Basic Theory Analysis Of A 4-PRP+3-UPS&PU Redundant Drive Hybrid Machine Tool Mechanism

Today,with the development of manufacturing and heavy industry,CNC machine tools undoubtedly play an important role.As a new type of NC machine tool,parallel machine tool has been paid much attention by domestic and international scholars and industrial manufacture since its birth.Because of its strong carrying capacity,rigidity of machine tools,high machining accuracy and fast response,it has broad application prospects.It is called "twenty-first Century machine tools".Hybrid machine tools are proposed on the basis of parallel machine tools.The hybrid machine tool can inherit all advantages of the parallel machine tool,and make up the disadvantage of the small working space of the parallel machine tool.Because redundant driving can overcome singularity,optimize the stability of machine tool drive and improve the driving force of joint,it has also become a new trend of NC machine tool design.In this paper,a new six degree of freedom redundant drive hybrid machine tool is designed for machining heavy complex and precision integral structural parts in heavy industry,and a series of basic theoretical analysis is carried out for this machine tool.The main research contents are as follows:The configuration and mechanism analysis of the hybrid machine tool mechanism4-PRP+3-UPS&PU are described in detail.Including: the coordinate system of machine tool is established;Based on screw theory,the constraint reaction force in the mechanism is analyzed,and the motion form and output freedom degree of the mechanism are determined,the correctness of the calculation of degrees of freedom is verified by the G-K formula that was corrected by Huang.Singularity analysis and drive input selection of machine tool mechanism is carried out based on the screw theory.The kinematics performance of the hybrid machine tool is analyzed,and the complete kinematics model is established.The inverse position equation of the mechanism is established by the analytic vector method and the geometric relation.The influence coefficient matrix of the first order motion-the Jacobian matrix,and the two order influence coefficient matrix-Hessian matrix are established by the influence coefficient method.The dynamic modeling of the hybrid machine tool is carried out by Lagrange method.The kinetic energy and potential energy are analyzed,and the equivalent generalized force of the non-conservative force acting on the machine tool is calculated.The Lagrange equation is listed,and the mapping matrix between driving force and external force is obtained.The static and static stiffness analysis of the hybrid machine tool are carried out.The static equilibrium equations is listed,and the static transfer matrix between the platform and the drive rod and the constraint branches is solved.Based on the screw theory and the small deformation superposition principle,the overall flexibility matrix and stiffness matrix of the mechanism are obtained,and the static stiffness model of the hybrid machine tool is established.Three dimensional modeling of the hybrid machine tool is carried out by using PRO/E software,and a virtual prototype is constructed.Combined with numerical examples,the kinematics model,dynamic model and static stiffness model of the machine tool are calculated by using MATLAB mathematical analysis software.The ADAMS software is used to verify the calculation results,and the correctness of the basic theoretical analysis and the feasibility of the machine tool mechanism are proved.Laying the foundation for the realization of machine tools.