Research On Assembly Design Oriented Semantic Modeling And Integrated Simulation Technology

As an important part of the product design process, assembly design determines the relative positional relationship between parts and the corresponding assembly process. To ensure the feasibility of the assembly design, it usually takes multiple iterations. Normally, to modify an assembly design, parts and assembly relationships have to be modified in CAD software before they are imported into the virtual environment(VE) to be verified. The time-consuming data transferring and human-computer interaction can significantly delay the design process. After the assembly design, the model has to be rebuilt in a different environment to perform kinemics analyses, which contains lots of redundant working and could further delay the design process. Current virtual assembly systems only supports the verification of determined assembly relationships, therefore cannot meet the demand of design-simulation integration.To solve this problem, an integrated assembly design method is presented in this research, which enables assembly design, assembly process simulation as well as kinemics simulation in a unified virtual environment. Information can be automatically reused in different phases and simulations, which greatly reduces the work load and promote the design process. The work conducted in this research is listed below:Firstly, to support the assembly process and kinematic simulation, a semantic part modeling method has been proposed. The semantic description contains both assembly features and physical properties of one part. Based on the semantic description method, a unified part definition scheme is proposed based on the STEP format of the model. All semantic descriptions are exported as XML file to enhance its usability and flexibility.Secondly, assembly process simulation based on dynamic assembly relationship creation method have been proposed. The method mainly relies on semantic reasoning to achieve the determination of the assembly objectives, the reasoning of the assembly pose, the building, solving and guiding of the geometry constraint, the generation and modification of assembly relationship. The method is able to simulate the whole assembly process from importing parts with undetermined relationships to forming entire assembled product under the virtual environments.Thirdly, the thesis proposed the kinematic simulation method of the assembled product under virtual environment. Automating generation method of concrete rigid bodies and kinematic pairs is proposed. Using Bullet physics engine, a physical simulation scene is built, where real-time kinematic solving and displaying is performed, realizing the real-time verification of a new product on kinematic properties and motion space.Finally, a prototype system named “Virtual Engineering Simulation Platform-Sematic Assembly & Motion Simulation(VESP-SAMS)” is developed based on the above methods. The system has been validated on an excavator product, which demonstrates the methods proposed in this thesis are feasible and correct.