A technique to perform design calculations on imprecise representations of parameters has been developed and is presented. The level of imprecision in the description of design elements is typically high in the preliminary phase of engineering design. This imprecision is represented using the fuzzy calculus. Calculations can be performed using this method, to produce (imprecise) performance parameters from imprecise (input) design parameters. The Fuzzy Weighted Average technique is used to perform these calculations. A new metric, called the γ-level measure, is introduced to determine the relative coupling between imprecise inputs and outputs. The background and theory supporting this approach are presented, along with one example. 1.

For decades ships have been designed using the well-known “basis ship approach ” together with the equally well-known Evans-Buxton-Andrews spiral. The two principal limitations of the spiral are that the process of design is assumed to be sequential and the opportunity to include life cycle considerations is limited. It is our contention that in order to increase both the efficiency and effectiveness of the process of ship design a new paradigm for the process of design is needed. In this paper, we review recent developments in the field of design and offer a contemporary paradigm, Decision-Based Design, for the design of ships; one that encompasses systems thinking and embodies the concept of concurrent engineering design for the life cycle.

A technique to perform design calculations on imprecise representations of parameters using the calculus of fuzzy sets has been previously developed [25]. An analogous approach to representing and manipulating uncertainty in choosing among alternatives (design imprecision) using probability calculus is presented and compared with the fuzzy calculus technique. Examples using both approaches are presented, where the examples represent a progression from simple operations to more complex design equations. Results of the fuzzy sets and probability methods for the examples are shown graphically. We find that the fuzzy calculus is well suited to representing and manipulating the imprecision aspect of uncertainty in design, and probability is best used to represent stochastic uncertainty. 1

Research efforts for automating the design process of mechanical artifacts have been intensified in recent years. A variety of approaches have been proposed. However, as is usual in a new field, no unified theory or terminology has yet emerged. This situation is complicated further by lack of general agreement on what constitutes "design". Evidently, some common framework or vocabulary is necessary for researchers to be able to communicate and compare their efforts. This paper attempts to outline such a vocabulary and examines, by example, how it could be used to review current published research in mechanical design automation.