Spelling suggestions: "subject:"mixedinteger linear programming"" "subject:"biginteger linear programming""
81 |
Régulation adaptative multi-objectif et multi-mode aux carrefours à feux / Multi-objective and multi-mode adaptive traffic control on signal-controlled junctionsDujardin, Yann 24 June 2013 (has links)
Afin de répondre à la problématique de la régulation multi-objectif et multi-mode des carrefours à feux, nous proposons trois modèles de programmation linéaire mixte en nombres entiers constituant les moteurs d'un système de régulation pleinement adaptatif, ainsi que deux procédures interactives d'optimisation multi-objectif permettant d'adapter itérativement une “politique de régulation” à la situation de trafic. Les critères pris en compte, tous à minimiser, sont le temps d'attente et le nombre d'arrêts des véhicules particuliers, et un critère dédié aux transports en commun permettant de fixer un temps d'attente souhaité pour chaque bus. Des expérimentations ont montré qu'un des trois modèles, dit hybride, se démarque positivement des deux autres. Ce modèle a alors été mis en œuvre avec une des deux procédures interactives, permettant de contrôler un trafic simulé sur une période d'une heure dans différents scénarios types, et comparé à un système de régulation semi-adaptatif. / In order to answer the multi-objective and multi-mode adaptive traffic control problem, we propose three models of mixed integer linear programming, usable with two multi-objective optimization interactive methods, allowing to adapt a “traffic control policy” iteratively to the current traffic situation. The considered criteria, all of them to be minimized, are the total waiting time and the number of stops for private vehicles and a criterion dedicated to public transports allowing to set a target waiting time for every bus. Experiments showed that one of the three models, called hybrid model, distinguishes itself positively from the others. This model was implemented with one of the two interactive methods, allowing to control a traffic simulated over one hour in different scenarios, and was compared to a semi-adaptive traffic control system.
|
82 |
OPTIMISATION DU PLAN DE TRANSPORT PAR PLANIFICATION INTEGREE DES RESSOURCES / INTEGRATED PLANNING OF RAILWAY TRANSPORTATION RESOURCESBenhizia, Faten 25 October 2012 (has links)
La production des circulations ferroviaires a la sncf repose actuellement sur un processus essentiellement sequentiel dans lequel la conception des grilles horaires de circulation (reservation de l'infrastructure pour la circulation des trains de l'offre de transport de la sncf) conditionne largement la conception des planifications des engins ferroviaires (les roulements engins), puis celle des agents de conduite (adc) (les grilles de service des adc). cette strategie de planification sequentielle des ressources ferroviaires a ete massivement adoptee pour des raisons pratiques et scientifiques (historique, savoir-faire, complexite du systeme ferroviaire, etc.). toutefois, cette strategie de planification sequentielle genere des solutions qui peuvent etre de cout eleve et moins robustes aux aleas, car les decisions prises a une etape donnee peuvent reduire considerablement l'ensemble des solutions realisables aux etapes suivantes. face a ce constat et a la forte interaction entre ces trois ressources heterogenes et tres couteuses, la sncf a souhaite investiguer la praticabilite et les apports d'une demarche d'optimisation du plan de transport par planification integree de ces ressources critiques. dans cette optique, les travaux de these ont porte sur l'etude de faisabilite, le prototypage et la validation d'une demarche de planification integree des ressources permettant d'ameliorer l'efficacite globale du plan de transport, d'accroitre la competitivite de la sncf et d'ameliorer la qualite de ses services. nous avons propose une formalisation du probleme de planification integree engins/adc et des algorithmes performants qui s'appuient sur une approche par relaxation lagrangienne pour resoudre de maniere efficace la problematique etudiee. cette approche repose sur l'exploitation de deux briques logicielles developpees a la sncf pour resoudre chacun des sous-problemes de planification des engins et des adc. les algorithmes ont ete testes experimentalement avec des donnees reelles de la region ter bretagne. differentes evolutions des modeles et des algorithmes ont ete etudiees pour rendre ces derniers plus efficaces. les tests de validation sur des jeux de donnees reelles a une echelle industrielle sont encourageants et montrent des gains potentiels allant jusqu'a 4% des adc exploites par rapport a une approche traditionnelle (sequentielle). / The planning of railway production at the french national railways (sncf) is currently based on a mainly sequential process in which the design of railway timetabling widely conditioning design planning of railway equipment (rolling stock), then one of the train drivers (driver rosters). this strategy of sequential planning of railway resources massively adopted for practical and scientific reasons (expertise, complexity of the railway system, etc.). however, this strategy generates solutions which can be more expensive and less robust to uncertainties, because decisions taken at any given stage can significantly reduce the overall feasible solutions of the following steps.given this situation and the strong interaction between these heterogeneous and very expensive resources, the thesis deals with the feasibility and inputs of a process where these critical resources could be planned and optimized in an integrated way. the thesis focuses on the feasibility study, prototyping and validation of an integrated approach for planning rolling stocks and drivers, so as to improve the efficiency of the overall transportation plan, increase sncf competitiveness and enhance the quality of its services. we propose a mixed integer linear programming formulation of the rolling stock/ train drivers integrated planning problem. in this mathematical model, each planning sub-problem is formalized and coupling constraints are further introduced to model the interdependencies of these two resources when they are simultaneously used for train production. in this heuristic, the solution of the lagrangian dual and the calculation of feasible solutions are performed by calling two proprietary software modules available at sncf for planning rolling stocks and train drivers. the heuristic is tested experimentally with real data from the ter bretagne region, and several evolutions are introduced in the models and algorithms so as to improve their performances.validation tests on of real data sets at an industrial scale are encouraging and, when compared to a traditional (sequential) approach, show gain of up to 4% for train drivers used.
