Managing Advanced Synchronization Aspects in Logistics Systems

In this thesis, we model various complex logistics problems and develop appropriate techniques to solve them. We improve industrial practices by introducing synchronized solutions to problems that were previously solved independently. The first part of this thesis focuses on cross-docks. We simultaneously optimize supplier orders and cross-docking operations to either reduce the storage space required or evenly distribute workload over the week. The second part of this thesis is devoted to transport problems in which two types of vehicles are synchronized, one of which can be transported by the other. The areas of application range from home services to parcel delivery to customers. After analyzing the complexity associated with these synchronized solutions (i.e., largescale problems for which the decisions depend on each other), we design algorithms based on the "destroy-and-repair" principle to find efficient solutions. We also introduce mathematical programs for all the considered problems. The problems under study arose directly from collaborations with various industrial partners. In this respect, our achieved solutions have been benchmarked with current industrial practice. Depending on the problem, we have been able to reduce the environmental impact generated by the industrial activities, the overall cost, or the social impact. The achieved gains compared to current industrial practice range from 10 to 70%, depending on the application. -- Dans cette thèse, nous modélisons divers problèmes logistiques complexes et développons des techniques appropriées pour les résoudre. Nous cherchons à améliorer certaines pratiques industrielles en introduisant des solutions synchronisées à des problèmes qui étaient auparavant résolus indépendamment. La première partie de cette thèse porte sur les cross-docks. Nous optimisons simultanément les commandes fournisseurs et les opérations au sein de la plateforme de logistique pour réduire l’espace de stockage requis ou répartir uniformément la charge de travail sur la semaine. La deuxième partie de cette thèse est consacrée aux problèmes de transport dans lesquels deux types de véhicules sont synchronisés, l’un pouvant être transporté par l’autre. Les domaines d’application vont du service à domicile à la livraison de colis chez des clients. Après avoir analysé la complexité des solutions synchronisées (c’est-à-dire des problèmes de grandes dimensions pour lesquels les décisions dépendent les unes des autres), nous concevons des algorithmes basés sur le principe de "destruction / reconstruction" pour trouver des solutions efficaces. Nous modélisons également les problèmes considérés avec la programmation mathématique. Les problèmes à l’étude viennent de collaborations avec divers partenaires industriels. A cet égard, les solutions que nous présentons sont comparées aux pratiques industrielles actuelles. En fonction du problème, nous avons pu réduire l’impact environnemental généré par les activités industrielles, le coût global, ou l’impact social des solutions. Les gains obtenus par rapport aux pratiques industrielles actuelles varient de 10 à 70%, selon l’application. Mot-clefs: Logistique, Synchronisation, Problème de transport, Tournée de véhicules, Plateforme de Cross-dock (transbordement), Programmation Mathématiques, Métaheuristiques, Matheuristiques, Instances Réelle

Parcel delivery cost minimization with time window constraints using trucks and drones

We propose a model for solving a parcel delivery problem with a fleet of trucksembedded with drones. When appropriate, drones are loaded with a parcel, launcheddirectly from the truck, and sent to a client. Afterward, the drones autonomouslyreturn to the truck to be replenished and recharged. Inspired by the case of a largeEuropean logistics provider, the proposed modeling framework confronts realis-tic delivery problems involving time windows, limited drone autonomy, and theeligibility of clients to be served by drones. The considered global cost functionincludes fixed daily vehicle fares, driver wages, and the fuel and electricity con-sumption to power trucks and drones. To solve the problems at hand, we proposea mixed-integer linear programming formulation and an adaptive large neighbor-hood search. Moreover, we introduce an efficient modeling framework to managethe numerous synchronization constraints induced by the simultaneous use of trucksand drones. We analyze the benefits of this new transportation concept for deliveryproblems involving up to 100 parcels. Results show that truck-and-drone solutionscan reduce costs up to 34% compared to traditional truck-only delivery. From a man-agerial perspective, we show that a certain percentage of client locations must bereachable by drone to make truck-and-drone solutions competitive (i.e., if the fixedcosts of the drones are compensated for by the savings on truck routes) and comparethe cost structures of truck-and-drone versus truck-only solution

Vehicle routing with transportable resources: using carpooling and walking for on-site services

In the classical Vehicle Routing Problem (VRP), it is assumed that each worker moves using an individually assigned vehicle. Removing this core hypothesis opens the door for a brand new set of solutions, where workers are seen as transportable resources that can also move without the help of a vehicle. In this con- text, motivated by a major European energy provider, we consider a situation where workers can either walk or drive to reach a job and where carpooling is enabled. In order to quantify the potential benefits offered by this new framework, a dedicated Variable Neighborhood Search is proposed to efficiently tackle the underlying synchronization and precedence constraints that arise in this extension of the VRP. Con- sidering a set of instances in an urban context, extensive computational experiments show that, despite conservative scenarios favoring car mobility, significant savings are achieved when compared to the solu- tions currently obtained by the involved company. This innovative formulation allows managers to reduce the size of the vehicle fleet while keeping the number of workers stable and, surprisingly, decreasing the overall driving distance simultaneously

Multi-modal variations of the vehicle routing problem, proceedings of the 1st informs conference of the transportation science & logistics society

In this work, we extend the Vehicle Routing Problem formulation by proposing multi-modal variations of this well-established problem. For these new formulations, we empirically show that a streamline metaheuristic is able to highlight the potential benefit offered by the introduction of multi-modality