| At early design stages, the designer must systemically and rationally synthesize both subjective human preference and objective domain physics to create and select purposeful and functional artifacts in order to satisfy the initial design intent. In this process, synthesis plays a critical role in supporting the smooth transition and effective integration of the designer's subjectivity and objectivity. In this dissertation, we propose to formulate and support synthesis as a fundamental reasoning activity/process based on relevant theories that stem from formal logic. On one hand, we define synthesis reasoning as an abductive inference that instantiate the general to the particulars by making both analytic and synthetic propositions under constraints. On the other hand, we prescribe three logic-based reasoning principles that a good synthesis activity/process should follow, namely the instantiation principle, the abduction principle, and the analytic-synthetic distinction principle. Based on these logic foundations, we structure a generic Synthesis Reasoning Framework that guides the designer to go through three sequential stages to carry out a systemic synthesis reasoning in design, namely the formation stage, the ideation stage, and the selection stage. Furthermore, we apply this framework as a general platform upon which to develop some specific supporting approaches in order to address particular synthesis-related design issues in practice including, a constraint management method, an abduction-based ideation procedure, and a preference/axiom alternating selection mechanism. Finally, a rigorous case study is carried out to validate the practical usefulness of the systemic synthesis reasoning at early design stages. On one hand, we investigate the impacts of following each individual reasoning principle during the synthesis process on different metrics of the synthesis result. On the other hand, we compare the different synthesis process and result of using the Synthesis Reasoning Framework with that of using the Axiomatic Design. This research contributes to engineering design both theoretically and practically. In terms of the theoretical contributions: this research enriches and deepens the understandings of synthesis activity/process; it formulates a theoretical foundation and general platform upon which future research of synthesis can be carried on; finally it reveals impacts of the systemic synthesis reasoning on the early-stage design performance. With regards to the practical contributions: this research enhances the practical applications of the Axiomatic Design as a design synthesis theory instead of a design analysis tool in the traditional usage; the proposed framework guides the designer to carry out synthesis reasoning more effectively in design practice; the specific method/procedure/mechanism developed within the proposed framework each resolves a synthesis-related design problem in practice. |