|
83 |
Técnicas de pesquisa operacional aplicadas ao problema de programação de cirurgias eletivas. / Operational research techniques applied to the elective surgeries scheduling problem.Hortencio, Hanna Pamplona 20 May 2019 (has links)
Atualmente, os hospitais se veem obrigados a melhorar sua produtividade. Os centros cirúrgicos, além de ser um dos setores com maiores custos, também é o que mais gera receita dentro de um hospital, dessa forma torna-se extremamente importante o gerenciamento eficiente desse setor. Os métodos de otimização para programação de cirurgias podem ser usados como ferramentas para reduzir filas e ociosidade nos centros cirúrgicos, aumentando sua produtividade. O Problema de Programação de Cirurgias Eletivas com Múltiplos Recursos e Múltiplas Etapas consiste em alocar os recursos às etapas do processo cirúrgico dos pacientes, considerando as diferentes necessidades e rotas de cada paciente e, então, programar essas etapas no tempo respeitando a disponibilidade dos recursos e a sequência das etapas do processo cirúrgico dos pacientes. Esse problema é classificado na literatura como NP-hard e pode ser descrito como um Job Shop Flexível com blocking e função objetivo de minimização do número de pacientes não atendidos e do instante de término da última etapa, o makespan. O Objetivo desse trabalho é propor um modelo matemático e uma heurística construtiva para a resolução desse problema. O modelo matemático Multi-Mode Blocking Job Shop (MMBJS) apresentado em Pham e Klikert (2008) é explorado e algumas melhorias são apontadas neste trabalho. Um modelo matemático de Programação Linear Inteira Mista alternativo é proposto, a fim de reduzir o esforço computacional, ajustar o cálculo do makespan e sugerir uma estratégia de priorização de pacientes. Testes computacionais foram realizados, afim de comparar o modelo MMJBS e o modelo proposto. Para instâncias em que todos os pacientes são atendidos, as soluções encontradas pelo CPLEX para ambos modelos são iguais, porém o tempo computacional necessário para encontrar uma solução ótima é em média 45% menor no modelo proposto. Também foram realizados testes computacionais com objetivo de observar o comportamento do modelo com diferentes configurações de recursos. Para instâncias com 15 pacientes, os testes apontam que o tempo computacional para encontrar a solução ótima é superior a 2h de processamento. Dessa forma, uma heurística construtiva é proposta, com objetivo de gerar soluções factíveis com pouco esforço computacional. A heurística proposta aloca cada etapa do tratamento de cada paciente aos recursos necessários, respeitando as janelas de disponibilidade dos recursos e buscando reduzir a folga no sistema. Um exemplo de aplicação da heurística construtiva é apresentado. As propostas para trabalhos futuros são apresentadas no capítulo final desta dissertação. / For the past few years, hospitals have been forced to improve their productivity, with surgical centers being one of the sectors with higher costs within such organizations, but also the ones that generate the most revenue. Thus, optimization methods for surgical programming are tools that can be used to reduce queues and idleness in these sectors and consequently achieve the aforementioned goals. The \"Problem of Programming Multiple Surgical Resources with Multiple Steps\"consists in allocating the existing resources to each surgery stage that a patient will need to go through, considering the different needs, sequence and specificities of each of them, and then scheduling these steps in time. This type of problem is classified in the current literature as an NP-hard problem, being described as a Flexible Job Shop with blocking and an objective function that seeks to minimize the number of patients not served and the total makespan. The general purpose of this research is to propose a mathematical model and a constructive heuristic for this type problem. The proposed model explores the mathematical model Multi-Mode Blocking Job Shop (MMBJS) presented in Pham and Klikert (2008) suggesting improvements through the use of an alternative Mixed Integer Linear Programming that aims to: reduce the computational effort, adjust the makespan calculation and suggest a strategy of patients prioritization. In order to prove the benefits of the proposed enhancements, computational tests were performed to compare the MMJBS model and the proposed model, identifying that for instances where in which all patients are attended, the solutions found by CPLEX for both models are the same, but with a lower computational time the proposed model (45% average reduction). Also, other computational tests were performed to observe the behavior of the model with different configurations of resources. For instances with 15 patients, the tests indicate that the computational time to find the optimal solution is greater than 2 hours of processing. Thus a constructive heuristic is proposed, it aims to generate feasible solutions with little computational effort. The proposed heuristic allocates each surgery stage of a patient to the necessary resources, respecting the available windows and seeking to reduce the total slack in the system. An example of the application of the constructive heuristic is also presented. At last, future works proposals are presented in the final chapter of this dissertation.
