Distributed Supervisory Control of Discrete-Event Systems with Communication Delay

TL;DR

This paper introduces a method to verify delay-robustness in distributed supervisory control of discrete-event systems, allowing for communication delays and identifying which events are delay-critical.

Contribution

It presents a new computational test for delay-robustness in distributed controllers, relaxing the assumption of negligible communication delays.

Findings

Delay-robustness can be verified using the proposed test.

Some events are delay-critical, others are not, in the context of communication delays.

The approach is demonstrated on a workcell model with three agents.

Abstract

This paper identifies a property of delay-robustness in distributed supervisory control of discrete-event systems (DES) with communication delays. In previous work a distributed supervisory control problem has been investigated on the assumption that inter-agent communications take place with negligible delay. From an applications viewpoint it is desirable to relax this constraint and identify communicating distributed controllers which are delay-robust, namely logically equivalent to their delay-free counterparts. For this we introduce inter-agent channels modeled as 2-state automata, compute the overall system behavior, and present an effective computational test for delay-robustness. From the test it typically results that the given delay-free distributed control is delay-robust with respect to certain communicated events, but not for all, thus distinguishing events which are not delay-critical from those that are. The approach is illustrated by a workcell model with three communicating agents.