Thirty years of heterogeneous vehicle routing

It has been around thirty years since the heterogeneous vehicle routing problem was introduced, and significant progress has since been made on this problem and its variants. The aim of this survey paper is to classify and review the literature on heterogeneous vehicle routing problems. The paper also presents a comparative analysis of the metaheuristic algorithms that have been proposed for these problems

Algorithms for vehicle routing problems with heterogeneous fleet, flexible time windows and stochastic travel times

Orientador: Vinícius Amaral ArmentanoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Este trabalho aborda três variantes multiatributo do problema de roteamento de veículos. A primeira apresenta frota heterogênea, janelas de tempo invioláveis e tempos de viagem determinísticos. Para resolvê-la, são propostos algoritmos ótimos baseados na decomposição de Benders. Estes algoritmos exploram a estrutura do problema em uma formulação de programação inteira mista, e três diferentes técnicas são desenvolvidas para acelerá-los. A segunda variante contempla os atributos de frota heterogênea, janelas de tempo flexíveis e tempos de viagem determinísticos. As janelas de tempo flexíveis permitem o início do serviço nos clientes com antecipação ou atraso limitados em relação às janelas de tempo invioláveis, com custos de penalidade. Este problema é resolvido por extensões dos algoritmos de Benders, que incluem novos algoritmos de programação dinâmica para a resolução de subproblemas com a estrutura do problema do caixeiro viajante com janelas de tempo flexíveis. A terceira variante apresenta frota heterogênea, janelas de tempo flexíveis e tempos de viagem estocásticos, sendo representada por uma formulação de programação estocástica inteira mista de dois estágios com recurso. Os tempos de viagem estocásticos são aproximados por um conjunto finito de cenários, gerados por um algoritmo que os descreve por meio da distribuição de probabilidade Burr tipo XII, e uma matheurística de busca local granular é sugerida para a resolução do problema. Extensivos testes computacionais são realizados em instâncias da literatura, e as vantagens das janelas de tempo flexíveis e dos tempos de viagem estocásticos são enfatizadasAbstract: This work addresses three multi-attribute variants of the vehicle routing problem. The first one presents a heterogeneous fleet, hard time windows and deterministic travel times. To solve this problem, optimal algorithms based on the Benders decomposition are proposed. Such algorithms exploit the structure of the problem in a mixed-integer programming formulation, and three algorithmic enhancements are developed to accelerate them. The second variant comprises a heterogeneous fleet, flexible time windows and deterministic travel times. The flexible time windows allow limited early and late servicing at customers with respect to their hard time windows, at the expense of penalty costs. This problem is solved by extensions of the Benders algorithms, which include novel dynamic programming algorithms for the subproblems with the special structure of the traveling salesman problem with flexible time windows. The third variant presents a heterogeneous fleet, flexible time windows and stochastic travel times, and is represented by a two-stage stochastic mixed-integer programming formulation with recourse. The stochastic travel times are approximated by a finite set of scenarios generated by an algorithm which describes them using the Burr type XII distribution, and a granular local search matheuristic is suggested to solve the problem. Extensive computational tests are performed on instances from the literature, and the advantages of flexible windows and stochastic travel times are stressed.DoutoradoAutomaçãoDoutor em Engenharia Elétrica141064/2015-3CNP

Multi-Agent Systems for Transportation Planning and Coordination

Many transportation problems are in fact coordination problems: problems that require communication, coordination and negotiation to be optimally solved. However, most software systems targeted at transportation have never approached it this way, and have instead concentrated on centralised optimisation. Multi-agent systems (MAS) are a different approach to building software systems. Such systems are assembled from autonomously interacting agents; agents are small software programs, which have some type of intelligence and individual behaviour. Communication and coordination (between agents) are the essential elements in the construction of MAS. The transportation domain is often referred to as a potential candidate for the application of MAS. In this dissertation, we discuss two MAS design cases related to the transport of containers. Both cases resulted in concrete prototypes, which let us evaluate a series of aspects important in applying MAS in transportation. We demonstrate the importance of a multi-method validation and evaluation approach. The prototypes were furthermore utilised as artefacts to discuss eventual implementation with future users and experts. One of our most important observations is that planning, as a function within supply chains, is about to go through a fundamental change. Like the mobile phone changed the way people coordinate in daily life, the concepts discussed in this dissertation have the potential to fundamentally change coordination in supply chains. As part of this fundamental change, a different perspective on certainty and uncertainty is essential