|
84 |
Problema de roteamento de veículos com frota mista, janelas de tempo e custos escalonados. / Fleet size and mix vehicle routing problem with time windows and scaled costs.Manguino, João Luiz Veiga 18 February 2013 (has links)
O tema de roteamento de veículos é de grande importância na literatura e tem sido amplamente estudada pela sua importância para muitas indústrias. Com a evolução na literatura, mais características foram adicionadas para torná-lo mais próximo de situações reais. Alinhado com esta tendência, este trabalho aborda o problema de roteamento de veículos quando há a terceirização da frota que realiza as entregas. Uma forma de cobrança do frete é por meio de custos escalonados, que são calculados de acordo com o tipo de veículo e a distância percorrida, com valores fixos para cada faixa de distância. Embora seja uma forma comum de trabalho na indústria, nenhum trabalho focado nesta característica foi encontrado na literatura. Este problema é o problema de roteamento de veículos com frota mista, janelas de tempo e custos escalonados (FSMVRPTWSC). Ao abordar este problema, este trabalho apresenta um modelo de programação linear inteira mista que é avaliado em um cenário real da indústria. Além disso, três heurísticas de inserção sequencial são propostas para lidar com problemas maiores. Estes métodos são examinados por meio de testes computacionais em 168 problemas de referência gerados para este problema. Os experimentos numéricos mostram que os métodos são robustos e eficientes, apresentando um bom desempenho em conjuntos de problemas com diversas características. / The theme of vehicle routing is of great importance in the literature and has been widely studied for its relevance to many industries and, throughout the literature, more characteristics have been added to make it closer to real situations. Aligned with this trend, this paper addresses the vehicle routing problem when there is outsourcing of the fleet that delivers goods. One form of freight charging is by scaled costs, which are calculated according to the type of vehicle and the distance traveled, with fixed values for each distance range. Though it is a common form of work in the industry, no work focused on this characteristic was found in the literature. This problem is the fleet size and mix vehicle routing problem with time windows and scaled costs (FSMVRPTWSC). In approaching this problem, this paper presents a mixed integer linear programming model that is evaluated under a real situation scenario. Furthermore, three sequential insertion heuristics are proposed in order to deal with larger problems. These methods are examined through a computational comparative study in 168 benchmark problems generated for this problem. The numerical experiments show that the methods are robust and efficient, performing well in different problem sets.
