the focus of attention, which it can simulate physical prototyping.Based on analyzing the status quo of research and application of virtual prototyping, this dissertation systematically carries out profound researches on modeling theory, assembly, simulation and integrated with existing CAD tools about virtual prototyping based on PC, because of fall short of virtual prototyping supported by PC and strongly requirement of the potential market. The main research gists are included in as follows:1) Three level structures model for virtual prototyping system based on PC platform and framework on information integrated are presented, which can implement mechanism of human-product interaction and reuse of part geometric model and information communication during product design cycle.2) While the concept of virtual prototyping is defined, a dynamic scene graph based on directed acyclic graph (DAG) for digital product model of virtual prototyping to be represented is presented according to function features and requirements of virtual prototyping to be analyzed in detail. The overall function requirements are generalized in the model structure; therefore, the nodes in the model can dynamically be assembled together and disassembled from it. Also, it is well basis of real time assembly and disassembly for virtual prototyping with the scene graph model.3) Idea of human-product interaction is presented according to features of 2D input and output devices. Mechanism of the human-product interaction is build without virtual reality devices, which real operation on virtual prototyping can be implemented with it. The idea emphasizes the role of human intelligence and visual control ability of human, and forms human-centric design system while technique basis is provided with the idea for tactile interaction.4) The algorithm of recognition and extraction for assembly and geometric characters of part model with theory of spatial vector calculation, which can solvethe problems of real time assembly and real operation with part model.5) A novel motion-simulating algorithm on virtual prototyping is represented. It can directly solve driven-part transform matrixes by spatial vector analysis, and then deviated-angle of the driven-part transform matrixes with constructing a triangle. Eventually, the driven-part transform matrixes are compensated by the deviated-angle. The algorithm is simpler, but high efficiency for operation and easiness for implementation. It is suit to the scene graph models in this dissertation.6) In order to solve the contradiction of accuracy for assembly and motion of product and greatly calculating spending of collision, a grading interference-testing strategy is presented and an algorithm of interference testing based on LOS with probe in local key point.7) By the principles and methods of virtual prototyping above-mentioned, a virtual prototyping prototype system based on PC for widely small -to-medium enterprises(SME) is developed with object-oriented technology. The system proves that the researches on system structure, algorithms, technique methods and data structure in this dissertation are feasible. The functions of human-product interaction, real time assembly and motion simulation are easily implemented without supported by costly virtual reality devices, as well as extended this simulating methods to virtual reality device.