RELIABILITY ALLOCATION OF HYDRAULIC SYSTEMS FOR COMPUTER NUMERICAL CONTROL (CNC) MACHINE TOOLS BASED ON IMPROVED FUZZY ANALYTIC HIERARCHY PROCESS (FAHP)

Jie Yu, Tiebin Wang, Xinghe Sun, Weidong Wang, and Gege Zhao

Keywords

Computer numerical control (CNC) machine tools, hydraulic system, reliability allocation, fuzzy analytic hierarchy process (FAHP), hierarchical model

Abstract

The complexity of objective things and the vagueness of subjective judgement will bring numerous uncertainties, then result in fuzzy nature of evaluation. The traditional fuzzy hierarchical analysis often leads to inconsistency with the judgement matrix and inaccurate calculation, which needs further check and correction. The improved fuzzy hierarchy method is more effective, more in line with human logic, more simple, more accurate and easier to establish. Therefore, the improved fuzzy hierarchy analysis method is used to evaluate the reliability allocation scheme of the hydraulic system, the core component of computer numerical control (CNC) machine tools’ processing. According to the characteristics of multi-level and multi- factor reliability index along with the coexistence of quantitative and qualitative indexes, the improved fuzzy analytic hierarchy process (FAHP) method is adopted. After comprehensive consideration, six factors affecting the hydraulic system are defined, and the three- scale method is introduced to establish the fuzzy consistency matrix and build the hierarchical structure model. The improved FAHP model is programmed by MATLAB with expert information, and the comprehensive weight of each object layer unit to the target layer is calculated and determined. The reliability allocation of hydraulic system according to the determined weight provides a new idea for the layout and reliability study of such system of CNC machine tools.

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