Meta-model based multi-objective optimisation method for computer-aided tolerance design of compliant assemblies

摘要

Optimal tolerance design is a time-consuming and multi-disciplinary procedure and involves several aspects of design, manufacturing, quality and cost problems. In addition, the quality of assemblies can be significantly affected by the flexibility of components which has not been considered in most of the previous research. In this paper, a new method is proposed for multi-objective optimal tolerance design of compliant assemblies based on an integrated Kriging meta-modelling - NSGA-II - Shannon's Entropy TOPSIS algorithm. The tolerance propagation of flexible components in the assembly process is modelled through the enhanced Method of Influence Coefficients (MIC). Geometrical variations of key characteristics are estimated through a Kriging model on the data generated from the enhanced MIC based on the finite element method. The overall manufacturing cost is minimised, while the geometric capability ratio (GCR), as a quality criterion, is maximised. To find the Pareto optimal front (POF), NSGA-II is applied. For ranking best alternatives of the POF based on multiple criteria, an improved Shannon's Entropy-based TOPSIS is used. Finally, to verify and demonstrate the efficiency of the proposed method, a case study is considered with the results compared with Monte Carlo simulations and a conventional tolerance allocation method from the literature.