ghassen cherif - Profile on Academia.edu (original) (raw)

Papers by ghassen cherif

Scheduling Problems for a Class of Hybrid FMS Using T-TPN and Beam Search

Journal of Control, Automation and Electrical Systems, Mar 3, 2021

This paper is about scheduling problems for a class of flexible manufacturing systems (FMS) that ... more This paper is about scheduling problems for a class of flexible manufacturing systems (FMS) that have some operations with total precedence constraints and other operations with full routing flexibility (namely hybrid FMS). The objective is to find a control sequence from an initial state to a reference one in minimal time. For that, a systematic multi-level formalism is introduced to model the hybrid FMS based on the hierarchical structuration of the operations. Transition-timed Petri nets (T-TPN) that behave under earliest firing policy are used for that purpose. Then a new cost function is introduced to estimate the residual time to the reference. This estimation is proved to be a lower bound of the true duration. A modified Beam Search algorithm is proposed that uses the cost function to selectively explore the Petri net (PN) state space. Computational experiments illustrate the efficiency of the approach in comparison with other existing methods.

Journal of Intelligent Manufacturing, Aug 25, 2021

In this paper, incremental computation of schedules for complex discrete event systems in an unce... more In this paper, incremental computation of schedules for complex discrete event systems in an uncertain environment is studied. Uncertainties are assumed to occur due to uncontrollable events. A particular class of flexible manufacturing systems (FMSs) with partial precedence constraints is proposed where some operations are performed with total precedence constraints and others with full routing flexibility (namely partial routing FMSs). Interruptions may occur due to unavailability of resources and interruption of operations. Such interruptions may deviate the trajectory from the planed schedule. For the modeling of the partial routing FMS, a systematic multi-level formalism based on the hierarchical structuration of the operations is introduced. Then, the risk of deviation is integrated and a new cost function is defined accordingly. Finally, a modified beam search algorithm referred to as generation double filtered beam search algorithm that accelerates the convergence of the method is proposed. The new algorithm is based on a new filtering mechanism that uses the cost function to selectively explore the state space of Petri net model in order to find a control sequence from an initial state to a reference one with a trade-off between performance and robustness. Examples are used to illustrate the efficiency of the proposed scheduling approach.

Modelling and Optimization Approaches for Advanced Manufacturing Systems

Proceedings of the 2023 10th International Conference on Industrial Engineering and Applications

Modeling and routing problems of automated port using T-TPN and Beam search

2022 8th International Conference on Control, Decision and Information Technologies (CoDIT)

Scheduling of hybrid workshops in uncertain environment

Cette thèse concerne les problèmes d'ordonnancement pour une classe de systèmes manufacturier... more Cette thèse concerne les problèmes d'ordonnancement pour une classe de systèmes manufacturiers flexibles (FMS) en environnement incertain. Les systèmes considérés répondent aux exigences de l’industrie 4.0 qui requièrent des organisations plus agiles permettant de proposer des produits personnalisés. Plus précisément, les systèmes proposés dans ce travail sont appelés FMS hybrides et traitent les opérations avec des contraintes de précédence partielles entre les opérations. La première contribution est une approche systématique de modélisation des FMS hybrides avec les réseaux de Petri temporisés sur les transitions (T-TPN) et un formalisme multi-niveaux basé sur la structuration hiérarchique des opérations. La deuxième contribution concerne la recherche d’ordonnancements pour les FMS hybrides. Nous utilisons la recherche en faisceau et proposons une fonction coût basée sur la modélisation multiniveaux. Nous proposons également une nouvelle variante de la recherche en faisceau, ...

Generation Filtered Beam Search algorithm for the scheduling of hybrid FMS using T-TPN

2019 18th European Control Conference (ECC), 2019

This paper is about the incremental computation of control sequences for complex discrete event s... more This paper is about the incremental computation of control sequences for complex discrete event systems (DES). Transition-timed Petri nets (T-TPNs) that behave under earliest firing policy are used to model hybrid FMS that has some operations with total precedence constraints and other operations with full routing flexibility. The objective is to find a control sequence from an initial state to a reference one in minimal time. For that, a cost function is proposed and used with a new variant of beam search method that selectively explores the PN state space.

Ordonnancement dans les ateliers hybrides en environnement incertain. (Scheduling of hybrid workshops in uncertain environment)

Hybrid FMS scheduling using T-TPN and Beam Search in uncertain environments

IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society

Modeling hybrid manufacturing systems using T-TPN with buffers

2018 IEEE 23rd International Conference on Emerging Technologies and Factory Automation (ETFA)