Supervisor Localization of Timed Discrete-Event Systems under Partial Observation and Communication Delay
For researchers in discrete-event systems, this work provides a method to handle partial observation and communication delays in timed systems, but it is an incremental extension of existing localization techniques.
This paper extends supervisor localization to timed discrete-event systems under partial observation and communication delay, decomposing a monolithic supervisor into local controllers and preemptors that collectively achieve the same controlled behavior. The approach is validated on a timed workcell example.
We study supervisor localization for timed discrete-event systems under partial observation and communication delay in the Brandin-Wonham framework. First, we employ timed relative observability to synthesize a partial-observation monolithic supervisor; the control actions of this supervisor include not only disabling action of prohibitible events (as that of controllable events in the untimed case) but also "clock-preempting" action of forcible events. Accordingly we decompose the supervisor into a set of partial-observation local controllers one for each prohibitible event, as well as a set of partial-observation local preemptors one for each forcible event. We prove that these local controllers and preemptors collectively achieve the same controlled behavior as the partial-observation monolithic supervisor does. Moreover, we propose channel models for inter-agent event communication and impose bounded and unbounded delay as temporal specifications. In this formulation, there exist multiple distinct observable event sets; thus we employ timed relative coobservability to synthesize partial-observation decentralized supervisors, and then localize these supervisors into local controllers and preemptors. The above results are illustrated by a timed workcell example.