Optimización en sistemas multi-robot mediante embodied evolution

Programa Oficial de Doutoramento en Computación. 5009V01[Resumen] En esta tesis se ha desarrollado una versión del algoritmo evolutivo Embodied Evolution (EE) que generaliza las existentes en el campo, con el objetivo de avanzar en la estandarización de este paradigma de forma que pueda ser estudiado de manera formal, y así conocer sus fortalezas y limitaciones. El algoritmo desarrollado en esta tesis se ha denominado “canónico”porque se ha diseñado tras el análisis detallado de los procesos básicos comunes a las diferentes variantes dentro de Embodied Evolution, de modo que únicamente contiene dichos procesos intrínsecos, y una parametrización de los mismos lo más general posible. El funcionamiento de este algoritmo can´onico de Embodied Evolution se ha analizado en un conjunto de funciones teóricas representativas de los espacios de búsqueda en optimización colectiva, sobre los que se ha llevado a cabo un análisis de sensibilidad exhaustivo. Finalmente, las conclusiones del análisis teórico se han validado en una tarea real en la cual se ha podido comprobar la validez de la aproximación a la hora de optimizar la coordinación emergente del sistema multi-robot, tanto a nivel de rendimiento como a nivel de organización automática en especies, una propiedad fundamental de este paradigma.[Resumo] Nesta tese doutoral desenvolveuse unha version do algoritmo evolutivo Embodied Evolution (EE) que xeneraliza as existentes no campo, co obxectivo de avanzar na estandarización deste paradigma, de forma que poida ser estudado de maneira formal, e así coñecer as súas fortalezas e limitacións. O algoritmo desenvolvido nesta tese denominouse algoritmo canónico porque foi deseñado tras analizar detalladamente os procesos básicos comúns ás diferentes variantes dentro de Embodied Evolution, de modo que únicamente contén estes procesos intrínsecos, e una parametrización dos mesmos o máis xeral posible. O funcionamiento do algoritmo canónico de Embodied Evolution analizouse nun conxunto de funcións teóricas representativas dos espazos de búsqueda en optimización colectiva, sobre os que se realizou unha análise de sensibilidade exhaustiva. Finalmente, as conclusions da análise teorica validouse nunha tarefa real, na que se puido comprobar a validez da aproximación á hora de optimizar a coordinación emerxente do sistema multi-robot, tanto a nivel de rendemento como a nivel de organización automática en especies, unha propiedade fundamental neste paradigma.[Abstract] In this PhD thesis, a version of the Embodied Evolution (EE) algorithm has been developed that generalizes the existing version on the field, with the goal of advancing in the standardization of this paradigm such that it could be studied in a formal way and discover its strengths and limitations. The developed algorithm has been named “canonical” because it was designed after analyzing in detail the basic common processes of the di↵erent variants in Embodied Evolution, in a way that only contains the intrinsic processes and a parametrization as general as possible. The operation of this Embodied Evolution canonical algorithm has been analyzed in a set of theoretic functions that represent the di↵erent search landscapes in collective optimization, in which a sensibility analysis has been performed. Finally, the conclusions of the theoretic analysis has been validated in a real task in which the validity of the approximation has been confirmed through the successful optimization of the emergent coordination of the multi-robot system, both in performance and in automatic organization in species, a fundamental property in this paradigm

Swarm Robotics

Collectively working robot teams can solve a problem more efficiently than a single robot, while also providing robustness and flexibility to the group. Swarm robotics model is a key component of a cooperative algorithm that controls the behaviors and interactions of all individuals. The robots in the swarm should have some basic functions, such as sensing, communicating, and monitoring, and satisfy the following properties

Digital Earth: The Impact of Geographic Technology Through the Ages

Geographic technology encompasses a wide range of geographic knowledge, concepts, processes, and artifacts. Because of its interdisciplinarity and integration with other technologies, the paper examines the diffuse impacts of geographic technology within the evolving relationship between technological and societal developments over time