Kinematic Design And Stiffness Modeling Of Pose-Adjustment Parallel Mechanisms With An Articulated Travelling Platform

In order to meet requirements of the aircraft assemblage for the pose-adjustment equipment in the large-scale component docking, a novel one-translational-three-rotational(1T3R) parallel mechanism with an articulated travelling platform is proposed. The thesis carries out the topology synthesis, kinematic analysis and optimal design, stiffness modeling and analysis of this type of 4 degree-of-freedom(DoF) parallel mechanisms. The following contributions have been made.Topology Synthesis. Based upon Lie Group/Lie Algebra, the topology synthesis process of 1T3 R 4-DoF parallel mechanisms with an articulated travelling platform is proposed. According to the type of articulated travelling platform and the layout of open-loop limbs, the topology synthesis of this novel type of parallel mechanisms with an articulated travelling platform is discussed in detail, and then numerous novel topology structures are invented.Kinematic Analysis. Without loss of generality, one of the synthesized topology structures is selected as a typical example which is named as PaQuad. Utilizing the closed-loop vector method, the inverse position analysis of PaQuad is carried out, and then the reachable workspace of PaQuad is obtained by means of the boundary search algorithm. Based upon screw theory, the motion/force mapping model of PaQuad is formulated.Dimensional Synthesis. By taking the reciprocal product of a wrench on a twist with specific physical meaning as the virtual power coefficient, the local and global kinematic performance indices are formulated. Considering all constrained conditions and formulating the objective function on the basis of the global kinematic performance indices, the dimensional synthesis of PaQuad can be considered as a nonlinear programming problem with appropriate constraint conditions.Stiffness Modeling and Analysis. Based upon the force and deformation mapping model, a semi-analytical stiffness model of PaQuad is formulated. Comparing with the stiffness results in typical configurations obtained by FEA software and the semi-analytical stiffness model, the validity of the semi-analytical stiffness model of PaQuad is proved.The aforementioned work laid a solid foundation for the prototype design and manufacture of PaQuad parallel mechanism.