Preliminary Vehicle Structure Design: An Industrial Application of Imprecision in Engineering Design

Paper number DETC98/DTM-5646

Manuscript accepted for presentation at the
ASME 1998 Design Theory and Methodology Conference
Atlanta, Georgia, Sep. 13-16, 1998

Michael J. Scott
Erik K. Antonsson
Engineering Design Research Laboratory
California Institute of Technology
Pasadena, California 91125


In preliminary vehicle structure design, as in all preliminary engineering design, many important decisions are made informally on the basis of imprecise information. Concerns of styling and manufacturability, for instance, can carry great weight in the design process although they are not modelled by any formal analysis. The Method of Imprecision, or MoI, is a formal method for incorporating imprecise information into a design process, and helps to make preliminary decisions on a sound basis. In a demonstration of the MoI prepared for VW Wolfsburg, concerns of manufacturing, styling, parts availability, and design were incorporated with the engineering analysis of the structural stiffness of a VW Rabbit. The results show the usefulness of the method in trading off these conflicting attributes, including styling preferences and engineering requirements.

Any analysis involving more than two design variables must contend with two difficulties, the exploding need for computation, and the problems of displaying results in several dimensions. The MoI uses optimization and approximations, when feasible, to address the first difficulty, and an interactive graphical tool for preference display was developed and applied here to address the second.

Keywords: Industrial applications of DTM; Vehicle Structure Design; Design Methods and Models; Design Representations; Computational Methods of Design; Fuzzy Sets