Fuzzy approaches to evaluation in engineering design

As variables in the design evaluation stage are imprecise (fuzzy), tools, such as fuzzy set theory, should be used. This paper presents several fuzzy approaches to design evaluation. Weights of criteria and performance levels are captured by fuzzy numbers, and the overall performance of an alternative is calculated through the new fuzzy weighted average. Different approaches to express and calculate performance are discussed. Two metrics for measuring performance levels per criterion of a solution are proposed. Also, a new type of fuzzy goal is suggested. Finally, a novel way of comparing the overall performance of a design candidate by drawing an aggregate profile of performance is proposed. It is concluded that fuzzy set theory is a powerful and flexible tool for dealing with the imprecision in different types of problems in design evaluation.