MODELING IMPRECISION AND UNCERTAINTY IN PRELIMINARY ENGINEERING DESIGN

Each stage of the engineering design process, and particularly the preliminary phase, includes both imprecision and uncertainty. This paper presents a method by which the imprecision and uncertainty in the description of the design's components can be represented. Fuzzy set theory provides the foundation of the approach. Extended hybrid numbers are introduced to handle the two separate representations of imprecision and uncertainty. These representations include the designer's judgements. An application of the theory to machine design is presented, emphasizing the imprecision usually found in the preliminary design of machine elements. Results show the performance of each design alternative compared to its functional requirements, as well as the coupling between the design parameters and the resulting performance parameters. © 1990.