Miguel Cavique

An Axiomatic Design Interpretation on the Use of Response Surface Methodology to Solve Coupled Designs

The most important design decisions are made in the outset of the designing process, when the knowledge about the final design solution is usually scarce and therefore uncertainty is high. According to the independence axiom of Axiomatic Design (AD), design solutions are classified in the following three basic types: uncoupled, decoupled and coupled, the former being the best type and the latter the poorest. As a rule, coupled designs should be avoided, not only because they infringe the independence axiom but also because their information content is hard to compute. Nonetheless, we argue that the occurrence of coupled solutions is noteworthy in general design, although we recognize that they are questionable and that many times they could be easily avoided. Our motivation is to contribute for changing the current state of affairs by showing how to use the minimum information content axiom to make early decisions in the development of coupled designs. One of the general engineering approaches to deal with multiple-FR, multiple-DP designs is the Response Surface Methodology (RSM). We will show in our paper how RSM can be used to deal with coupled designs as if they were uncoupled. The conclusion is that one can graphically compute the information content of coupled designs with two DPs and an arbitrary number of FRs by using multiple RSM. This means that RSM can be interpreted at the light of Axiomatic Design, and embodies an appropriate approach to support decision-making in the case of coupled designs.Copyright

Some Peculiarities of the Redundant Design Solutions

In common speech, the term redundant is used to label superfluous repetitions that as a rule should be avoided. Nevertheless, redundancy is a linguistic tool that can play a remarkable role in the communication of complex thoughts in both the vernacular and the erudite talking or writing, which includes the field of engineering design. In the Axiomatic Design (AD) point of view, redundancy may increase the complexity of the design solutions (which is measured through their information content), but does not necessarily entail the breach of the ADs independence axiom. Hence, redundant solutions should not be excluded in a regular basis, since the ones that comply with the independence axiom are considered good design. According to this line of reasoning, the pertinence of redundant solutions should be assessed in the onset of the designing processes, bearing in mind the virtues of the likely higher simplicity of the non-redundant solutions. This paper deals with some basic concepts related to redundant design and it should be seen as a contribution to bring more insight on a subject that is not thoroughly reviewed in the known literature. Different forms of redundancy are considered, specifically the reliability motivated active and passive types, and the functionality-related alternative and augmentative kinds. The means to perceive intrinsic redundancy through the examination of the design equations are also provided, as well as some illustrative examples. The implicit conclusions are that redundant designs are much more usual that one can think at a first glance, and that the study of their peculiarities might deserve further attention.