Including Imprecision in Engineering Design Calculations

The Imprecise Design Tool (IDT) presented in this paper is a working computer implementation of the method of imprecision, a formal theory that represents preferences among design alternatives. An aircraft engine design example indicates how the IDT may be applied to support engineering design decisions, using the Engine Development Cost Estimator provided by General Electric Aircraft Engines, Cincinnati, Ohio. INTRODUCTION Ullman (1992), among others, notes that computers are not widely used in the early phases of engineering design because (1) existing computer tools need a very refined representation of an object on which to operate, and (2) computers are primarily evaluation tools and of limited value in generating concepts. Preliminary design descriptions are characteristically imprecise: the designer has yet to make most of the decisions that will reduce the number of design alternatives considered from many to one. The Imprecise Design Tool (IDT) is a working computer implemen..