Hierarchical Interface - based Supervisory Control

In this thesis we present a hierarchical method that decomposes a system into a high level subsystem which communicates with n ≥ 1 parallel low level subsystems through separate interfaces, which restrict the interaction of the subsystems. We first define the setting for the serial case (n = 1), and then generalise it for n ≥ 1. We present a definition for an interface, and define a set of interface consistency properties that can be used to verify if a discrete-event system (DES) is nonblocking and controllable. Each clause of the definition can be verified using a single subsystem; thus the complete system model never needs to be constructed, offering significant savings in computational effort. Additionally, the development of clean interfaces facilitates re-use of the component subsystems. We next provide a set of algorithms for evaluating these properties, and show that the algorithm’s time complexity for evaluating a system is O(m2), where m = n+1 is the total number of subsystems. Finally, we present the application of the method to a model of the Atelier Interétablissement de Productique (AIP), a large (7 × 1021 possible states), highly automated, manufacturing system.