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Scheduling handling resources: robotic flowshops with circular layout and a practical railway problem

Florence Thiard 1
1 G-SCOP_ROSP [2016-2019] - Recherche Opérationnelle pour les Systèmes de Production [2016-2019]
G-SCOP - Laboratoire des sciences pour la conception, l'optimisation et la production
Abstract : The first part of this work deals with cyclic production for throughput optimization in robotic flow-shops, where a robot is in charge of the material handling of parts. Robotic cells may have a linear or a circular layout. Most theoretical results for the linear layout do not hold for the circular layout. In particular, the problem of finding the best one part production cycle (1-cycle), which is a polynomial problem for linear additive cells, has been proved NP-hard for the corresponding circular configuration. We mainly focus on a special case of circular balanced cells, where the processing times are identical for all machines. After presenting tools for cyclic analysis in circular cells, we study necessary properties of efficient 1-cycles. These results allow to conclude on the best one part production cycle for any parameters in circular balanced cells up to 8 machines. However, we provide a counter-example to the classical 1-cycle conjecture, still open for this configuration. Then, we study the structure of efficient one part production cycles in arbitrarily large circular balanced cells. We introduce and study a new family of cycles based on this structure, and formulate a conjecture on its dominance over one part-production cycles, which would lead to a polynomial algorithm for finding the best 1-cycle for circular balanced cells. This structure allows to settle the best one part production cycle for cells with up to 11 machines. In a second part, we present work on an industrial problem of railway stock scheduling proposed by the French railway company in the context of the ROADEF/EURO competition. We propose a greedy algorithm for this problem combining the various aspects of trains handling inside a station.
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Florence Thiard. Scheduling handling resources: robotic flowshops with circular layout and a practical railway problem. Operations Research [cs.RO]. Université Grenoble Alpes, 2017. English. ⟨tel-01707522v2⟩

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