A FUZZY KNOWLEDGE-BASE TO SUPPORT ROUTINE ENGINEERING DESIGN

Much of engineering design can be characterised as putting together va riants of existing mechanisms to meet novel requirements. This paper d escribes an approach to engineering design in which fuzzy sets are use d to represent the range of variants on existing mechanisms. Membershi p functions are chosen to reproduce the distinctions and classificatio ns used by experienced designers. Methods are introduced to calculate the fuzzy performance range achievable by each component type, and a m etric is suggested for the ranking of design candidates against design requirements. The underlying approach to design evaluation derives fr om that developed by Antonsson, Wood and Otto. If the components model the design domain accurately, this architecture will always find a su ccessful design, where one exists. However, finding this design may in volve exhaustive search of the design. space, and the time required fo r such an exhaustive search is typically far greater than is available for the task. The architecture is therefore augmented by the introduc tion of design agents, embodying heuristic rules to direct the search intelligently, so that a satisfactory design is found within a reasona ble length of time. As an example, the method is applied to preliminar y design of a Stirling engine heat exchanger. (C) 1998 Elsevier Scienc e B.V. All rights reserved.