FUZZY SETS APPROACH TO QUALITY IMPROVEMENT

摘要

On the basis of the theory of fuzzy sets, linguistic quality characteristics may be successfully formalized. Its application to some of the main tools for quality improvement, as listed below, is presented. 1. Pareto analysis with the loss function for transformation of the membership function into loss. 2. Cause-and-effect diagrams with the possible addition of fuzzy relationships between factors and quality characteristics based on expert knowledge. 3. Design of experiments with defuzzification of linguistic data by calculating the distance (d) between the centre of gravity of the fuzzy sets and the target value. 4. d-BAR control charts with the traditional technique for the distance variable d. 5. Capability studies based on set theory both for variable data and for fuzzy linguistic data. The approach presented in this paper makes it possible to use the tools mentioned above in areas where either only a subjective estimation of a quality characteristic is available or the expense and time needed for obtaining quantitative data is uneconomic.