Optimization of design utility

Design optimization is often carried out with respect to a single objective, for example, weight or manufacturing cost. Weight, cost, quality and robustness are each important considerations in design evaluation. 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. The process of design should be driven from the very beginning by consideration of how the design artifact will ultimately be evaluated. We present a method for design analysis whose basic premise is that design analysis should be based on a rigorously determined multiple attribute design evaluation function. The evaluation function provides insight necessary to formulate a non-linear programming problem. A clear distinction is made between design attributes and design constraints. The objective function is maximization of utility. Explicit representations of relationships between decisions which designers make and resulting design 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 design decision variable beam gauge and the attributes weight, deflection and cost, maximization of the worth of the design in 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.