A decentralized object-oriented computer integrated manufacturing control system
Carroll, Dennis James
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This dissertation presents and analyzes an object-oriented design of a fully decentralized computer-integrated manufacturing system. The intelligence of the system is dispersed among the cells of the system allowing greater ability to adapt to changes in system configuration. A necessary component of the design is a scheduling strategy for the movement of physical and logical objects through the system. This research proposes and compares two potential scheduling strategies for such a system. The system consists of a set of nodes which serve as temporary hosts for mobile "objects." Each mobile object is responsible for finding its own way through the system based on a process program contained in the object. Each mobile object contains its own copy of a process program and a full description of the path for the object through the system is contained in the process program. A resident attendant object, which serves mobile objects, commands the node to perform a required set of actions based on the mobile object's process program. The attendant object then locates and transfers the mobile object to an available node at the next level to perform the next set of functions of the process program. The potential robustness of this type of system stems from the redistribution of coordinating intelligence from a central controller to the mobile objects. Addition or removal of nodes is completely dynamic as all scheduling and negotiations take place only as needed and without the services of a central controller. Therefore, no single failure can completely and immediately halt such a system except for failures of unique nodes and global network media failures.