Research on the Comprehensive Allocation Method for a Vehicle Hydraulic Braking System Based on Partial Fuzzy Ratings and Considering Failure Correlation

Abstract

Vehicle hydraulic braking systems are widely used, structurally complex. Reliability allocation during the design phase is crucial, yet there is a relatively limited body of research on this subject. In response, a new method for vehicle hydraulic braking system is proposed: the comprehensive reliability allocation method based on partial fuzzy ratings and considering failure correlation (CRA-PFRAFC). Based on the analysis of reliability allocation criteria impacting the braking system, the fuzzy set theory is introduced into the comprehensive allocation method, and the criteria with strong subjective dependence are fuzzy evaluated. The braking system allocation model is established by Gumbel Copula function. According to the set reliability target, the model is solved to allocate the failure rates to each subsystem according to the allocation vector. An example illustrates the advantages of this method. The results show that the reliability of the brake assembly is the lowest, while the reliability of the vacuum booster system is the highest. By fuzzy rating the failure severity and failure occurrence, the subjective quantification problem in traditional method is avoided. Meanwhile, compared with the traditional subsystem independent assumption model, this method is more realistic, and the failure rate of subsystem allocation is increased by 20% on average. Therefore, this study provides necessary and effective theoretical basis for reducing the design and manufacturing costs of vehicle hydraulic braking systems.