Universität Stuttgart
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Item Open Access Agent-based dynamic scheduling for flexible manufacturing systems(2011) Badr, Iman; Göhner, Peter (Prof. Dr.-Ing. Dr. h. c.)The need to react to fluctuations and versatility in market demand and face competition threats has led to the increasing trend to produce a wide variety of product types in small batches. The advent of advanced technology like computerized numerically controlled (CNC) machines and automatic guided vehicles has enabled the realization of flexible manufacturing systems (FMSs). FMSs aim at bringing the efficiency of mass production to small-to-medium sized batch production with high product diversity. This objective calls for scheduling approaches that optimize the utilization of the applied technology and at the same time react to the environmental dynamics flexibly. Conventional scheduling approaches fail to provide a mechanism for reacting to the dynamics of FMSs in a timely and efficient manner. Approaches that cater for optimality by a thorough investigation of available schedule alternatives always fail to exhibit real-time reactivity due to the high complexity of the problem. In this research work, an agent-based concept for the flexible and efficient FMS scheduling is proposed. The inherent complexity of the FMS scheduling problem is tackled by decomposing it into autonomous agents. These agents are organized in a hetrarchical multi-layered architecture that builds on the flexibility of FMSs. Every involved agent applies search heuristics to optimize its assigned task out of its local perspective. Through the interactions among the concerned agents along the different levels of abstraction, the schedule is optimized from the global perspective in reasonable time. Different scheduling modes are supported to account for the different managerial decisions and the different environmental conditions. The generated schedule is adapted to disturbing events such as machine breakdowns based on a schedule repair method that caters for automating the reaction to disturbances efficiently in real-time. In addition, structural changes of FMSs, including the addition of new resources, are incorporated dynamically into the proposed scheduling, which guarantees long-term flexibility.