Stiffness,Dynamics And Sensitivity Analysis Of PaQuad Parallel Mechanism

Funded by the National Science Foundation of China and the Doctoral Fund of the Ministry of Education,this thesis works on the digital and flexible pose-adjusting equipment required by the assemblage of large-scale components in the aviation industry.Taking a pose-adjusting parallel mechanism(referred as PaQuad PM)as example,stiffness modeling and evaluation,elasto-dynamic modeling and parameter sensitivity analysis have been carried out.The following contributions have been made:(1)Through closed-loop vector equations,Inverse position analysis is firstly conducted based on the mechanism features of PaQuad PM.Next,twist and wrench mapping model are established considering the layout of articulated raveling platform and limbs.Then stiffness modeling of PaQuad PM is carried out resorting to deformation superposition principle,Hooke's Law and virtual work principle.Finally,stiffness indices are proposed by instantaneous energy and the stiffness performance of PaQuad PM is evaluated.(2)On the basis of kineto-elastodynamics,elastodynamic models of parts,substructure and PaQuad PM are successively formulated by differential equation of beam element,coupling relationship of nodes and deformation compatibility condition.The inherent characteristic of PaQuad PM is investigated by numerical example then verified by finite element simulation and experiment.(3)Response surface models of stiffness performance,mass and natural frequency are formulated by Latin hypercube design method.Parameter sensitivity indices are defined by the differentiation of reliability function to parameter mean value and variance.Finally,parameter sensitivity analysis of PaQuad PM is implemented and the main parameters are determined.The researches lay a solid foundation to the optimization of PaQuad PM and provide technical support to parallel mechanisms applied in aircraft assemblage of large-scale component.