Research On Virtual Assembly Technique For Pipeline Design

With rapid development of national economics, the applications of pipelines, which are updated almost everyday, are seen almost anywhere, for instance, chemical pipelines, heat pipelines, cable pipelines, oil pipelines, and so on. Pipelines are also used as linking appliances in the interior of rockets and missiles. Virtual assembly (VA) technique is applied in the pipeline design with the following virtual appliances such as data glove, motion tracker and stereo-glasses. A serial of efficient and applicable algorithms are developed to build a pipeline-oriented virtual assembly environment (POVAE), which is intact, high-efficient, and applicable and is applied in a rocket engine.First, the architecture of POVAE is put forward based on the functional requirement analyses of the system. The architecture is mainly composed of four layers, i.e. physical layer, supporting layer, functional layer and data layer, which provide the system with the support of hardware, software, algorithm and data. At the same time, the working flow chart of POVAE is divided into three stages, i.e., the stage of data preprocess, the stage of constructing a pipeline design environment and the stage of pipeline design. In these stages, POVAE takes advantage of immersive characters of virtual environment and the experiences of assembly workers to assemble virtual components and design pipelines.Assembly models of POVAE are built with CAD in the stage of data preprocess. There isn't a data transformation standard between CAD and POVAE, so data can't be transferred directly from CAD to POVAE. Consequently, an approach named Information Decomposition and Transformation Method (IDTM) is proposed to transform data from CAD to POVAE. The IDTM divides the information of CAD assembly models into geometry information, topology information, and assembly information etc., which are transferred to POVAE respectively. The geometry information is transformed through developing a geometry transformation interface (GTI), the topology information and assembly information are transformed by means of database technology.Process-oriented assembly of virtual components in POVAE is realized in the stage of constructing a pipeline design environment. In this stage, an idea of gradual constraint satisfaction based on Quaternion and DOF reduction (GCSBQDR) is put forward, which divides the mates among virtual components into many basic constraints. Decomposition rules for constraints are set up in this stage. And then in order to simplify the mates, three basic constraint satisfaction algorithms and DOF reduction technique are used to add constraints on virtual components step by step. Process-oriented assembly processes are realized with the GCSBQDR plus virtual operation technique based on data glove, which makes the total assembly process natural and high-efficient.Pipeline design in the virtual environment are realized in the stage of pipeline design, where parameterized models of standard pipeline parts, such as pipes, tees, crosses, reducers, elbows and so on are built. A database for standard pipelines is set up. POVAE can design pipelines in virtual environment according to around features with process-oriented pipeline satisfaction algorithm and the controllable technique of pipelines and elbows. Then the information of basic parameters and centerline parameters of pipelines are stored into pipeline database after the pipeline designs are completed, and also these information are used to build new pipelines in CAD system.At last, a virtual reality developing tool is used to develop the POVAE. Rocket engine is used in this stage. Several techniques are applied and verified in this stage, which are IDTM, process-oriented assembly technique and pipeline design technique.