Hierarchical Supervisory Control Based on Discrete Event Systems With Flexible Marking

Abstract

This paper proposes a two-level hierarchical supervisory control scheme for a discrete event system (DES), where the low-level is represented in the standard Ramadge-Wonham framework and the high level is represented by a DES with flexible marking (DESFM). As shown, the flexibility in the definition of marking provided by a DESFM simplifies the modeling of the high-level marking behavior. This approach, when compared with other approaches, requires less events and states to model the highlevel, while guaranteeing hierarchical consistency.Index Terms-Discrete event systems (DES), hierarchical control, supervisory control.

Generalised Verification of the Observer Property in Discrete Event Systems

“…6. Also consider that, in some hierarchical control approach one is concerned with the input-output behaviour of the workcell for coordination purposes with other workcells (Cunha and Cury, 2007;Schmidt and Breindl, 2011). Thus, the relevant events are the input event for the workcell x and the two output events a 1 and a 2 , therefore Σ r = {x, a 1 , a 2 , τ}.…”

“…7. One of the most important conditions for hierarchical control approaches like (Cunha and Cury, 2007), , or (Schmidt and Breindl, 2011) is that θ(M ) has to be an OP-abstraction. From definition 1, it can be shown that θ(M ) is not an OP-abstraction by making s = xyzwv 1 rzwv 2 ∈ N and t = a 1 ∈ Σ * r such that θ(s)t = xa 1 ∈ L m (θ(M )), but there is no t ∈ Σ * such that st ∈ L m (M ) and θ(st ) = xa 1 .…”

“…Abstractions obtained by natural projections have been extensively used in the Supervisory Control Theory (Ramadge and Wonham, 1989), as for example in control with partial observation of events (Wonham, 2011), in hierarchical control (Hill and Tilbury, 2006;Cunha and Cury, 2007;Feng and Wonham, 2008;Schmidt and Breindl, 2011), in modular synthesis (Hill and Tilbury, 2006;Schmidt et al, 2006;Feng and Wonham, 2006), in compositional verification of the nonblocking property (Hill and Tilbury, 2006;Flordal and Malik, 2009;Pena et al, 2009;Pena et al, 2010b), among others.…”

“…In (Wong and Wonham, 1996), the abstraction is obtained in the form of a reporter map, which projects strings of events of the original (low-level) model, built from a set Σ, into highlevel strings built from an independent set T of events. Due to some difficulties with the use of reporter maps (Feng and Wonham, 2010), most of the approaches subsequent to (Wong and Wonham, 1996) focus on abstractions ob-tained by the natural projection, which maps strings of the original model into strings of the abstraction, by erasing events of Σ which are not contained in a given subset of relevant events Σ r ⊆ Σ, like in (Wong et al, 2000;Cunha and Cury, 2007;Feng and Wonham, 2008;Schmidt and Breindl, 2008).…”

Metodologia e ferramenta de apoio ao teste de não-conflito no controle modular de sistemas a eventos discretos

“…No controle hierárquico, abstrações são usadas como modelos para o nível gerencial (alto-nível), permitindo a síntese de leis de controle que satisfaçam especificações deste nível da estrutura hierár-quica de controle (Wong e Wonham, 1996), (Torrico e Cury, 2004), (Schmidt et al, 2004), (Leduc et al, 2005), (Cunha e Cury, 2007), (Schmidt et al, 2007), (Hill, Cury, de Queiroz e Tilbury, 2008). Nesse caso, o modelo de alto-nível esconde eventos que correspondem a detalhes operacionais do comportamento do sistema, não-relevantes no mundo gerencial.…”