Research And Implementation Of Assembly Path Automatic Planning In Virtual Assembly

In the new product design and manufacturing process,product assembly is always an important part in the product development cycle.Therefore,assembly has also become one of the most important factors that affect product development cycle,product development cost and time.However,in the traditional assembly process planning,the assembly process depends heavily on the experience knowledge of the assembly process workers,which is not only inefficient,but also has high error rate,and it is also difficult to plan the best assembly process plan.Although with the rapid development of computer technology,the application of computer aided assembly planning to ease this problem to a certain extent,but the research focus in assembly modeling,assembly sequence planning,and automatic planning of assembly path has little research.Therefore,on the UG software platform,the realization mechanism of assembly path automatic planning in virtual assembly is studied in detail.Around this topic,the following aspects of research were carried out:(1)Research on assembly path planning based on improved A* algorithmOn the basis of summarizing the functions and relationships of each module of UG/OPEN two development tools,the basic framework of UG two development is expounded.According to the assembly concepts and terminology in UG assembly environment,an assembly information model for automatic assembly path planning is constructed.On the basis of the detailed analysis of the hierarchical assembly path planning,the modeling and calculation of the planning space are deeply studied.The basic method of relation between starting point and starting grid is described.The influence of the different selection of neighborhood grid on the assembly path planning is compared and analyzed.The selection of some parameters in the A* algorithm,such as heuristics and search step length,is analyzed and explained in detail.Finally,the shortcomings of the traditional A* algorithm in the assembly path planning are illustrated,and the corresponding improvement algorithms are proposed.(2)Research on collision detection algorithm based on AABB bounding boxThe performance differences of AABB bounding box,OBB bounding box,Sphere bounding box and k-Dops bounding box in computation volume,memory volume,tightness and collision detection complexity are compared and analyzed.AABB bounding box is selected as the cause of collision detection.The basic method of building and updating the hierarchy bounding box in UG assembly environment is explained,and the basic process of collision detection based on AABB bounding box is analyzed.The basic flow of each API function call is analyzed in detail when the collision detection of the UG’s own interference module is called.A collision detection algorithm combining coarse and fine phase is constructed.(3)Simulation of assembly animation in NX environmentOn the basis of the implementation mechanism of assembly animation simulation,the description of the position and posture of components in the assembly space and the related knowledge of position and position transformation are deeply studied.The position and attitude transformation matrix corresponding to the change of the state of the arbitrary position of the space is derived,and the relationship between the position and posture transformation in different spaces is analyzed in detail.Finally,the assembly path automatic planning system based on UG software platform is built,and the upgrading of assembly process planning digitalization level has been explored and explored.