Optimization of Design Utility

Design optimization is often carried out with respect to a single objective, 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 others, in addition to mechanical design considerations. We present a design method whose basic premise is that the process of design should be driven from the very beginning by consideration of how the artifact will ultimately be evaluated. A rigorously determined multiple attribute design evaluation function provides insight necessary to formulate a nonlinear programming problem. A clear distinction is made between design attributes and constraints. The objective function is maximization of utility. Explicit representations of relationships between design decisions and resulting performance in each of several attributes serve as constraints. An illustrative example of automotive bumper beam design optimization is presented. By coupling the physical relationships between the decision variable beam gauge and the attributes weight, deflection and cost, maximization of the overall worth of terms of the best combination of these attributes is possible. The solution can be expressed in terms of elements of a design vector over which the designer has direct control.