A Unified Tolerance Analysis Method Based On Homogeneous Transformation Maodified Matrix For Rigid-compliant Hybrid Model

The dimensional variation and the shape deviation of the part are unavoidable in the manufacturing process.These deviations accumulate and superposition in the assembly process which have an significantly influence on product appearance and performance.Assembly accuracy is one of the cores of product quality assurance.Tolerance analysis is an important means to shorten the product development cycle,improve product quality and reduce the cost of development.The proper tolerance design directly affects assembly deviation and manufacturing cost.Therefore,it is essential to carry out tolerance analysis and assembly quality verification in the design stage.The existing tolerance analysis methods are only for rigid or flexible parts which are not completely applicable for rigid-compliant hybrid model.How to establish an unified and effective tolerance analysis method and predict the distribution of KPC(Key Product Characteristic)accurately for rigid-compliant hybrid model is an urgent problem for tolerance technology.Focusing on the limitations of existing computer-aided tolerance technology,an unified tolerance analysis method based on homogeneous transformation modified matrix and method of sensitivity analysis are proposed in this thesis.The main contents are listed as the following aspects:(1)The development history and research status of computer-aided tolerance technology are summarized.The research background and significance of this paper are introduced.(2)The tolerance technology based on the new generation GPS is introduced.The tolerance is indicated as the characteristic change.By analyzing the relation among the product,part,and feature,tolerance modeling is realized with SDT theory.The assembly relationship of the product is refined to the constraint relation among the features.(3)An unified tolerance analysis method for rigid-compliant hybrid model is proposed.Information of position,orientation of parts and tolerance zone are expressed in the form of matrix.The KPC is represented with the help of homogeneous transformation.The assembly deformation is simulated through FEA(Finite Element Analysis)and the simulation result is used to modify the original variation buildup.The accurate prediction of the KPC for rigid-compliant hybrid model is achieved?(4)A method of sensitivity analysis based on Monte Carlo method is proposed.Based on the differential theory,the tolerance field is divided into several small quantities to calculate the change of the KPC caused by the tiny amount of tolerance zone.The value of the sensitivity is equal to the quotient of the two variables.Multiple sensitivities are calculated and the mean value represents the final sensitivity value.The whole process is programmed in MATLAB.(5)A case study of car chassis employing proposed methodology is presented and demonstrated by 3DCS software.