A logic-based mechanical system constraint model

Abstract

Abstract. Objectives and BackgroundA constraint is a relationship between entities that should be satisfied from certain engineering technology points of view. Design constraints are those imposed on a product (including its components), such as a ground vehicle or a ship, from the perspectives of function (for instance, structural responses of a vehicle component or a ship deck) or activity (for example, manufacturing processes of a vehicle component or maneuvering of a ship) that are encountered in the life cycle of the product. Most design constraints directly or indirectly apply to the geometry and material characteristics of the product.In typical concurrent engineering environments, different aspects of product life cycle are evaluated as simultaneously as possible by different disciplines during the design processes. An engineering discipline is viewed as an expert in one of many aspects of the product life cycle which has very limited knowledge about other engineering aspects. It is possible that the discipline proposes a design change that violates constraints which other disciplines impose. Hence, systematic ways to model and manage product constraints and manage design changes are needed, especially in a concurrent engineering environment. This paper classifies design constraints from a concurrent engineering point of view and presents a logic-based constraint modeling method to effectively describe and manage assembly related geometry constraints for mechanical systems. Since design constraints are recognized and specified by disciplines, the more disciplines are involved, the larger number of types of constraint will be involved. The concurrent engineering environment considered in this paper has a global database, a design data server, a constraint manager, a process manager, and four engineering disciplines: CAD design system, structural analysis, dynamic analysis, and machining process analysis. Each discipline is treated as an application.The global database stores shared definitions of mechanical systems and their performance information for applications [1,2]. The schema of the global database is called a global data model in this paper. All the data sent to or extracted from the global database are managed by the design data server.Each engineering application in the concurrent engineering environment has a local database, whose schema is a local data model. The local database of an application may contain information that is not stored in the global database but is needed for the application [1,2]. For instance, manufacturing resource information (such as capabilities of milling