engleski

MODELING AND SIMULATION OF MANUFACTURING SYSTEMS

In this paper we present a methodology for modeling and simulation of dynamical discrete event systems (DDES), predominantly flexible manufacturing systems (FMS). Proposed technique is based on the matrix representation of a manufacturing system. Although prerequisites that are required for an event to start are given by static model of DES, we are not able to tell in which particular moment these prerequisites are met, i.e. we do not know when the event actually starts. In real applications on actual manufacturing processes, we will be sensing the completion of prerequisite jobs by either using sensors (e.g., proximity, tactile, etc.) or via notification from the machines or resources. On the other hand, for the purpose of computer simulation, we must find a way to keep track of time lapsed in the processing of jobs. To keep track of jobs time durations, we incorporated the system dynamics into the matrix model in a form of an extended lifetime. That is, a real number di, called a lifetime, is associated with each task in an MS. Problem that we analyze in the paper is that when described as a bill-of-material (BOM), or in some other engineering form, the job sequence does not disclose potential difficulties that might develop when the structure of an MS, which executes this particular sequence, is determined. In the paper we show how two of these potential difficulties, conflict and deadlock, can be exposed by using static and dynamic simulations of an MS. Based on the matrix model, these simulations provide a complete insight in the system performance.

Manufacturing Systems; Matrix-algebra; Modeling; Simulation

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