We report on using problem partitioning and constraint-guided search as a generalized approach to problem-solving in preliminary design. Specifically, a generic design template has been created as a tool to structure information to facilitate problem-solving in three different domains. The approach has been tested through the implementation of knowledge-based systems for the preliminary design of mechanical springs, composite sublaminates and expert systems. Information in each implementation has been partitioned as hierarchical levels of abstraction related through constraints. Function identifies the top level design goals to reduce the search involved for feasible solutions. Goal-directed search, driven by the design application and top-down refinement, reduces the number of possible alternatives. The commonalities extant in the domains have been represented as design goals at three levels of abstraction in the design template. Similar frame-based knowledge representations with inheritance hierarchies and mixed reasoning have been developed for the KEE™-based implementations in each domain. Distinctions among the domains have been modelled as low level slots in the frame hierarchy.
Parametric studies in the domains of mechanical springs, composite sublaminates and expert systems indicate that the minimum number of decision levels required to characterize the preliminary design process in these domains is three; fewer levels would be insufficient to fundamentally characterize the designs. Further, it is observed hierarchical structuring of design information facilitates capturing the interactions among design variables at different levels of abstraction. By using the template representation and reasoning in other divisible domains, the effectiveness of our approach can be further investigated.