Hierarchical modelling of manufacturing systems using discrete event systems and the conflict preorder

This paper introduces Hierarchical Interface-Based Supervisory Control using the Conflict Preorder and applies it to the design of two manufacturing systems models of practical scale. Hierarchical Interface-Based Supervisory Control decomposes a large system into subsystems linked to each other by interfaces, facilitating the design of complex systems and the re-use of components. By ensuring that each subsystem satisfies its interface consistency conditions locally, it can be ensured that the complete system is controllable and nonblocking. The interface consistency conditions proposed in this paper are based on the conflict preorder, providing increased flexibility over previous approaches. The framework requires only a small number of interface consistency conditions, and allows for the design of multi-level hierarchies that are provably controllable and nonblocking.