Tolerance Analysis of Partial Parallel Assemblies Based on Jacobian-Torsor Model

In tolerance analysis of partial parallel assemblies based on the Jacobian-Torsor model, it is difficult to calculate their cumulative tolerance. To solve this problem, a calculation method of fractional steps is proposed in this paper. This method is used to establish functional requirements for these assemblies to produce connection diagrams, describe the process of generating the assembling results, create the Jacobian-Torsor model of parts and components, and calculate variable spinor of the mating surface in the coordinate system of the parts and components. Moreover, a detection algorithm for the spatial relationship of the mating surface is designed, correct physical contact of mating planes is ensured. To attain the optimization goal of the gravity center of assembled parts or components being the lowest, the differential evolution algorithm is used to calculate the cumulative tolerance of partial parallel assemblies design information is fully based to transform from a partial parallel chain to a single series chain in connection diagram. The feasibility of the proposed method is verified through modeling and calculation of steam turbine flow gap. The results show that the proposed method can balance the tolerance and fit information and significantly improve model accuracy and reliability. © 2022, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.