Figure 5 - uploaded by Robert Valette
Content may be subject to copyright.
Petri net of the second example This section discusses the issue of deadlock in batch systems. A toy example is considered to introduce the main issues. For more complex examples of deadlock in batch systems see 11]. Let us consider the owsheet in gure 4. The process system is made up of two reactors (Re 1 and Re 2). We assume that the master recipe suggests two options: either a rst operation (Op 11) is done in Re 1 and then a second operation (Op 13) is done in Re 2 or Op 21 is done rst in Re 2 and then Op 23 is done in Re 1. This functioning is depicted by the Petri net in gure 5. The three sequential processes (the p-invariants) are:

Petri net of the second example This section discusses the issue of deadlock in batch systems. A toy example is considered to introduce the main issues. For more complex examples of deadlock in batch systems see 11]. Let us consider the owsheet in gure 4. The process system is made up of two reactors (Re 1 and Re 2). We assume that the master recipe suggests two options: either a rst operation (Op 11) is done in Re 1 and then a second operation (Op 13) is done in Re 2 or Op 21 is done rst in Re 2 and then Op 23 is done in Re 1. This functioning is depicted by the Petri net in gure 5. The three sequential processes (the p-invariants) are:

Source publication
Article
Full-text available
The purpose of this paper 1 is to illustrate the benefits of a Petri net based approach for control and monitoring of event-driven operations in process systems. A Petri net based specification contains structural information which is absent from a simple state transition graph. The verification scheme is not necessarily based on a state enumeratio...

Similar publications

Chapter
Full-text available
Active rules are a mechanism to provide a reactive behavior to software systems. They are not exempt to have errors, which can be introduced inadventently during their development phase. Determining if a rule set is free of errors, involves to verify its correcteness. In this work, we first extend the error definitions given for production rules,...

