A metamodel of operational control for discrete event logistics systems
Sprock, Timothy A.
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Discrete Event Logistics Systems (DELS) are a class of dynamic systems that are defined by the transformation of discrete flows through a network of interconnected subsystems. The DELS domain includes systems such as supply chains, manufacturing systems, transportation networks, warehouses, and health care delivery systems. Advancements in computer integrated manufacturing and intelligent devices have spurred a revolution in manufacturing. These smart manufacturing systems utilize technical interoperability and plant-wide integration at the device-level to drive production agility and efficiency. Extending these successes to enterprise-wide integration and decision-making will require the definitions of control and device to be extended and supported at the operations management and the business planning levels as well. In the future, smart operational control mechanisms must not only integrate real-time data from system operations, but also formulate and solve a wide variety of optimization analyses quickly and efficiently and then translate the results into executable commands. However in contemporary DELS practice, these optimization analyses, and analyses in general, are often purpose-built to answer specific questions, with an implicit system model and many possible analysis implementations depending on the question, the instance data, and the solver. Also because of the semantic gap between operations research analysis models such as job-shop scheduling algorithms and IT-based models such as MES, there is little integration between control analysis methods and control execution tools. Automated and cost-effective access to multiple analyses from a single conceptual model of the target system would broaden the usage and implementation of analysis-based decision support and system optimization. The fundamental contribution of this dissertation is concerned with interoperability and bridging the gap between operations research analysis models and practical applications of the results. This dissertation closes this gap by constructing a standard domain-specific language, standard problem definitions, and a standard analysis methodology to answer the control questions and execute the prescribed control actions. The domain specific language meets a broader requirement for facilitating interoperability for DELS, including system integration, plug-and-play analysis methods and tools, and system design methodologies. The domain-specific language formalizes a recurring product, process, resource, and facility description of the DELS domain. It provides a common language to discuss our systems, including the questions that we want to ask about our systems, the problems that we need to solve in order to answer those questions, and the mechanisms to deploy the solution. A canonical set of control questions defines the comprehensive functional specification of all the decision-making mechanisms that a controller needs to be able to provide; i.e. a model of analysis models or a metamodel of operational control. These questions refine the interoperability mechanism between system and analysis models by mapping classes of control analysis models to implementation and execution mechanisms in the system model. A standard representation of each class of control problems is only a partial solution to fully addressing operational control. The final contribution of this dissertation constructs a round-trip analysis methodology that completes the bridge between operations research analysis models and deployable control mechanisms. This contribution formalizes an analysis pathway, from formulating an analysis model to executing a control action, that is grounded in a more fundamental insight into how analysis methods are executed to support operational control decision-making.