| During service process,the kinematic accuracy of precision machinery is affected by manufacturing errors,wear,and other factors,and the kinematic accuracy has uncertain evolution characteristics over time.Realizing kinematic accuracy analysis is of great significance for solving the manufacturing problems of precision machinery such as precision radar antennas and lithography machines in China.Kinematic accuracy is the most intuitive reflection of the quality performance of mechanical structures with relative kinematic function,and kinematic accuracy analysis aims to predict the service performance of products.For the above precision mechanical assembly,if traditional tolerance analysis methods are still used to predict and analyze its assembly accuracy to ensure kinematic accuracy,it is inevitable that there will be a certain gap between the actual performance and predicted performance of product due to service conditions.The reason for above problem is due to the unclear correlation between assembly accuracy and kinematic accuracy,and the unclear formation mechanism of kinematic deviation.To solve above problems,this dissertation comprehensively considers the geometric deviation factors affecting the kinematic accuracy of product in the stages of tolerance design,manufacturing,assembly and service,and realizes the evaluation of tolerance design according to the functional requirement of kinematic accuracy by constructing the prediction relationship model between tolerance and kinematic accuracy in the design stage,so as to make the tolerance analysis closer to the service state of the product and guarantee the performance requirements of the product.The following five aspects of work are carried out in this dissertation:1.Aiming at the problem that the generation of form deviations in the existing researches of modelling skin model shapes is not combined with the real surface morphology characteristics of the parts,according to the requirements of the geometric specification of the products,the high fidelity modelling method of the skin model shapes is proposed based on the Non-Gaussian random field combining the process of generating form deviations of the parts,and the accuracy of the proposed Non-Gaussian skin model shapes(NSMS)is verified through the physical test,so that it can provide a reliable tolerance representation model for the assembly accuracy analysis of mechanical products in the design stage.2.Aiming at the problem that the existing research on assembly accuracy analysis of plane-type parts does not consider the influence of the spatial distribution characteristics of form deviations on the assembly accuracy,especially when the local surface deformations of mating surfaces are considered,which may further affect the assembly accuracy analysis.Based on the boundary element method,the analysis method of local surface deformations of non-ideal non-rigid planar mating surfaces is proposed considering form deviations,then the analysis method of the relative positioning deviation of the planar mating surfaces is proposed considering the spatial distribution characteristics of form deviations and local surface deformations based on NSMS.On the basis of the above researches and Jacobian-torsor model,the Jacobian-NSMS model is proposed to realize the propagation analysis of the assembly deviation for planar parts considering spatial distribution characteristics of form deviations and local surface deformations,and to reveal the influence law of the spatial distribution characteristics of form deviations and local surface deformations on the assembly accuracy of planar parts.3.Aiming at the problem that the existing assembly accuracy analysis of cylindrical parts does not consider the influence of spatial distribution characteristics of form deviations on assembly accuracy,especially when considering local surface deformations of mating surfaces,different fit mode,and the uncertainty of contact position and contact area,which leads to difficulties in the assembly accuracy analysis,firstly,the judgment method for the fit mode of shaft-hole assembly is presented considering form deviations based on the NSMS of cylindrical parts so as to provide a theoretical basis for further analyzing the assembly deviation analysis of shaft-hole assembly with different fit modes under the given tolerance requirements;secondly,based on the data registration method,the analysis method of relative positioning deviation of cylindrical mating surfaces for tight fit is investigated considering form deviations and local surface deformations,to reveal the influence law of form deviations and local surface deformations on the assembly deviation for tight fit under given tolerance requirements;finally,based on the constraint registration method and boundary element method,the relative positioning deviation analysis method of the cylindrical mating surfaces for loose fit is proposed,and then the influence law of the spatial distribution characteristics of the form deviations and local surface deformations on the assembly accuracy of the cylindrical parts for loose fit is revealed.4.Aiming at the problem of assembly accuracy loss of parallel machinery caused by without considering the variability of the assembly process and local surface deformations of the mating surfaces in the existing researches,firstly,based on the proposed Jacobian-NSMS model,the assembly deviation analysis method of serial machinery is firstly presented considering form deviations and local surface deformations combing with the variability of the assembly process of the parts;secondly,in view of the problem that the existing methods do not consider the influence of local surface deformations when analyzing the relative positioning deviation of parallel connections,based on the algebraic operation algorithm,an analysis method for the relative positioning deviation of parallel connection is proposed considering the influence of form deviations,local surface deformations,and geometric structure in combination with the assembly process of the parts;finally,based on the Jacobian-NSMS model,the assembly deviation analysis method of parallel machinery is proposed considering form deviations and local surface deformations,and the influence law of form deviations and local surface deformations on the assembly accuracy of parallel machinery is revealed,so as to realize the accurate tolerance analysis of parallel machinery.5.On the basis of above researches,aiming at the difficulty of tolerance analysis of precision machinery involving revolute clearance joints due to the space and time-variant uncertainty(STVU)of the form deviations of revolute clearance joints caused by wear during service,firstly,based on the 3-D space-time random field,a modelling method of the 3-D space-time refinement model of the wear-caused form deviations is investigated;then,based on the NSMS of cylindrical parts,the modelling method of dynamic skin model shapes(DSMS)of cylindrical surface is proposed,which can describe the space and time-variant uncertainty of the form deviations,and the dynamic evolution law of the tolerance model is revealed;secondly,based on the DSMS,the research on the characterization and analysis method of rotation error of revolute clearance joint considering STVU of form deviations is carried out,and an integrated Jacobian-NSMSDSMS model is further developed for tolerance analysis based on Jacobian-Torsor model,where the influence of tolerance on kinematic accuracy can be analyzed;finally,the validity of the proposed method is verified by case studies,which reveals the influence law of tolerance on kinematic accuracy. |
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