Controller design and conflict resolution for discrete event manufacturing systems

A modern system theory point of view is offered for the design of sequencing controllers for discrete event manufacturing systems with shared resources, whereby the controller is considered as separate from the workcell. The controller design algorithm is based on the required task sequence and the available resources; it is described by linear (i.e. matrix) and nonlinear logical equations using the negative logic. The controller-workcell interaction expressed both in qualitative and quantitative terms allows a rigorous analysis of shared-resource conflicts. The rule-based controller contains inner loops where no shared-resource conflict resolution is required, and extra control inputs to resolve conflict where needed. An example gives an overview of the applicability of the theoretical results. Compatibility with other analysis/design techniques such as Petri-net-based top-down and bottom-up approaches, logical control, (R,max,+) state equations is also addressed. Three methods of conflict resolution are given and related to current work