Towards a QFD-based expert system: A novel extension to fuzzy QFD methodology using rough set theory

Quality function deployment (QFD) has been widely recognized as an effective means to develop quality products that can maximize customer satisfactions. This paper presents a novel extension to the fuzzy QFD methodology using rough set theory, with the aim to facilitate decision making in the early stages of product development and lead to the establishment of a QFD-based expert system for product design. The proposed rough-fuzzy QFD system combines fuzzy arithmetic operations with the two novel concepts of rough number and rough boundary interval that are derived from rough set theory. A comparison between the proposed methodology and the traditional fuzzy QFD was performed. It has been shown that the proposed methodology not only can provide more insights into the vague voices of customers and technologists, but also can suppress the enlargement of boundary intervals after each arithmetic operation in QFD analysis. This would help in improving the discernibility of design objectives and thus facilitate the decision making in product development.