Parasitic Evolution And Dynamic Performance Of Host-parasite Robot Mechanisms

In order to improve the mechanism performance of tandem industrial robots as well as to quickly and accurately model and analyze the elastic dynamics of the improved complex robots,based on the study of spatial linkage mechanisms with local degrees of freedom,this doctoral dissertation proposes an optimal design method of host-parasitic bionic mechanisms and reveals the parasitic evolution mechanism between parasitic branched chain and degrees of freedom distributions.Taking the host-parasitic robot as the research object,a fitting elastic dynamic modeling method based on few computational units and multi-experimental fitting was proposed by using the experimentally measured stiffness,natural frequency and vibration displacement curves,and this method can significantly improve the computational efficiency and computational accuracy of the model.On this basis,the parasitic evolution law of the robot stiffness distribution and the dynamic response characteristics of the robot were analyzed,and the effect of variable stiffness on the residual vibration of the robot was further investigated.The research content of this article includes the following aspects:(1)Inspired by the host-parasite relationship of trees and vines in nature,a spatial polycyclic mechanism optimization design method based on the host-parasite relationship in biology was proposed by using the design thinking of structural biomimicry.The hierarchical relationship in the degrees of freedom across various sub-mechanisms of a mechanism with local degrees of freedom features was characterized as a host-parasite relationship similar to the biological community,and a symbol expression method and basic parasitism mode of host-parasite mechanisms were proposed.According to the parasitic evolution relationship between parasitic branched chain and degree of freedom,a new host-parasite robot was designed.All drivers of the robot were designed into counterweights through parasitic branched chain.The centroid stability of the robot was improved and the driving torque of the joint was effectively reduced through gravity balance.(2)Based on the evolution law of host-parasite mechanism,through the stiffness experiment of four limit postures in the robot working space,a method was established to fit the experimental static stiffness analysis with the stiffness matrix analysis.Based on the whole robot,the significant relationship between tensile deformation,bending deformation,torsional deformation and the characteristic parameters of stiffness matrix structure was revealed,and the fitting conditions of the characteristic parameters of the mechanism that meet the calculation of multi-posture stiffness distribution were studied.On the basis of experimental fitting,a stiffness distribution modeling method consisting of very few computational elements was proposed based on finite element method and Lagrange equation.By applying this modeling method,the stiffness values of all postures in the whole working range were calculated,and the efficiency and accuracy of stiffness calculation were significantly improved.Through the comparative analysis of the stiffness distribution of six evolution configurations of host-parasite robots,the parasitic evolution law between the parasitic branched chain and the stiffness distribution of robots was revealed.(3)A fitting elastic dynamics modeling method based on very few computational units and multi-experimental fitting was proposed.Firstly,the elastic dynamic model of hostparasite robot was established based on finite element method and Lagrange equation,and the corresponding comprehensive fitting factors were introduced for the characteristic boundary conditions constituting the stiffness matrix,mass matrix and Rayleigh damping matrix of the mechanism.Using the experimentally determined stiffness,natural frequency and vibration displacement curve conditions,the stiffness matrix,mass matrix and damping matrix of the robot were fitted by multi-experimental fitting from the global point of view,so as to improve the calculation efficiency and calculation accuracy of the model.On this basis,the dynamic performance of the novel host-parasite robot was analyzed from three aspects:dynamic characteristics,time-domain dynamic response,and frequency-domain dynamic response.(4)The residual vibration amplitude at the end of the robot was changed by the variable stiffness ability of the parasitic branched chain.The residual vibration reflects the dynamic performance of the robot in the process of stopping at the predetermined position when the external load stops after the robot end reaches the predetermined position.In order to improve the position accuracy of the wrist stop process at the end of the robot and reduce the maximum amplitude of the residual vibration at the end,the variable stiffness law of the stiffness change at the end of the robot due to the change of the position and posture of the parasitic branched chain was analyzed first at the farthest working posture,and then the variable stiffness process of the parasitic branched chain of the robot was synchronously coupled with the residual vibration process at the end of the robot;the coupled residual vibration process was modeled and solved by the KED method,and then the effect of the variable stiffness characteristics of the parasitic branched chain on the residual vibration at the end of the robot was analyzed.