| Numerical control machine tool is one of the indispensable equipment in China’s machinery manufacturing industry,which has huge economic and social benefits.With the concept of "Industry 4.0" and the strategic planning of "Made in China 2025",the CNC machine tool manufacturing industry presents the development trend of digitalization,customization and intelligence.Under the traditional mode,the design cycle of CNC machine tools was long and the cost of assembly verification was high.The application of this technology can find the errors in the design and assembly process of CNC machine tools in real time and make modifications to meet the design expectations,reduce the development cost and production cycle of CNC machine tools,and promote the process of manufacturing automation of CNC machine tools.In this paper,CNC machine tools are taken as virtual assembly objects,and key technologies such as three-dimensional modeling,collision detection and human-computer interaction in virtual assembly system are deeply studied.The main research contents are as follows:Firstly,the model building technology of CNC machine tools is studied.According to assembly information and constraints,a bottom-up hierarchical tree of NC machine tool assembly was generated.UG software was used for 1:1 modeling of CNC machine tools and plant equipment by a way that the base parts were constructed and then assembled into the upper-level parts.Considering the limited hardware conditions of the system and the large number of complex and fine models,the number of triangular faces was reduced by modifying the percentage of model vertices by 3DMax,so as to realize the optimization processing of virtual scenes and reduce the system memory consumption.Physical and behavioral modeling was carried out on the model in the virtual scene,and physical attributes such as gravity and acceleration was added to increase the authenticity of the virtual assembly simulation environment.It lays a foundation for realizing a virtual assembly prototype system with a high sense of reality and immersion.Secondly,collision detection is studied based on the mixed layer bounding box algorithm.By studying the theories of five classical bounding boxes,Sphere,AABB,EBB,OBB and kDOP,the hybrid hierarchical bounding box algorithm of Sphere-EBB was proposed.The design process of SE algorithm proposed in this paper was introduced in detail,including the selection of bounding box,the construction of BVH tree,the intersection test of bounding box,and the intersection test of triangular primitives.The advantages of the proposed algorithm in collision detection time and accuracy are proved by virtual assembly simulation experiments.Finally,the design and implementation of the virtual assembly system of CNC machine tools are completed.The requirements of the virtual assembly system were analyzed to determine the overall framework and functional modules of the system development.Aiming at the research of human-computer interaction,animation production,assembly path planning,perspective coordinate transformation and other related technologies,the system function modules were designed,including disassembly animation demonstration,scene roaming,manual assembly,free disassembly,and assessment.System test results show that the system has a good human-computer interaction experience,full of immersion,powerful function,can meet the requirements of CNC machine tool virtual assembly,improve the training efficiency of enterprises or educational institutions. |
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