|
85 |
Placement des tâches matérielles de tailles variables sur des architectures reconfigurables dynamiquement et partiellement / Placement of Variable-sized Hardware Tasks on dynamically and partially reconfigurable architecturesHannachi, Marwa 20 December 2017 (has links)
Les systèmes adaptatifs basés sur les architectures FPGA (Field-Programmable Gate Arrays) peuvent bénéficier grandement de la grande flexibilité offerte par la reconfiguration partielle dynamique (DPR). Grâce au DPR, les tâches matérielles composant un système adaptatif peuvent être allouées et re-allouées à la demande ou en fonction de l'environnement dynamique. Les flots de conceptions disponibles et les outils commerciaux ont évolué pour répondre aux exigences des architectures reconfigurables qui sont toutefois limitées dans leurs fonctionnalités. Ces outils ne permettent pas un placement et une relocation efficaces de tâches matérielles de tailles variables. L'objectif principal de ces travaux de thèse consiste à proposer des nouvelles méthodologies et de nouvelles approches pour faciliter au concepteur la phase de conception d'un système adaptatif reconfigurable opérationnelle, valide, optimisé et adapté aux changements dynamiques de l'environnement. La première contribution de cette thèse porte sur la problématique de la relocation des tâches matérielles de tailles différentes. Une méthodologie de conception est proposée pour répondre à un problème majeur des mécanismes de relogement : le stockage d'une unique bitstream de configuration pour réduire les besoins de la mémoire et pour accroître la réutilisable des modules matériels générés. Une technique de partitionnement de la région reconfigurable est appliquée dans la méthodologie de relogement proposée pour augmenter l'efficacité d'utilisation des ressources matérielles dans le cas des tâches reconfigurables de tailles variables. Cette méthodologie prend en compte aussi la communication entre différentes régions reconfigurables et la région statique. Pour valider la méthode, plusieurs études de cas sont implémentées. Cette validation montre une utilisation efficace des ressources matérielles ainsi une réduction importante du temps de reconfiguration. La deuxième partie de cette thèse présente et détaille une formulation mathématique afin d'automatiser le floorplanning des zones reconfigurables dans les FPGAs. Les algorithmes de recherche présentés dans cette thèse sont basés sur la technique d'optimisation PLMNE (programmation linéaire mixte en nombres entiers). Ces algorithmes permettent de définir automatiquement l'emplacement, la taille et la forme de la zone reconfigurable dynamique. Nous nous intéressons principalement dans cette recherche à la satisfaction des contraintes de placement des zones reconfigurables et celles liées à la relocation. De plus, nous considérons l’optimisation des ressources matérielles dans le FPGA en tenant compte des tâches de tailles variables. Finalement, une évaluation de l'approche proposée est présentée / Adaptive systems based on Field-Programmable Gate Arrays (FPGA) architectures can benefit greatly from the high degree of flexibility offered by dynamic partial reconfiguration (DPR). Thanks to DPR, hardware tasks composing an adaptive system can be allocated and relocated on demand or depending on the dynamically changing environment. Existing design flows and commercial tools have evolved to meet the requirements of reconfigurables architectures, but that are limited in functionality. These tools do not allow an efficient placement and relocation of variable-sized hardware tasks. The main objective of this thesis is to propose a new methodology and a new approaches to facilitate to the designers the design phase of an adaptive and reconfigurable system and to make it operational, valid, optimized and adapted to dynamic changes in the environment. The first contribution of this thesis deals with the issues of relocation of variable-sized hardware tasks. A design methodology is proposed to address a major problem of relocation mechanisms: storing a single configuration bitstream to reduce memory requirements and increasing the reusability of generating hardware modules. A reconfigurable region partitioning technique is applied in this proposed relocation methodology to increase the efficiency of use of hardware resources in the case of reconfigurable tasks of variable sizes. This methodology also takes into account communication between different reconfigurable regions and the static region. To validate the design method, several cases studies are implemented. This validation shows an efficient use of hardware resources and a significant reduction in reconfiguration time. The second part of this thesis presents and details a mathematical formulations in order to automate the floorplanning of the reconfigurable regions in the FPGAs. The algorithms presented in this thesis are based on the optimization technique MILP (mixed integer linear programming). These algorithms allow to define automatically the location, the size and the shape of the dynamic reconfigurable region. We are mainly interested in this research to satisfy the constraints of placement of the reconfigurable zones and those related to the relocation. In addition, we consider the optimization of the hardware resources in the FPGA taking into account the tasks of variable sizes. Finally, an evaluation of the proposed approach is presented
|
86 |
Integração de veículos elétricos no planejamento da expansão dos sistemas de distribuição /Bañol Arias, Maria Nataly. January 2019 (has links)
