OPTIMIZATION OF DESIGN UTILITY

Design optimization is often carried out with respect to a single obje ctive, for example, weight, manufacturing cost, quality or robustness. However, when the design process is completed, a design is evaluated with respect to its performance in all of these areas, and possibly ot hers, in addition to mechanical design considerations. We present a de sign method whose basic premise is that the process of design should b e driven from the very beginning by consideration of how the artifact will ultimately be evaluated. A rigorously determined multiple attribu te design evaluation function provides insight necessary to formulate a nonlinear programming problem. A clear distinction is made between d esign attributes and constraints. The objective function is maximizati on of utility. Explicit representations of relationships between desig n decisions and resulting performance in each of several attributes se rve as constraints. An illustrative example of automotive bumper beam design optimization is presented. By coupling the physical relationshi ps between the decision variable beam gauge and the attributes weight, deflection and cost, maximization of the overall worth of terms of th e best combination of these attributes is possible. The solution can b e expressed in terms of elements of a design vector over which the des igner has direct control.