Appraisal of conceptual designs: Coalescing fuzzy analytic hierarchy process (F-AHP) and fuzzy grey relational analysis (F-GRA)

The importance of concept selection in the engineering design process cannot be overemphasized. It is a major activity that can assist manufacturers to identify optimal conceptual design before prototyping can commence. This article presents the identification of optimal conceptual design by hybridizing two Multi-Criteria DecisionMaking (MCDM) models which are; Fuzzy Analytic Hierarchy Process (F-AHP) and Fuzzy Grey Relational Analysis (F-GRA). The selection of F-AHP and F-GRA is based on the ability of the F-AHP to determine weights of design features and sub-features without prejudice and the ability of the F-GRA to create comparability elements for the design concepts considering their distances from an ideal design. An extensive analysis on the formulation of mathematical model for the two MCDM models is presented which is followed by the application of the hybridized model to the appraisal of conceptual designs of pipe bending machine. The hybridized model provided satisfactory results by its ability to identify one of the designs as an optimal design considering the values obtained from the fuzzified grey relational grades. The performance of the model was validated by a sensitivity analysis using two defuzzification methods and various values of the distinguishing or resolving coefficient. The variation of the resolving coefficient shows that the application of the hybridized model to design concept selection is viable in terms of stability and uniformity over a wide range of resolving coefficient.