Distributed Supervisory Control of Discrete-Event Systems with Communication Delay

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

Modeling and synthesis of event-transferring communicating decentralized supervisors for discrete-event systems

This work models and synthesizes communicating decentralized supervisors for Discrete-Event System (DES) which communicate the information about observed events. This is done within the authors' framework of Distributed Supervised DESs (DSDESs), using agent-wise labeling maps to reveal the informational dependencies among the supervisors. Communication between every two supervisors is modeled by the maps from the sender's observable events to its set of recently observed event, or an empty set. Thereby, the synthesis of communicating decentralized supervisors is reduced to the design of these maps

Decentralized Supervisory Control of Discrete-Event Systems over Communication Networks

In this paper we investigate the problem of designing embedded decentralized discrete-event con-trollers over communication networks. It is assumed that there is a path between every pair of processes in the network. The control objective is specified by a prefix-closed language which is controllable and observable, but not coobservabe. The paper is focused on communication among processes necessary to meet the control objective. As such, process models are left unspecified; it is only required that disabling any of the controllable events does not block communication among processes. Our findings support the idea that in the presence of ideal communication channels the protocol design for non-coobservable specifications can be reduced to the synthesis of communicating decentralized supervisors, and we propose solutions for a restricted class of problems. Also a couple of positive results are stated for the case where channels are unreliable. Index Terms decentralized supervisory control, discrete-event systems, protocol design. I

SILICEOUS SPONGES AND MICROBIALITE CARBONATE MOUNDS AND THEIR ENVIRONMENT AT THE SINEMURIAN OF NZALA AND FOUM TILLICHT, CENTRAL HIGH ATLAS (MOROCCO)

The Nzala and Foum Tillicht outcrops that occur North of Rich village, are part of the Sinemurian carbonate mounds well exposed all over the Midelt-Errachidia transect in central High-Atlas (Morocco). These mounds constitute the upper part in the upper member of the Idikel formation, dated by ammonites, in the Lower-Upper Sinemurian transition. They locally grow in the Upper Sinemurian and disappear at the bottom of the Lower Carixian. The biosedimentological study of these carbonate mound, allowed the distinction between three different sets: a lower set (25 m) where the carbonate mounds are simple shaped and small sized boundstones, dominated by calcified sponges in a life position, including hexactinellides sponges, lithistids demosponges and non-rigid Demospongiae; a medium set (35 m) which shows complex shaped and big sized constructions including sponges and different thrombolytic fabric (clotted, digitate and dendrolitic). And an upper set, the most developed (150 m) consists of a vertical arrangement of lenticular structures of metric width and decametric extension where the thrombolites and sponges are very rare. This set shows some solitary corals and a hardened surface rich in ammonite of the base of lower carixian. The analysis of an elementary mound type show, essentially two parts: - A massif micritic-dominated core, which is a boundstone dominated by siliceous sponges and microbialites with associated encrusting forms (Radiomura, Serpula and Terebella, Tubiphytes and Bryozoans), beside, brachiopods, pelecypods, gastropods, isolated corals, ostracods, hyaline foraminifera and ammonites. - A well bedded sediments, corresponding to the core lateral synchronous, showing a biocalcarenitic facies a proximal to the core and a biomicritic facies further laterally. Brachiopods and echinoderms are particularly abundant. Complete or fragmented bivalve and gastropod shells are common. The studied outcrops resulted volumetrically dominated by siliceous sponges and microbialites that represent the major constructor and stabilizer, in addition to such benthic assemblage described previously, suggest an open marine depositional environment, infratidal to circatidal and relatively low energy