Hierarchical Interface-based Supervisory Control - Part II: Serial Case

In this paper we present a hierarchical method that decomposes a system into two subsystems, and restricts the interaction of the subsystems by means of an interface. We present definitions for two types of interfaces (represented as discrete-event systems (DES)), and define a set of interface consistency properties that can be used to verify if a DES is nonblocking and controllable. Each clause of the definitions can be verified using only one of the two subsystems; thus the complete system model never needs to be constructed, offering potentially significant savings in computational effort. Additionally, the development of clean interfaces facilitates re-use of the component subsystems. Finally, we examine a simple example to illustrate the method.