Uncertainty Analysis And Parameter Optimization Of Static Characteristics Of Linear Rolling Guide

Rolling guide is a typical movable joint in CNC machine tools,and it is the weak link of CNC machine tools.The static characteristics of the rolling guide have a great influence on the accuracy of the machine tool.The research shows that the joint stiffness can account for 60%-80% of the total stiffness of the machine tool.However,many domestic rolling guide design manufacturers often use experience and analogy methods to design the structural parameters of rolling guide,lacking a set of structural parameter design methods for the static characteristics of rolling guide,in which the uncertainty is the key factor affecting its development.In this paper,the uncertainty analysis of the static characteristics of the rolling guideway is carried out,and the influence law of each uncertainty factor on the static characteristics of the guideway is studied.By solving this model,the structural parameters of the guide rail can be optimized reasonably,the comprehensive static characteristics of the guide rail can be improved and the influence of uncertain factors on the static characteristics of the guide rail can be reduced.The specific work is as follows:(1)Based on Hertz contact theory,a five degree of freedom static stiffness model of rolling guideway under Hertz contact is established.The basic equation method,which is the static stiffness modeling method of rolling guideway under non Hertz contact,is given.Based on this method,a five degree of freedom static stiffness model of rolling guideway under non Hertz contact is established.The friction characteristics of rolling guideway are analyzed,and the effects of preload,tightness and external load on friction are studied The influence law of friction characteristics.(2)The uncertain variables in the rolling guide are given,including straightness error,external load and elastic modulus.The linearity error is described by the combination of small displacement spinor theory and Monte Carlo simulation,and the external load and elastic modulus are described by interval theory.Based on the static stiffness model,the influence of single uncertain variable on the static stiffness of the rolling guide is studied.The uncertain variables to be considered in the optimization of the static stability of the rolling guide are the straightness error of the raceway and the elastic modulus of the guideway.Finally,the influence of preload and straightness on the uncertain static stiffness of rolling guide is studied.(3)Taking the mean value of Y-direction static stiffness,Y-direction static stiffness interval and guide friction as optimization objectives,the standard deviation of Y-direction static stiffness distribution as constraints,and the rolling body diameter and preload as optimization variables,a model of static stability of rolling guide Considering Uncertain straightness error and elastic modulus is established.In order to improve the calculation efficiency,the Latin hypercube sampling method is used to extract 10000 groups of design points in the vector space composed of uncertain variables and optimization variables,and to solve the optimization objectives and constraint function values of each design point.Finally,the response surface model which is easy to obtain the expression is used to construct the response surface model of optimization objective and optimization constraints about uncertain variables and optimization variables.(4)The static characteristic optimization model of the deterministic state rolling guide is established,and the optimization model is solved by the complex method,and the optimal rolling body diameter and preload are obtained.Nested particle swarm optimization algorithm is used to solve the robustness optimization model.The internal cycle defines the influence of uncertain variables on the y-direction static stiffness of the guideway,and the external cycle optimizes the optimization variables.The comparison between the results of robustness optimization and the results of certainty optimization shows that the friction force of the results of robustness optimization is reduced by 17.7% and the stiffness is stable under the premise that the static stiffness of rolling guide is increased by 4.5%.