Research And Development On A Virtual Assembly System Based On One Point Force Feedback

This work mainly studies the haptics-based assembly navigation technology and the one- point force feedback model for virtual mechanical assembly. What’s more, this paper builds a virtual assembly system based on one-point force feedback in the form of CAD add-ins with secondary development technology of CAD, and studies how to achieve the key technologies of virtual assembly in the system. The main contents are summerized as follows:(1)According to the different function requiremnets and the characteristics of actual assembly process, the process of assembly is divided into four stages: grabbing stage, free movement stage, assembly preparation stage and assembly mating stage. Based on these stages, assembly navigation methods have been researched at the assembly preparation stage and the assembly mating stage. In particular, an in-depth study has been conducted on the judgement conditions and force feedback calculation method at assembly preparation stage, and at assembly mating stage,studies the constrained movement navigation technology based on incremental drive.(2)According to the physical constraints of actual assembly and the characteristics of virtual assembly, offset resistance and ongoing resistance in assembly process are firstly studied,and one-point force feedback model is then established. In particular, how fitting parameters of clearance fit, interference fit and transition fit affect the assembly resistance is discussed. For the first time establish a virtual assembly system resistance model according to the mechanical fits.(3)The characteristics and principles of the haptics based virtual assembly system are analyzed, and then the synchronization problem between the haptics rendering and visual rendering is solved with multiple threads. A framework and operational processes of the virtual assembly syestem, which was integrated in CAD system, are designed and implemented. The methods to map the physical haptic workspace to the CAD space,building of the proxy model,and movement simulation and haptics rendering in the system are studied.(4)The feasibility of the virtual assembly system based on one-point force feedback is verified in the case of the gear pump assembly. And then a shaft-sleeve assembly is used as a case study to compare the assembly process in virtual assembly with that in actual assembly.And the pros and cons of the one-point force feedback model are analysed.