On the computation of the information content of a coupled design with two functional requirements

Computing the information content of coupled designs is seldom discussed in the literature, probably because the Axiomatic Design (AD) practitioners know that coupled design solutions should be avoided. On the other hand, Suh's theorem 7 states, "the information contents of coupled and decoupled designs depend on the sequence by which the DPs are changed to satisfy the given set of FRs". From this theorem, one could be tempted to conclude that the information contents of coupled designs cannot be computed, because they have not a "right" sequence for changing the values of the DPs in order to satisfy the given FRs. This misunderstanding could then be used to stress that AD is not useful as a decision-making approach for coupled designs. Yet, coupled designs do exist, they are many times unavoidable and their information contents can be computed, although this is often hard to perform. This paper presents the computation of the information content for the simple case of a 2-FR, 2-DP coupled design and illustrates how this topic is related to Suh's theorem 8 on independence and tolerance. (C) 2015 The Authors. Published by Elsevier B.V.