The Analysis Of Structure And Kinematics Of Parallel Metamorphic Mechanism Based On Screw

Parallel metamorphic mechanism combines the advantages of parallel mechanism and metamorphic mechanism.Parallel metamorphic mechanism has high precision and high stability,but also can switch degrees of freedom and motion configuration.One parallel metamorphic mechanism can realize the functions of multiple separate versions of parallel mechanisms,which has strong flexibility and applicability.Therefore,the research on the parallel metamorphic mechanism has important practical significance and application prospects.First of all,in order to solve the incomplete expression of mechanism information and the inability to express compound hinges in the existing description methods of metamorphic mechanism configuration changes,a motion screw encoding incidence matrix description method is proposed.This method merges the motion screw coding with the incidence matrix in graph theory.The article presents the operation rules of the motion screw encoding incidence matrix in the process of metamorphic mechanism configuration change,and verifies the correctness and feasibility of the motion screw encoding incidence matrix through the configuration transformation of two examples of the compound hinge mechanism and the 3RPS parallel metamorphic mechanism.Secondly,a new type of(MT)P(MT)metamorphic branch is designed by studying metamorphic branch.The metamorphic branch can be switched to three different configurations by locking,which are equivalent to TPT branch,RPT branch and RPR branch respectively.A new type of 4(MT)P(MT)parallel metamorphic mechanism is composed of metamorphic branch chains,a dynamic platform and a static platform.The parallel metamorphic mechanism has 4 different degrees of freedom and 15 different configurations.In this paper,the screw theory is used to analyze and verify the characteristics of the degrees of freedom of some configurations from 1-DO to 4-DOF.At the same time,the calculation results are verified according to the modified Kutzbach-Grubler degree of freedom calculation formula,and the 3D simulation of these 15 different structures is done through PROE.Thirdly,the four-degree-of-freedom 4TPT configuration and the three-degree-of-freedom 3TPT-1RPT configuration are analyzed for the positive and negative positions.The numerical results of the positive and negative solutions are compared to verify the correctness of the solution.At the same time,on the basis of the algebraic expression of the inverse position solution,the velocity and acceleration characteristics of the two configurations are analyzed and deduced by using the direct derivation method.Finally,this paper uses MATLAB to draw the working space of the parallel metamorphic mechanism in 4TPT configuration and 3TPT-1RPT configuration,and analyze the singularity and dexterity in these two configurations.According to the above research,the description method of metamorphic mechanism configuration is enriched.At the same time,the above research provides reference for the mechanism synthesis and kinematic analysis of the parallel metamorphic mechanism,and provides ideas for the subsequent research on the parallel metamorphic mechanism.