An Integrated System for Design of Mechanisms by an Expert System—DOMES: Theory

Abstract

Methodologies have been developed and implemented in LISP and OPS-5 languages which address type synthesis of mechanisms. Graph theory and separation of structure from function concepts have been integrated into an expert system called DOMES (D esign O f M echanism by an E xpert S ystem) to effectively implement the following three activities: (1) enumeration of all nonisomorphic labelled graphs; (2) identification of those graphs which satisfy structural constraints; (3) sketching of a mechanism corresponding to a given graph. Developed theories and algorithms are applied to a Robot Gripper design [19] and a Variable Stroke Piston Engine design [16]. The results from these two applications indicate that the automated techniques effectively identify all previously obtained solutions via manual techniques. Additional solutions are also identified and several errors of the manual process are detected. The developed methodologies and software appear to perform a complete and unbiased search of all possible candidate designs and are not prone to the errors of the manual process. Other important features of DOMES are: (1) it can learn and reason, by analogy, about a new design problem based on its experience of the problems previously solved by the system; (2) it has the capability to incrementally expand its knowledge base of rejection criteria by converting into LISP code information obtained through a query-based interactive session with a human designer; (3) it can select the set of rejection criteria relevant to a design problem from its knowledge base of rejection criteria. These procedures could become a powerful tool for design engineers, especially at the conceptual stage of design.