Decision Fusion and Supervisor Synthesis in Decentralized Discrete-Event Systems

We study a problem in decentralized supervisory control coined the Global Problem (GP) by Rudie and Wonham (1992). The objective is to nd local supervisors that generate languages that lie in a speci ed range of closed languages. We present results for a version of this problem called the Special Global Problem, (SGP) where the lower end of the range is empty and the higher end of the range is a closed and regular `legal' language. To this end, on-line local supervisors are synthesized that generate a language that contains the supremal closed controllable and strongly decomposable (supCCSD) sublanguage of the legal language. We accomplish this task through a new, more general decentralized supervisory control architecture involving decision fusion. We formulate two problems that extend GP and SGP. These are GP with Fusion (GPF) and SGP with Fusion (SGPF). Our main result is a set of local supervisors that solve SGPF for any k-out-of-n type event fusion rule. This result is of particular interest when more than one supervisor has control over the same event. Furthermore, the local supervisor designs are decoupled, thus the (on-line) computation of local supervisors can be performed in a distributed manner.