Discovering Petri Net Models of Discrete-Event Processes by Computing T-Invariants

International audienceThis paper addresses the problem of discovering a Petri Net (PN) from a long event sequence representing the behavior of discrete-event processes. A method for building a 1-bounded PN able to execute the events sequence S is presented; it is based on determining causality and concurrence relations between events and computing the t-invariants. This novel method determines the structure and the initial marking of an ordinary PN, which reproduces the behavior in S. The algorithms derived from the method are efficient and have been implemented and tested on numerous examples of diverse complexity. Note to Practitioners—Model discovery is useful to perform reverse engineering of ill-known systems. The algorithms proposed in this paper build 1-bounded PN models, which are enough powerful to describe many discrete-event processes from industry. The efficiency of the method allows processing very large sequences. Thus, an automated modeling tool can be developed for dealing with data issued from real systems

Partial Reconfiguration of Control Systems using Petri Nets Structural Redundancy

This paper deals with the partial reconfiguration of the discrete control systems due to resource failures using the structural redundancy of the global system model. The approach herein proposed introduces a new subclass of Interpreted Petri Nets (), named Interpreted Machines with Resources (), allowing representing both the behaviour of a system and the resource allocation. Based on this model, an efficient reconfiguration algorithm is proposed; it is based on finding the set of all redundant sequences using alternative resources. The advantages of this structural reconfiguration method are: (1) it provides minimal reconfiguration to the system control assuring the properties of the original control system, (2) since the model includes resource allocation, it can be applied to a variety of systems such as Business Processes, and FPGAs, among others, (3) it takes advantage of the implied features of Petri net models, such as structural analysis and graphical visualization of the system and control. The method is illustrated through a case study that deals with a manufacturing system controller, which includes both alternative resources and operation sequencesITESO, A.C.CINVESTA

Wireless Sensor Networks Formation: Approaches and Techniques

Nowadays, wireless sensor networks (WSNs) emerge as an active research area in which challenging topics involve energy consumption, routing algorithms, selection of sensors location according to a given premise, robustness, efficiency, and so forth. Despite the open problems in WSNs, there are already a high number of applications available. In all cases for the design of any application, one of the main objectives is to keep the WSN alive and functional as long as possible. A key factor in this is the way the network is formed. This survey presents most recent formation techniques and mechanisms for the WSNs. In this paper, the reviewed works are classified into distributed and centralized techniques. The analysis is focused on whether a single or multiple sinks are employed, nodes are static or mobile, the formation is event detection based or not, and network backbone is formed or not. We focus on recent works and present a discussion of their advantages and drawbacks. Finally, the paper overviews a series of open issues which drive further research in the area

A Comparative Analysis of Recent Identification Approaches for Discrete-Event Systems

Analogous to the identification of continuous dynamical systems, identification of discrete-event systems (DESs) consists of determining the mathematical model that describes the behaviour of a given ill-known or eventually unknown system from the observation of the evolution of its inputs and outputs. First, the paper overviews identification approaches of DES found in the literature, and then it provides a comparative analysis of three recent and innovative contributions

Automated modelling of reactive discrete event systems from external behavioural data

International audienceThis paper deals with automated modelling of reactive discrete event systems (DES). A software tool for building automatically interpreted Petri net models from an observed system's input/output sequence is presented. The tool is based on a black-box identification method that processes the input/output sequence, and synthesises and draws the model corresponding to such a sequence. First, the identification method is outlined; then the developed software is described and applied to an illustrative example from the manufacturing area

Adaptative models of flexible manufacturing systems

This papes deals with the rapid reconfiguration or task controllers of flexible manufacturing systems (FMS). This problem is concerned whit the ability of the task coordination system to adapt dynamically to new situations issued from changes on the production requirements or from failures.CINVESTA

Association Between Preexisting Versus Newly Identified Atrial Fibrillation and Outcomes of Patients With Acute Pulmonary Embolism

Background Atrial fibrillation (AF) may exist before or occur early in the course of pulmonary embolism (PE). We determined the PE outcomes based on the presence and timing of AF. Methods and Results Using the data from a multicenter PE registry, we identified 3 groups: (1) those with preexisting AF, (2) patients with new AF within 2 days from acute PE (incident AF), and (3) patients without AF. We assessed the 90-day and 1-year risk of mortality and stroke in patients with AF, compared with those without AF (reference group). Among 16 497 patients with PE, 792 had preexisting AF. These patients had increased odds of 90-day all-cause (odds ratio [OR], 2.81; 95% CI, 2.33-3.38) and PE-related mortality (OR, 2.38; 95% CI, 1.37-4.14) and increased 1-year hazard for ischemic stroke (hazard ratio, 5.48; 95% CI, 3.10-9.69) compared with those without AF. After multivariable adjustment, preexisting AF was associated with significantly increased odds of all-cause mortality (OR, 1.91; 95% CI, 1.57-2.32) but not PE-related mortality (OR, 1.50; 95% CI, 0.85-2.66). Among 16 497 patients with PE, 445 developed new incident AF within 2 days of acute PE. Incident AF was associated with increased odds of 90-day all-cause (OR, 2.28; 95% CI, 1.75-2.97) and PE-related (OR, 3.64; 95% CI, 2.01-6.59) mortality but not stroke. Findings were similar in multivariable analyses. Conclusions In patients with acute symptomatic PE, both preexisting AF and incident AF predict adverse clinical outcomes. The type of adverse outcomes may differ depending on the timing of AF onset.info:eu-repo/semantics/publishedVersio

Stepwise Identification of Automated Discrete Manufacturing Systems

International audienceThis paper deals with the identification of discrete event systems that are automated through a programmable logic controller (PLC). The behavior of the closed loop system (PLC and Plant) is observed during its operation and is represented by a single long sequence of input/output vectors. The proposed method allows building stepwise an interpreted Petri net model, which is updated when new behavior is observed. The identification strategy is composed of several polynomial time algorithms implemented in a software tool that creates and draws the IPN model