Procedure-based design is well-established, supporting engineers via expert knowledge codified in resources such as handbooks, tables, and heuristic if-then rules of thumb. These procedures enable even inexperienced designers to benefit from the knowledge obtained by more experienced counterparts through years of practice and discovery. While procedural approaches have many advantages, they do have limitations. They tend to produce only satisficing, rather than optimal, solutions. In addition, they are based on historical designs, so offer little assistance for new system types, and are often descriptive rather than normative in nature. In contrast, normative methods — such as constrained optimization — can resolve many of these issues, but at the cost of significant development effort. Here we present a synergistic hybrid strategy with the objective of capitalizing on established procedure-based design methods for a subset of design problem elements, while incorporating normative strategies for the remaining elements. A design procedure is analyzed to identify steps that involve specification of design variables, and a subset of rule-based steps that could be replaced with optimization algorithms. A single-stage spur gear train design example is used to illustrate this process, and for comparing alternative hybrid solution strategies. Initial results indicate that solution quality can be improved significantly over purely procedure-based design when incorporating limited optimization elements, while maintaining a reasonable level of additional modeling effort.

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