Abstract: Satisfying the independence axiom is the basis of axiomatic design (AD) in which coupled design is considered unacceptable. However, product design usually involves coupled design, especially for the design of complex products. To deal with coupled design that appears in design with AD, a structural analytical approach is presented with the intension to achieve product design when functional requirements are independent. First, independent functional requirements and coupled function sets are identified using the partition operation. Then pair wise comparison technique in decision analysis based on triangular fuzzy number is applied to measure the strength of the coupled functions. Next, coupled function planning is carried out to find the processing sequence of the coupled functions by means of the decoupling and the tearing operation. Finally, coupling analysis is conducted to calculate the coupling degree of the coupled design to provide criterion for the evaluation and the selection of the coupled design scheme. The effectiveness of the proposed approach is demonstrated by an illustrative example showing the design of a condenser.

Key words: Axiomatic design, Coupled design, Coupled function planning, Coupled function set, Triangular fuzzy number