Research On Motion Characteristics And Static Stiffness Of 3 - P & 2 (?) Parallel Mechanism

Topology is an important part of the theoretical system of modern mechanism. Now it’s generally considered the same topology structure has the same kinematic characteristics regardless of the scale parameter (except the singularity). Many studies about topology chart and topology synthesis are based on this theory. But there were few studies about whether the scale parameter can influence the kinematic characteristics (mechanism out of singularity). This thesis chooses 3-P&2（？） parallel mechanism to study the scale parameter’s impact on the kinematic characteristics for the same topology structure and also study the static stiffness.For a 3-P&2（？） parallel mechanism, thirty-five kinds of structures were constructed by changing the scale parameter conditions. The thesis chooses five symmetrical kinds as objects, gives the primary research for kinematic characteristics using the traditional formula for the degree of freedom and kinematic simulations, and finds kinematic characteristics are different for different structures.The forward and invert solutions of the 3-P&2（？） parallel mechanism’s position were obtained based on the 6-P（？） kinematic analysis model. The numerical results of the position’s forward solution were also obtained through Jacobi matrix. This thesis compares the results to the software simulation results. It also finds a general approach to the orientation description using three parameters. It also gives additional explanation of the special structures and provides proof for the translational move of the Delta structure.In the searching of kinematic workspace, this thesis, based on the inverse kinematics, obtains the workspaces of different structures by connecting to the travel restrictions of the input slider and the angle constraints of the spherical hinge. In order to provide a more visual description of the workspace of the structures with rotation, this thesis describes the orientation space using polar coordinates.Based on the superposition principle at small strain and the virtual mechanism method, a quite comprehensive analytical approach of spatial static stiffness is proposed. This thesis gives a finite element analysis of the spatial static stiffness using the finite element analysis software, and compares the results to the numerical results.