1,720,992 research outputs found
A note on the complexity of the picker routing problem in multi-block warehouses and related problems
No full textThe Picker Routing Problem (PRP), which consists of finding a minimum-length tour between a set of storage locations in a warehouse, is one of the most important problems in the warehousing logistics literature. Despite its popularity, the tractability of the PRP in multi-block warehouses remains an open question. This technical note aims to fill this research gap by establishing that the problem is strongly NP-hard. As a corollary, the complexity status of other related problems is settled
Vehicle routing problems with multiple trips
No full textThis paper presents a survey on the multi-trip vehicle routing problem (MTVRP) and on related routing problems where vehicles are allowed to perform multiple trips. The first part of the paper focuses on the MTVRP. It gives an unified view on mathematical formulations and surveys exact and heuristic approaches. The paper continues with variants of the MTVRP and other families of routing problems where multiple trips are sometimes allowed. For the latter, it specially insists on the motivations for having multiple trips and the algorithmic consequences. The expected contribution of the survey is to give a comprehensive overview on a structural property of routing problems that has seen a strongly growing interest in the last few years and that has been investigated in very different areas of the routing literature
The storage location assignment and picker routing problem: A generic branch-cut-and-price algorithm
Full text linkThe Storage Location Assignment Problem (SLAP) and the Picker Routing Problem (PRP) have received significant attention in the literature due to their pivotal role in the performance of the Order Picking (OP) activity, the most resource-intensive process of warehousing logistics. The two problems are traditionally considered at different decision-making levels: tactical for the SLAP, and operational for the PRP. However, this paradigm has been challenged by the emergence of modern practices in e-commerce warehouses, where decisions are more dynamic. This shift makes the integrated problem, called the Storage Location Assignment and Picker Routing Problem (SLAPRP), pertinent to consider. Scholars have investigated several variants of the SLAPRP, including different warehouse layouts and routing policies. Nevertheless, the available computational results suggest that each variant requires an ad-hoc formulation. Moreover, achieving a complete integration of the two problems, where the routing is solved optimally, remains out of reach for commercial solvers, even on trivial instances. In this paper, we propose an exact solution framework that addresses a broad class of variants of the SLAPRP, including all the previously existing ones. This paper proposes a Branch-Cut-and-Price framework based on a novel formulation with an exponential number of variables, which is strengthened with a novel family of non-robust valid inequalities. We have developed an ad-hoc branching scheme to break symmetries and maintain the size of the enumeration tree manageable. Computational experiments show that our framework can effectively solve medium-sized instances of several SLAPRP variants and outperforms the state-of-the-art methods from the literature
The Multi-Trip Vehicle Routing Problem with Time Windows and Release Dates
No full textThe multi-trip vehicle routing problem with time windows and release dates is a variant of the multi-trip vehicle routing problem where a time window and a release date are associated with each customer. The release date represents the date when the merchandise requested by a customer becomes available at the depot. The interest for this problem comes from the field of city logistics and the study of delivery systems involving City Distribution Centers (CDC). In these systems, goods are first delivered to a CDC before being transferred to eco-friendly vehicles for final delivery. We propose to address the problem through a population-based algorithm, with a giant tour representation for individuals. An efficient labeling procedure allows turning giant tours into solutions. Experiments demonstrate the effectiveness of the method
Optimization of human-aware logistics and manufacturing systems: A survey on the Human-Aware Models
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Vehicle routing problems for city logistics
No full textThis paper surveys the vehicle routing problems met in cities for good distribution. It applies the following methodology. First, it gives an overview of the literature devoted to vehicle route optimization in cities. Then, it classifies and analyses urban logistic flows. As a result, it identifies the principal scientific challenges that need to be addressed: time-dependency, multi-level and multi-trip organization of the distribution, dynamic information. Finally, it focuses on each one of these challenges, analyses the main difficulties they imply and how they are treated in the literature
Simulation of Mutualized Urban Logistics Systems with Real-time Management
No full textThis work aims at proposing a new organization of urban merchandize distribution based on mutualized and optimized resources. In this context, our contribution is twofold. On one hand, we develop a set of models to manage merchandize distribution. We develop a new reservation system that enables customers to request a merchandize transportation service (delivery and collect) or to book a vehicle for self-service purposes. Requests are processed by two main decision modules (1) an online module that immediately searches for a feasible solution for a request, and decides to accept or reject it, and (2) an offline module that looks for optimized solutions starting from the feasible schedule defined by the online module. On the other hand, we develop a new discrete event simulator, called MODUMS which integrates the proposed models, implements such a logistic system and evaluates its economic and environmental impact. MODUMS takes as inputs realistic information about the transportation means, geographic data and demand information requests that are generated according to some probability distributions. It gives as outputs indicators on the impact of mutualization on the quality of urban logistics in terms of, for example, number of delayed or rejected requests, filling rate of vehicles, total distance and quantity of CO2
Two-echelon distribution with a single capacitated hub
No full textIn this paper, we investigate the synchronization between the two echelons in two-echelon urban distribution systems. The first echelon aims at transferring goods from a warehouse to a (single) city hub located in the city center. The second echelon, managed with a fleet of environmentally friendly vehicles, delivers goods to final customers, from the city hub. The two echelons are synchronized in time but also with regards to the capacity of the city hub. As far as we know, this is the first study considering the latter issue in the context of two-echelon distribution. To deal with the synchronization while optimizing the distribution, we propose a three-phase heuristic solution approach. At first, our approach optimizes the distribution for the second echelon. Then, it manages the synchronization. Finally, it optimizes the distribution for the first echelon. Population-based metaheuristics and integer programs are used. Results show the effectiveness of the method and permit to derive managerial insights on the distribution
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