Global Model For The Management Of Operating Modes In Discrete Event Systems H. Kadri * S. Zairi * B. Zouari * * LIP2 Laboratory, University of Tunis El Manar, 2092 Manar II, Tunisia; (e-mail: Hela.Kadri@isi.rnu.tn, Sajeh.Zairi@fst.rnu.tn, Belhassen.Zouari@fst.rnu.tn ). Abstract: Formal modelling techniques can be exploited for the operating modes management in discrete event systems (DES). In this context, this paper presents a coloured Petri nets (CP- nets) based approach modelling and managing system behaviour on the basis of a multi-model design. Each model (CP-net) represents an operating mode of the system which is activated when exceptional events occur, such as failure, loss of a resource or failed resource recovery. Based on supervisory control theory, the proposed approach designs automatically a global CP- net model via a developed algorithm. Generated model takes into consideration the aspects of mode activation/deactivation, starting state and handling of resource states common to multiple operating modes. Add to the simulation possibility, formal verification of the global CP-net properties is also enabled based on the proposed CP-net model. Such feasibility represents one of the major differences distinguishing the proposed method of all the existing simulators dedicated to operating mode management. Keywords: Discrete event systems; Petri nets; Operating modes; Supervisory control; Reconfiguration; Formal verification; simulation. 1. INTRODUCTION On the initiative of Man, automated systems are char- acterized by high complexity and flexibility. The need for reliability and robustness applications associated with this type of system continues to increase. This condition is more important for discrete event systems (DES) which can lead to unexpected failures with serious consequences. Methods offering advantageous solutions to safe control and failure reactivity include those based distinctively on operating modes management. This technology involves matching each mode to specific system behaviour (engage- ment or disengagement of different system components) and specific tasks and controlling the switching between the modes. In this paper, we adopt a multi-model approach, in which only one operating mode is activated at a time, whilst other modes must be deactivated. This allows us to define separate behaviour of the system for each model under specific control based on supervisory control theory (SCT) (initiated by Ramadge and Wonham [1989]). However, in this theory, the size of the resulting model increases expo- nentially with the number of components and controller synthesis becomes a laborious process. Based on Coloured Petri net (CP-net)(Jensen [1997]), our objective is to propose a formal model with reasonable size and analysis of the whole system such as deadlock/livelock freeness and reachability properties. The proposed framework is developed from several CP-net models and specifications of switching events and it aims to achieve the following goals: • representing all components composing the consid- ered system while avoiding the problem of state space explosion. • associating a model to every operated mode, which allows to define a separate behaviour for each mode and to apply a different control strategy to each one. • defining a clear switching mechanism from one model to another when exceptional events occur while pre- serving common components states. The paper is organized as follows: Section 2, provides a survey of existing approaches dedicated to the operating mode management and particular works based on Petri nets. Section 3, presents the proposed CP-net model rep- resenting the adopted multi-model approach and related hypothesis. Section 4, presents an experimentation of the method. Section 5, concludes. 2. RELATED WORKS Operating mode management for DES remains a chal- lenging problem and is the subject of considerable re- search(Adepa [1981], Asarin et al [2000], Chafik and Niel [2000], Hamani et al [2004], Nourelfath et al [2004], Ka- mach et al [2005], Zouari et al [2007],Faraut et al [2009]). Existing work on operating mode management for DES focuses on problems of characterisation and switching be- tween modes (Adepa [1981], Asarin et al [2000]). However, these approaches are not based on any formal models: 6th IFAC Conference on Management and Control of Production and Logistics The International Federation of Automatic Control September 11-13, 2013. Fortaleza, Brazil 978-3-902823-50-2/2013 © IFAC 420 10.3182/20130911-3-BR-3021.00028