Emmanuel Castelain

A method for hierarchical modeling of the command of flexible manufacturing systems

The present paper focuses on the modeling of the command and proposes a hierarchical and modular approach which is oriented on the physical structure of FMS. The requirements issuing from monitoring of FMS are discussed and integrated in the proposed model. Its modularity makes the approach open for extensions concerning as well the production resources as the products. As modeling tool, we have chosen object Petri nets. The first part of the paper describes desirable features of an FMS command such as safety, robustness, and adaptability. As it is shown, these features result from the flexibility of the installation. The modeling method presented in the second part of the paper begins with a structural analysis of FMS and defines a natural command hierarchy, where the coordination of the production process, the synchronization of production resources on products, and the internal coordination are treated separately. The method is rigorous and leads to a structured and modular Petri net model which can be used for FMS simulation or translated into the final command code. >

Petri net modeling of ratio-driven flexible manufacturing systems and implications on the WIP for cyclic schedules

In this paper we present a systematic approach of modelling ratio-driven flexible manufacturing systems with Petri nets. We focus on the impact of universal or dedicated transport resources and the way the operation sequences are modeled as closed loops. For a particular problem setting, minimizing the necessary work in process (WIP) while saturating the critical machines, we show that the modeling approach based on timed event graphs, in the way it is commonly used, may induce unnecessary constraints on the WIP. In order to overcome this problem we propose a new technique for the modeling of production ratios and establish tight lower bounds for the WIP, giving thereby a measure for the performance increase obtained.

Hierarchical and dynamic production control in flexible manufacturing systems

Abstract Job shop control involves directing the flow of products through the manufacturing system. Centralized and decentralized approaches have been proposed. This paper introduces first a mix approach in the organization of real time control level in flexible manufacturing systems: a hierarchical organization permits coordination of distributed decision centres and heterarchical consideration confers a partial autonomy to sub-level decision centres. Second, corrective actions against unexpected events are introduced to maintain as far as possible the forecasted scheduling.

A heuristic algorithm for the computation of cyclic schedules and the necessary WIP to obtain optimal cycle time

Presents a heuristic algorithm to determine a cyclic schedule with optimal cycle time while minimizing the work in process (WIP). The respect of the optimal cycle time is a hard constraint during the computation of the schedule, while the minimization of the WIP is considered as an objective. The algorithm builds the schedule progressively and its complexity allows the use under real-time constraints.<<ETX>>

Regulation of a public transport network with consideration of the passenger flow: modeling of the system with high-level Petri nets

In this paper, we present a model of a multimodal public transport network based on high-level Petri nets. This model takes into account both the transport means (bus, tramway, subway, regional train) and the passengers. This model is then simulated in order to measure the impact of the decisions of regulation on the passenger flows.

Synchrony theory applied to control problems in flexible manufacturing systems

Within the synchrony theory, the fairness concept plays an important role in the analysis of conflict resolution in Petri net models. We apply this concept to a class of conflicts in flexible manufacturing systems and develop a simple regulation scheme that ables to integrate constraints on the mean outcome of the conflicts.<<ETX>>

State dependent release control in flexible manufacturing systems

In this paper we address the problem of release control in a flexible manufacturing system subjected to a ratio-respect constraint. We show how this constraint can be included into a product-oriented stochastic Petri-net model and evaluate on an example the effect on the system throughput of the relaxation of an instantaneous ratio-respect constraint. Conflicts are solved according to decision rules and the evaluation is carried our through the calculation of the underlying Markov chain.<<ETX>>

Dynamic Operations Control in Flexible Manufacturing Systems (FMS)

Abstract The problem of combining efficiency and flexibility is the basic challenge faced by flexible manufacturing systems in operating state. A dynamic method for operations control in FMS with job-shop production is proposed using graph theory. Appropriate corrective actions are developed to react to perturbation occuring during production with respect to product due-date. Different states of the manufacturing system are qualified and heuristic programming is introduced to maintain production not far away from outline estimation.

A Mixed-Integer Linear Program for Routing and Scheduling Trains through a Railway Station

This paper studies a train routing and scheduling problem faced by railway station infrastructure managers to generate a conflict-free timetable which consists of two parts, commercial movements and technical movements. Firstly, we present the problem and propose a discrete-time mixed-integer linear mathematical model formulation. Due to the computational complexity of integer programming methods, we need to improve the calculation performance. On one hand, we consider the problem in continuous-time domain which decrease the computational size. The integrality of the scheduling variables is proved. On the other hand, the redundant constraints are cut off by probing the potential conflicts between trains and movements. The full practical problem is large: 247 trains consisting of 503 movements per day should be considered. The proposed approach can solve an instance made of 60 trains and 121 movements representing 385 minutes of traffic within less than 2 minutes.

Supply chain business patterns definition for process interoperability

In the framework of international trading, new regulations are being drawn up concerning safety and in order to prohibit counterfeit goods. Due to the short delays imposed by Customs, the trend is still toward paperless trading. As a consequence, a better process and software interoperability is needed between the different actors of trading (customer, supplier, Customs…); a first step in software interoperability consists in process modeling. This paper presents a pragmatic guideline to generating successfully the business process model. The original aspects are first to use BPMN (Business Process Modeling Notation) for the representation of all types of flows (and not only information flows), and second to propose BPMN business patterns for the international trading purpose.