Application of Tabu Search to Scheduling Trucks in Multiple Doors Cross-Docking Systems

RÉSUMÉ : Cette recherche focus sur l’amélioration des cross-dockings en vue d’augmenter les niveaux de performance du service et de réduire les coûts. l’algorithme de la recherche avec tabous est étudiée pour trouver la séquence optimale d’entrée et sortie des remorques au cross-docking. L’objectif de cette recherche est de maximiser le nombre total de transferts directs entre le fournisseur et une destination finale commune de livraison. Dans les stratégies de distribution actuelles, l’objectif est de synchroniser les chaines du fabricant et du client. Le cross-docking implique de recevoir les produits d’un fournisseur pour plusieurs clients et d’occasionnellement consolider cela avec les produits d’autres fournisseurs pour des destinations finales de livraison communes. En résumé, l’approche examinée dans cette recherche donne une occasion significative pour l’amélioration des opérations au Cross-docking par la réduction du stockage des produits.----------ABSTRACT : Today’s supply chain management performance has been affected by continuously increasing pressure of market forces. The pressure of market includes demands on increased flow of products and throughput with less amount of storage, also customers demand for more products with lower operational costs and more value-added services provided to customers. Supply chain is responsible in cost reduction and service levels increase by providing transshipments across its members. However supply chain has to face fluctuations of demands with the short available lead times. Physical problem of warehouse limitations and also inventory costs and shipping affect the performance of supply chain. In today’s distribution strategies, the main goal is to provide a synchronization of customer chains and the suppliers. The objective is to reduce the inventory buffering between customers and suppliers. The idea of cross-docking is to receive different goods from a manufacturer for several end destinations and possibly consolidate the goods with other manufacturer’s items for common final customers; then ship them in the earliest possible time. The focus of this research effort is to improve cross-dock operations with the goal of increasing the service performance levels and reducing costs. Specifically, metaheuristics algorithm of Tabu search is investigated for finding optimal sequence of incoming and outgoing trailers at cross-docks. This thesis reviews available research literature on cross-dock operations. Tabu search for the truck scheduling problem is presented along with results. Tabu search algorithm is investigated for the truck scheduling problem in the multiple doors cross-docking with unknown incoming and outgoing sequences. The objective of this research is to maximize the total direct transfer of products from a supplier to common final delivery destinations. The algorithm is implemented in C++ and analyzed using different problem instances. The results gained from algorithm of Tabu search are compared with other iterative heuristic descent method. The results indicate that the Tabu search performs significantly better than the descent method for large problem instances. In general, the results present that a metaheuristic algorithm of Tabu search for multiple or single door cross-docking offers thelargest potential for improvement. In summary, the approach explored in this research offers significant opportunity to improve cross-dock operations through reducing storage of products

Heuristics for Truck Scheduling at Cross Docking Terminals

Cross-docking is a logistics management concept that has been gaining global recognition in less-than-truckload logistics industries and retail firms. In cross-docking terminals, shipments are unloaded from inbound trucks at strip doors, consolidated insider cross-docks according to their destinations, and then, loaded into outbound tucks at stack doors. The goal of cross-docking is to reduce inventory and order picking which are the two most costly functions of traditional warehousing management. The sequence in which the inbound and outbound trucks have to be processed at the cross-dock is crucial for improving the efficiency of cross-docking systems. In this thesis we introduce an integer programming formulation and apply four heuristic algorithms: a local search, a simulated annealing, a large neighborhood search and a beam search, to schedule the trucks in a cross-docking terminal so as to minimize the total operational time

Horizontale en verticale samenwerking in distributieketens met cross-docks

Logistiek dienstverleners staan voor grote uitdagingen op het gebied van duurzaamheid, in het bijzonder vanwege de steeds kleiner wordende zendingen die just-in-time bij de klant moeten worden afgeleverd. Samenwerking tussen partners in de distributieketen en met concurrenten daarbuiten biedt kansen om deze uitdagingen het hoofd te bieden. Dit proefschrift richt zich op samenwerkingsvormen in distributieketens met cross-docks. Cross-docks zijn logistieke centra die bedrijven in staat stellen om kleine zendingen gegroepeerd te transporteren zonder dat daarvoor tussentijdse opslag nodig is. In een cross-dock worden goederen direct van inkomende naar uitgaande vrachtwagens verplaatst. Het succesvol toepassen van cross-docking vereist verticale samenwerking tussen partners in opeenvolgende stadia van de distributieketen. Horizontale samenwerking ontstaat tussen mogelijk concurrerende bedrijven die vergelijkbare activiteiten in verschillende distributieketens uitvoeren. Dit proefschrift presenteert theoretische modellen voor horizontale en verticale samenwerking in distributieketens met cross-docks en bestudeert oplossingsmethodieken waarmee de duurzaamheid van deze ketens kan worden verbeterd. Daarvoor worden concepten uit de vakgebieden informatiesystemen, Operations Research en Supply Chain Management gecombineerd. De in dit proefschrift beschreven classificatie van wiskundige cross-docking modellen onthult nieuwe onderzoeksvragen gericht op een betere afstemming tussen interne cross-dock processen en ketenlogistiek. Een simulatiestudie illustreert hoe geringe aanpassingen in de ketenlogistiek tot grote prestatieverbeteringen in het cross-dock leiden. Op het gebied van horizontale samenwerking is een methode ontwikkeld die de uitwisseling van ladingen tussen transporteurs systematiseerd. Een reeks casussen toont aan dat doorbraken in ICT ontwikkeling nodig zijn om samenwerkende transporteurs in staat te stellen gezamenlijk planningsbeslissingen te nemen