Research On Digital Virtual Assembly System For Complicated Thermal Structure Parts

In this paper, in order to ensure that the assembly process of irregular thermal structure parts which are thermal shield and metal shell is proceed without contact and collision, and that the assembly has uniform assembly gap, a digital virtual assembly system is studied and developed. Firstly, the involved key techniques are studied, which are shape detection technique, detection data processing technique, model reconstruction technique, virtual assembly simulation technique, interference inspection technique and so on. Then, the system’s corresponding functional modules are developed and the integration of the virtual assembly system is realized. Finally, the developed system is verified that it has the functions of shape detection, data processing, model reconstruction, virtual assembly simulation, interference inspection and so on by test pieces. The system can apply data support for ensuring the safety of real assembly. This study has important theoretical significance and practical application value.The main contents are as follows:(1) The overall development plan of virtual assembly system for irregular thermal structure parts is studied. The assembly form and assembly requirements of thermal shield and metal shell are analyzed and the assembly process is established, then the system’s main functional modules are determined and the overall framework of the system is planned considering the demand of system information management. The system’s development mode which is to make secondary development based on CATIA is determined, and the system development environment is determined comprehensively considering the development cost, difficulty level and the system’s function requirements. The system’s basic development method with VB.NET development tool is studied based on secondary development of CATIA, then system’s main interfaces are designed.(2) The shape data detection of thermal structure parts, processing method and development of this module are studied. According to the shape-size characteristic of the thermal shield and metal shell and the measurement accuracy requirements, the data detection method and measurement equipment calibration method is proposed, then the shape measurement scheme of the thermal shield and metal shell is established. A series of key processing techniques including merging measured point cloud block, removing noise points, slice processing, refinement of slice data, extracting feature points of slice data and sparsely processing of slice data are studied and their corresponding processing algorithms are proposed, then the algorithms are verified by test pieces’measured data. The sliced data storage format is proposed according to the form of reading data in model reconstruction process. The development way of data processing module is studied considering that the data processing work involves a lot of numerical computation and real-time graphics display requirements.(3) The model reconstruction method and development of this module are studied. The method of reading data is studied, then the function of reading data is implemented by programming with VB.NET. The scheme of model reconstruction based on sliced data is established, on this basis the algorithm of curve and surface reconstruction is studied. The hybrid elements modeling method and its basic process in CATIA are further studied, then model reconstruction method is proposed, last the development of model reconstruction module is finished and this module is verified by the test piece’s actual reconstruction effect. Considering the followed requirement of virtual assembly simulation, the construction method of assembly reference elements and the management method of model information are studied.(4) The virtual assembly simulation method and development of this module are studied. According to the requirements that the thermal shield model and metal shell model should be assembled in place accurately and the assembly process should be visual, the assembly method based on coordinate transformation is proposed. The expression form of model posture in virtual assembly environment is defined, and the calculation method of model posture adjustment quantity and position adjustment algorithm is proposed. The development method of virtual assembly simulation module is further studied based on the analysis of product document structure and its contents involved in CATIA assembly environment. The operation process of virtual assembly simulation is established, the model loading method is proposed, and the posture adjustment method and process are studied. The development of the virtual assembly simulation module is finished and is verified by the assembly effect of the thermal shield and metal shell test pieces.(5) The virtual assembly gap and interference analysis method and development of this module are studied. According to the concrete requirement of the gap and interference analysis for the thermal shield and metal shell, the method of realizing gap and interference analysis by making secondary development based on DMU space analysis module, DMU navigator module and other modules of CATIA is proposed. Then the concrete module development plan is established, the analysis algorithm and development steps are proposed. Finally the development of gap and interference analysis module is implemented and is verified by test pieces’ actual running effect.