Orientador: John Fredy Franco Baquero / Resumo: A crescente penetração dos Veículos Elétricos (VEs) no setor de transportes representa um novo e grande desafio para o planejamento da expansão e da operação dos Sistemas de Distribuição de Energia Elétrica (SDEEs) devido ao correspondente aumento da demanda associada ao carregamento das baterias. Portanto, devem ser desenvolvidos métodos que ajudem os SDEEs a lidar com esses desafios, considerando as incertezas associadas às demandas convencionais e aos VEs. Nesta tese é proposto um método robusto baseado em um modelo de Programação Linear Inteira-Mista (PLIM) para auxiliar a integração de VEs no SDEE. O método proposto permite resolver o problema de planejamento multi-estágio da expansão do SDEE considerando a alocação e o dimensionamento de Estações de Carregamento de VEs (ECVEs). Restrições probabilísticas são usadas na formulação proposta para lidar com as incertezas associadas à demanda, garantindo o cumprimento da capacidade de potência das subestações com um nível de confiança especificado. O modelo proposto para o planejamento da expansão avalia a construção e/ou reforço de subestações, ECVEs e circuitos, assim como também a alocação de unidades de geração distribuída e bancos de capacitores ao longo do horizonte de planejamento. O modelo de PLIM proposto é resolvido através de técnicas de otimização clássica visando garantir a solução ótima do problema. A eficiência e robustez do modelo são verificadas usando sistemas teste de 18 e 54 nós, junto com simulações de Mo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The increasing penetration of electric vehicles (EVs) in the transportation sector represents a new challenge for the expansion planning of electrical distribution systems (EDS) due to the corresponding increase of the energy demand. Therefore, methods to support the EDS considering the uncertainties associated with conventional and EV demands should be developed. This thesis presents a methodology to consider the EV integration into the EDS. A mixed-integer linear programming (MILP) model is proposed to solve the multi-stage expansion planning of EDS considering the allocation and sizing of EV charging stations (EVCSs). Chance constraints are used in the formulation to deal with the uncertainties associated with the demands, guaranteeing the fulfilment of the substation capacities within a given confidence level. The proposed model for the expansion planning considers the construction/reinforce of substations, EVCSs and circuits as well as the allocation of distributed generation units and capacitor banks along the planning horizon. The proposed MILP model guarantees optimality using classical optimization techniques. The efficiency and robustness of the model is verified using two test systems with 18-nodes and 54-nodes. Monte Carlo simulations were carried out to verify the compliance of the proposed chance constraint. / Doutor
|
87 |
Mathematical optimization of unbalanced networks operation with smart grid devices /Sabillón Antúnez, Carlos Francisco. January 2018 (has links)
Orientador: Marcos Julio Rider Flores / Abstract: Electric distribution networks should be prepared to provide an economic and reliable service to all customers, as well as to integrate technologies related to distributed generation, energy storage, and plug-in electric vehicles. A proper representation of the electric distribution network operation, taking into account smart grid technologies, is key to accomplish these goals. This work presents mathematical formulations for the steady-state operation of electric distribution networks, which consider the unbalance of three-phase grids. Mathematical models of the operation of smart grid-related devices present in electric distribution networks are developed (e.g., volt-var control devices, energy storage systems, and plug-in electric vehicles). Furthermore, features related to the voltage dependency of loads, distributed generation, and voltage and thermal limits are also included. These formulations constitute a mathematical framework for optimization analysis of the electric distribution network operation, which could assist planners in decision-making processes. Different objectives related to technical and/or economic aspects can be pursued within the framework; in addition, the extension to multi-period and multi-scenario optimization is discussed. The presented models are built based on mixed integer linear programming formulations, avoiding the use of conventional mixed integer nonlinear formulations. The application of the presented framework is illustrated throughou... (Complete abstract click electronic access below) / Resumo: As redes de distribuição de energia elétrica devem estar preparadas para fornecer um serviço econômico e confiável a todos os clientes, bem como para integrar tecnologias relacionadas à geração distribuída, armazenamento de energia e veículos elétricos. Uma representação adequada da operação das redes de distribuição, considerando as tecnologias de redes inteligentes, é fundamental para atingir esses objetivos. Este trabalho apresenta formulações matemáticas para a operação em regime permanente das redes de distribuição, que consideram o desequilíbrio de redes trifásicas. Modelos matemáticos da operação de dispositivos relacionados à redes inteligentes presentes em redes de distribuição são desenvolvidos (e.g., dispositivos de controle volt-var, sistemas de armazenamento de energia e veículos elétricos). Além disso, características relacionadas à dependência da tensão das cargas, geração distribuída e limites térmico e de tensão também estão incluídos. Essas formulações constituem um marco matemático para a análise de otimização da operação das redes de distribuição de energia elétrica, o que possibilita modelar os processos de tomada de decisões. Objetivos diferentes relacionados a aspectos técnicos e/ou econômicos podem ser almejados dentro deste marco; Além disso, a extensão para otimização multi-período e multi-cenário é discutida. Os modelos apresentados são construídos com base em formulações de programação linear inteira mista, evitando o uso de formulações não-lineare... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor
