Dynamic setup scheduling and flow control in manufacturing systems

In this paper we propose a method for flow control of parts in a manufacturing system with machines that require setups. The setup scheduling problem is investigated in the context of a multilevel hierarchy of discrete events with distinct frequencies. The higher level of the hierarchy calculates a target trajectory in the surplus/backlog space of the part types which must be tracked at the level of setups. We consider a feedback setup scheduling policy which uses corridors in the surplus/backlog space of the part types to determine the timing of the setup changes in order to guide the trajectory in the desired direction. An interesting case in which the target trajectory leads to a target point (e.g. a hedging point) is investigated in detail. It is shown that in this case the surplus/backlog trajectory at the setup level can lead to a limit cycle. Conditions for linear corridors which result in a stable limit cycle are determined.