A Feature-Oriented Tolerance Specification Design Method

This dissertation studies the "A Feature-oriented Tolerance Specification Method" with the support of the National Natural Science Foundation of China(51575484).The key technologies of tolerance specification are studied based on the Geometrical Product Specification and Verification framework and previous study,which include the operator of DRF selection,operator of geometric tolerance selection,the optimation of geometric tolerance selection operator etc.The main research works are summarized as follow:1)With the requirements of new generation Geometrical Product Specification and Verification framework,a diagram and some fundamental rules of the feature-oriented tolerance specification method are modelled based on geometrical character,position relation and contact relation.2)A strategy for DRF selection is proposed based on statistical learning method.A normalized vector is formulated to express the characteristic of a feature,i.e.geometric,contact and positioning characteristics of a feature.The statistical learning method is used for building some classifiers to discriminate datum feature vectors.The diagram of the DRF selection is also studied.The effectiveness of the method is verified via an example.3)An axiomatic design based method is proposed for geometrical tolerances selection.The variation of a feature is decomposed based on kinematics by an operation.The independent and information axiom is used to build rules and operator for geometric tolerances selection of a feature.The effectiveness of the geometric tolerance selection method is verified via an example.4)A MADM based method is proposed for optimizing the operator of tolerances selection.To optimize the operator,several attributes are modeled.An entropy-based method is applied to select the optimization decomposition scheme for the operator,and then the optimized tolerance can be calculated by the optimized operator.The effectiveness of the optimization is verified via an example.5)A prototype tolerance specification system is developed by C#and Solidworks API,which is intergrated in Solidworks.To verify the effectiveness of the feature-oriented tolerance specification method and the prototype system,a comprehensive case study of RV reducer is presented.