A conceptual approach to the computational synthesis of compliant mechanisms

In contrast to engineering analysis tasks to predict the behavior of an engineered system, the goal of conceptual synthesis is to conceive an appropriate system given only the desired physical phenomena posed in the problem specifications. Conceptual synthesis is the inverse problem of analysis and is challenging due to its open-endedness. In this dissertation, a methodology for the conceptual synthesis of planar compliant mechanisms based on a building block approach is developed. Linear (small displacement and rotation) finite element analysis is used to describe the behavior of the mechanisms. In the building block synthesis, the problem specifications are decomposed into related sub-problems if a single building block cannot perform the desired task. The sub-problems are tested against the library of building blocks until a suitable building block is determined. The final mechanism is composed of an assembly of the building blocks to provide the desired functionality.; In sharp contrast to related research in topology optimization of compliant mechanisms, the building block approach is intuitive and provides key insight into how individual building blocks contribute to the overall function of a mechanism. We investigate the basic kinematic behavior of individual building blocks and relate this to the behavior of a mechanism composed of building blocks. This serves to not only generate viable designs but also to augment the understanding of the designer. Once a feasible concept is thus generated, known methods for size and geometry optimization can be employed to fine tune the mechanism's performance.; The key enabler of the building block synthesis is the method of capturing kinematic behavior using Compliance Ellipsoids. The mathematical model of the compliance ellipsoids facilitates the characterization of the building blocks, transformation of problem specifications, decomposition into sub-problems, and the ability to search for alternate solutions. The compliance ellipsoids also give insight into how individual building blocks contribute to the overall kinematic function of the mechanism.; The effectiveness and generality of the methodology are demonstrated through a number of synthesis examples. Using only a limited set of building blocks, the methodology is capable of addressing generic kinematic problem specifications typical to research in compliant mechanism synthesis. The success of the methodology depends on the quality of the decomposition formulation which directs the creation of solvable sub-problems based on the relationship between the compliance ellipsoids and the problem specifications. Further development of the methodology is presented in the use of instant centers as a tool to aid in the conceptual synthesis of a class of problems.