Static Stiffness Modeling And Optimum Design Of Parallel Manipulator Based On (2-UPS+U)PU+2-UPS Mechanism

With the continuous innovation and development of science and technology,parallel manipulators play an increasingly important role in the field of industrial technology.Especially for multi-degree-of-freedom parallel manipulators,because of the small interference between the mechanisms and the compact working space,it is favored by many people.However,during the working process of the mechanical arm,the external force will cause the end effector to deform,which affects its dynamic characteristics and positioning accuracy.Therefore,it is important to study the static stiffness of the parallel manipulator.This paper will mainly study the stiffness of the(2-UPS+U)PU+2-UPS parallel manipulator from the following aspects,and optimize the design based on this.Firstly,the reference coordinates of the dynamic and static platform of the parallel manipulator are established respectively.According to the position and attitude of the end of the manipulator,the input position and attitude parameters of each branch chain are solved.The working space of the parallel manipulator is obtained by the inverse position of the manipulator and the structural parameters of the mechanism,and the flexibility in the working space is analyzed.On the basis of the above,the kinematics and statics mapping model is established,and the corresponding evaluation indicators are defined to analyze which factors have a great influence on the kinematics and static performance of the mechanical arm.Secondly,an analytical model of static stiffness of the parallel manipulator is established.The end deformation is decomposed into the bending deformation of the UPU branch and the tensile deformation of the UPS branch.The stiffness model is established for the two deformations respectively,and then the stiffness of each part is superimposed by the deformation superposition principle,thus establishing the parallel connection.Static stiffness model of the manipulator.For the stiffness model,the stiffness evaluation index is defined to optimize the main design variables that affect the stiffness of the entire arm.In order to achieve multi-objective andmulti-variable optimization purposes,the genetic algorithm is used to optimize the design variables.Finally,the finite element model of the parallel manipulator is established.Because the mechanism is more complicated,the whole mechanical arm is divided into two parts: moving parts and fixed parts.Different parts are used to model each part,and the established parts are saved as macro files.Finally,file calls and coordinates are performed.After the conversion operation,the finite element models of the entire robot arm are obtained by grouping the various components.After loading and analyzing the finite element model of the whole machine,the stiffness results of the analytical model are compared to verify that the analytical model is correct.