Citations

... In this section, we propose the on-board detection and diagnosis module included in AUTODIAG. [11,31,36,42,46,83], alarm correlation [40,56] or the diagnoser [22,45,59,75]. In these works, the model of the system to diagnose is a behavioral model including both normal operations and faults. ...
Article
Full-text available
Generally, diagnosis methods use one kind of knowledge only (i.e., a model, a numerical data base, a base of previously solved cases, and so on). Even if these methods perform well on simple enough systems, they are restrictively efficient for complex systems like cars. In practice, it is impossible or too expensive to acquire all the knowledge necessary to their implementation (complete modeling of the system, cases representing all the possible breakdowns, etc). The approach followed in this paper is to use different and heterogeneous kinds of knowledge into an integrated diagnosis tool. This is done by using different diagnosis methods in particular Model-based Reasoning, Pattern Recognition and semantic information retrieval. The MODE framework then enables all these methods to collaborate defining the required inputs and the possible outputs of each method and proposing a general scheduler sequencing the applications of each method depending on the available data and the user decisions. This framework is illustrated on a scenario issued from the automotive domain.
... Fault detection and diagnosis of discrete event systems have been the subject of many studies. Thus, it has been proposed some Petri nets approaches to fault diagnosis (Boubour et al., 1997;Hadjicostis and Verghese, n.d.;Valette, 1995;Jiroveanu and Boel, 2005;Genc and Lafortune, n.d.;Lefebvre and Delherm, 2005), alarm correlation approaches (Jakobson and Weissman, 1993;Nygate, n.d.) and diagnoser approaches (Contant et al., 2002;Lamperti and Zanella, 2003;Pencolé, 2004;Sampath et al., 1998). In these works the model of the system to diagnose is a behavioral model including both normal operation and faults. ...
Conference Paper
This paper deals with an approach for the detection and localization of intermittent faults in discrete events systems with partial observability. The proposed methods are based on a discrete events model representing the normal functioning of the observable behavior of the monitored system. This model based on the Petri net formalism is built from the design data. The detection mechanism consists of a comparison between the flow of observable events emitted by the monitored system and the flow foreseen by the model. A localization step complete the detection mechanism and points out the set of events potentially responsible for the faults. These two mechanisms are designed in order to operate on-board, in real time. An example from the automotive domain is presented.
... This can lead to a deadlock resulting from a siphon which is empty. A classical example of deadlock in the case of batch systems is presented in [16]. An approach for deadlock avoidance is shown in [4,15]. ...
... The detection function is then followed by a diagnosis function in order to identify the reasons of such an inconsistency between the state of the system and the state of the model. The problem of the detection based on a model of the process is presented in details in [16]. Each time a token becomes available, we verify if it enables a transition. ...
Article
The approach presented in this article is based on the real time simulation of p-time Petri net for the real time scheduling of batch systems. After defining the different kinds of constraints that can exist in a linear hybrid production system, we present the conflict resolution principle used by a token player algorithm at the global coordination level.
... The later seem particularly suitable for modelling of recipe based operation because a Petri net model, compared to a simple state transition diagram, contains additional structural information. This information enables certain properties of the model to be examined without the problem of state explosion (Valette, 1995). ...
Article
Abstract Faculty of Electrical Engineering, University of Ljubljana, Slovenia Flexible batch plants are characterised,by combination,of discrete and continuous,dynamics.,Several processes,taking place inside batch reactors are best described,by continuous,dynamics. The sequence,of steps required to make,a prod- uct, on the other hand, can be very well described by discrete event dynamics system representation. Such sequences are defined by batch recipes. A design methodology,for such recipe driven process operation,based on recipe models is proposed. Supervisory,control framework,is employed,to combine,procedures,defined by recipes with co-ordination and resource-allocation,functions. A simulation support for the proposed,design approach,is discussed,and an example of a corresponding,simulation,tool is presented. An application example,of a batch process,cell controller design is presented,to illustrate the described,concepts. 0 1998 Elsevier Science Ltd. All rights reserved. Keywords: modelling, simulation, discrete event systems, Petri nets, process control, batch processing
Article
Full-text available
This paper deals with the dynamic semantics of a new proposed for-malism, called Object Oriented High Level Petri Nets (OOHLPN). In the first part of the paper, the formal definition of OOHLPN is briefly introduced, and an example of using OOHLPN is provided. The second part of the paper pre-sents the dynamic semantics of OOHLPN. First, the semantics of Extended High Level Petri Nets with Objects (EHLPNO) is described. These nets are based on standard of High Level Petri Nets, enriched with some object-oriented concepts. Next, the semantics of OOHLPN is described using notions of state, marking, step and step firing. The third part of the paper presents some algo-rithms for implementing the dynamic semantics of OOHLPN.
Article
Full-text available
Institut de G enie des Proc ed es (INPT-ENSIGC) 18, chemin de la loge 31 078 Toulouse C edex R esum e L'automatisation des proc ed es batch est rendue diicile par leur sp eciicit e de fonctionnement qui fait coop erer les aspects continus et discrets. D es qu'on lui conf ere un caract ere g en eral, le processus ne peut ^ etre approch e par une mod elisation int egralement con-tinue ou int egralement discr ete. Il faut donc faire appel a la fois aux techniques d'automatisation s equentielle (s e-quence d' ev enements traduisant des etats discrets suc-cessifs) et continue (ma^ de trajectoires de variables d' etats continues). Cette automatisation nous conduit a une architecture de commande hi erarchis ee dont le super-viseur est de nature hybride. Le syst eme de commande propos e est pr esent e a travers l'exemple d'un r eacteur batch exothermique dont le contr^ ole de temp erature est eeectu e par un syst eme thermique multiiuide.
Article
Full-text available
This paper deals with interactive storytelling for games. The principle used in narration is based on Campbell's heroes journey. The paper begins by introducing Campbell analysis and then presents how this model has been transformed in a pattern for interactive storytelling. Then, it shows how this model can be used for educational games. Finally an experimentation is presented showing an implementation of this interactive storytelling in the field of a game using a robot.
Article
Batch processes are fundamentally different from continuous chemical processes in both their design and operations, which pose a diversity of problems to system engineering and process control. As an emerging methodology for batch processes, Petri net has found its applications in different aspects of modelling, qualitative and quantitative analysis, supervisory and co-ordinate control, planning and scheduling, and hybrid system design. In this paper, recent research on Petri net applications in batch processes is presented, and future directions are discussed.
Article
Advanced manufacturing processes are normally characterised by large numbers of controlled machinery and processes (e.g., lathes, milling machines, conveyors, robots, etc.), whose synchronisation and precision is paramount to the quality of the ultimate product. Coordination and control of such environments is normally a long term planning project. To accommodate effective planning and automation of many manufacturing processes, real-time discrete-event simulation methods have been developed to simulate and test the conditions likely to be encountered in manufacturing. Continuous simulation packages have also been used (independently of discrete simulators) to increase product reliability and production flexibility. Since for most processes the utilisation and control of resources and equipment is a continuous-time event, a purely discrete-time simulation would only produce approximate results. On the other hand, an entirely continuous simulation system would be insufficient to provide process optimisation only possible through logistic control. The work described here aims to bridge this gap through a simulation package which combines both discrete-event and continuous-time simulation.
Conference Paper
We present an approach of arc-timed Petri nets to online monitoring and predictive simulation for resource allocation in disturbance situations in recipe-driven batch processes. Our approach assumes underlying sequential controllers which control the process and provide signals indicating the state transitions of the real process. We monitor the sequence of process steps and their duration. Predictive simulation is performed to help the operator to find a reasonable resource allocation strategy in case of a deviation. The system has been implemented within a process control system and will be tested on a laboratory batch process