Static Stiffness Analysis Of 2UPS-UP+4R Hybrid Mechanism

With the deepening of the research on space mechanism at home and abroad,the basic theory research on series mechanism and parallel mechanism is abundant.Series mechanism has large working space,good flexibility,but relatively small load capacity.Parallel mechanism has high motion precision,large load capacity,but limited working space.The hybrid linkage mechanism,which is compatible with the characteristics of the two types of mechanisms,has the advantages of large bearing capacity,high positioning precision,large stiffness and large working space,provides a new idea for the innovation of space mechanisms.However,due to the relatively complex configuration of hybrid linkage mechanism and the relatively limited application occasions,there are few configurations of hybrid linkage mechanism put into practical application at home and abroad,and there are still many gaps in theoretical research.In this thesis,a new type of hybrid redundant mechanism with2UPS-UP+4R configuration is proposed.The hybrid mechanism is composed of a 3-DOF parallel base and a 4-DOF series claw,which not only meets the requirements of multi-DOF movement of the mechanism,but also has certain advantages in static stiffness characteristics.In this thesis,the existing models and theoretical research status of hybrid linkage mechanism at home and abroad are reviewed,especially the statics and static stiffness research status at home and abroad are deeply understood.The kinematics,statics and static stiffness of the hybrid mechanism are analyzed by using general research methods.In the aspect of kinematics,the kinematic models of series and parallel mechanisms were obtained respectively based on the idea of independent solution of series and parallel structures.Furthermore,the forward solution model of the series part and the inverse solution model of the parallel part were unified into the kinematics solution model of the hybrid mechanism and the workspace morphology of each part was solved.In terms of statics and static stiffness,the generalized external forces and generalized external torques acting on the end of the serial mechanism（the end of the hybrid mechanism）were transferred to the end of the parallel mechanism by force transformation matrix,so that the deformation of the series and parallel parts was superimposed,and the overall static stiffness model of the hybrid mechanism was obtained.In terms of mechanism optimization,particle swarm optimization algorithm was used to optimize the length of a₂ and d₄ rods in series.The optimal value of the rod length is obtained,and then the PSO algorithm is used to optimize the side length of the parallel partially moving platform,and the optimal value of the side length is obtained.The above optimization results provide a theoretical basis for the structural dimension optimization of the hybrid linkage mechanism.Based on the optimization results,finite element analysis software was used to establish the static stiffness finite element model of the hybrid linkage mechanism.The theoretical model and simulation results were compared and the errors were calculated for the hybrid mechanism with typical pose,and the correctness of the stiffness model of the hybrid mechanism was verified.