Much of engineering design can be characterised as putting together variants of existing mechanisms to meet novel requirements. This paper describes an approach to engineering design in which fuzzy sets are used to represent the range of variants on existing mechanisms. Membership functions are chosen to reproduce the distinctions and classifications used by experienced designers. Methods are introduced to calculate the fuzzy performance range achievable by each component type, and a metric is suggested for the ranking of design candidates against design requirements. The underlying approach to design evaluation derives from that developed by Antonsson, Wood and Otto.
If the components model the design domain accurately, this architecture will always find a successful design, where one exists. However, finding this design may involve exhaustive search of the design space, and the time required for such an exhaustive search is typically far greater than is available for the task. The architecture is therefore augmented by the introduction of design agents, embodying heuristic rules to direct the search intelligently, so that a satisfactory design is found within a reasonable length of time.
As an example, the method is applied to preliminary design of a Stirling engine heat exchanger.