Design And Analysis Of Five Axis Hybrid Machine Tool Based On 2RPU/UPR Parallel Mechanism

Based on the 2RPU/UPR parallel mechanism,research group proposed a new kind of(2RPU/UPR+R)+P five degree of freedom hybrid mechanism,this paper designs a five-axis hybrid machine structure based on this hybrid mechanism,analyzes its kinematics,static stiffness and working space.The machine has the advantages of high rigidity,strong bearing capacity,no accumulated error of parallel mechanism and the advantages of large working space and the flexibility of the series mechanism.It can achieve the purpose of machining high precision and complex curved surface.The main contents of this paper are as follows:Firstly,according to the processing requirements,compares and analyzes several mechanisms which include(2RPU/UPR+R)+P five degree of freedom hybrid mechanism which proposed by research group qualitatively,finally chooses the hybrid mechanism for the configuration of the five-axis hybrid machine.The axis of(2RPU/UPR+R)+P five degree of freedom hybrid mechanism is analyzed by screw theory,get the conclusion that it has two finite rotational axises.Secondly,closed loop vector method and D-H method are used respectively to analyze the parallel and the series parts of the hybrid mechanism,which obtained several sets of positive solutions.On this foundation,the positive and negative solution model of the whole hybrid mechanism is derived by using the homogeneous transformation matrix,and the calculated results is proved to be correct.Thirdly,on the assumption that only the branches of the mechanism are flexible rods,using screw theory and material mechanics knowledge to derive the stiffness matrix on the basis of the superposition principle under small deformation,and uses the orientation transformation relationship between the branch and the mechanism,which obtaines the static stiffness expression of the whole hybrid mechanism.By carrying on force analysis of the simplified model of the mechanism using finite element software,comparing the deformation value of the end of the mechanism with the theoretical value,the deviation between them is small,which verify the validity of the static stiffness model.Then,under consideration of conditions that moving distance of moving pair,corner restriction and branch bar interference,whole working space of the hybrid mechanism is obtained by using the limit boundary searching method,analyze the characteristics of the space,verify its feasibility which take this mechanism as the configuration to design a hybrid machine tool which can machining large complex structural parts.Finally,complete the choice of machine spindle according to the processing requirements,then the key components and the whole structure of the machine tool are designed,get the static stiffness values of the complete model of the machine tool in the initial pose and other typical positions by using finite element software and compared with theoretical values,which verify the validity of the stiffness model obtained by theoretical deduction above.Then the modal of machine tool is analyzed and its natural frequency and vibration characteristics are obtained.