|
88 |
Planning production and supply chain in energy intensive process industriesWaldemarsson, Martin January 2014 (has links)
To make a difference among the energy intensive process industries, this dissertation addresses production planning and supply chain planning problems related to industrial energy management issues. The energy issue is turning more and more important from different angles, involving price as well as environmental problems due to climate change leading to political pressure on all energy users. The process industry sector is one of the largest users of energy, and thus important to analyse. Process industries are also capital intensive and operate on large and expensive process equipment, making it imperative to plan their production well in order to reach preferable capacity utilisation. Therefore this dissertation strives to locate the most important energy management issues for the long term profitability of process industries, and investigates the symbiotic effects of including energy issues in production and supply chain planning. Three different studies at three case companies are carried out, analysed, and presented in five papers. The cases represent the process industry sectors: chemicals, pulp, and steel. Both qualitative case study methodologies as well as quantitative mathematical modelling and optimisation approaches have been practiced. The research questions are analysed from both an energy system and from a production process point of view, separately as well as combined. Energy is somewhat considered to be the main workforce for process industries and this dissertation exemplifies some of its most important dimensions in this context. Several prerequisites for putting energy management on the strategic agenda are located in a specialty chemical industry where the importance of introducing a strategic perspective on energy, the way energy is used, and the possibilities of increasing alternative revenue from utilising by- and/or co-products differently are pinpointed. Approaches for including energy issues in planning processes are also suggested in terms of a MILP model for the entire supply chain of a pulp company, including decisions on purchase and transportation of raw maerials, production allocation, energy mix, and distribution. Another example is presented based on the perspectives of economics of scale and lot sizing through economic order quantity principles in a steel company. By using real company data, energy smart approaches in planning and scheduling are developed with respect to the most important intersections between the production processes and their supporting energy system. The accumulated resource intensity and embedded energy could, and probably should, hence be more fairly reflected in the product price. The research finally shows some possible impact with including energy issues in a production and supply chain planning model. By planning differently, production prioritisations can be done, and it is not only possible without any large investments, but also prosperous with savings on both energy and money within reach. To conclude, planning of production and supply chain has either a direct or an indirect impact on the energy cost-effectiveness of a company. This dissertation argues that such impact also exists in its mutual form, and is very important when the energy issues are large enough, as they often are in the energy intensive process industry sector. Decision makers should thus beware of the short end of the stick that might be devastating in the long run, but also aware of all the possibilities that can bring success and prosperity when the future begins.
|
89 |
[en] MARITIME INVENTORY ROUTING: A PRACTICAL ASSESSMENT AND ROBUST OPTIMIZATION APPROACH / [pt] ROTEAMENTO DE NAVIOS COM GESTÃO DE ESTOQUES: UMA AVALIAÇÃO PRÁTICA E UMA ABORDAGEM ROBUSTAGUSTAVO SOUTO DOS SANTOS DIZ 11 February 2019 (has links)
[pt] O problema de roteamento de navios com gestão de estoques (conhecido pelo termo em inglês Maritime inventory routing ou MIR) representa um problema prático de logística onde o transportador da carga também é responsável pela manutenção dos estoques do produto transportado nos portos de carga e descarga. Esta tese estuda um caso real do problema MIR. Um conjunto de testes é apresentado de modo a comparar diferentes formulações matemáticas da literatura, a fim de encontrar aquela mais aderente ao problema real. Em função da complexidade computacional do problema, é apresentada uma abordagem heurística que consegue encontrar soluções similares e reduz consideravelmente o tempo computacional quando comparadas com as formulações baseadas em PLIM. No entanto, problemas reais são muito influenciados por aspectos incertos. Sendo assim, é apresentada uma abordagem robusta para a otimização do problema MIR, que considera incerteza no tempo de estadia do navio nos portos. A abordagem apresentada produz soluções para diferentes níveis de robustez. Em outras palavras, considera o risco de variação no tempo de estadia do navio em um porto durante uma operação de carga ou descarga. Assim, é capaz de determinar a probabilidade de inviabilidade da solução encontrada para cada nível de robustez oferecido, além do impacto no custo de transporte à medida que soluções mais robustas são apresentadas. Esta abordagem oferece ao tomador de decisão a medida do trade-off entre robustez e custo de transporte. Desta forma, o mesmo pode determinar qual o nível de conservadorismo irá adotar em sua programação de navios e quanto isto irá impactar o custo de transporte. Os experimentos apresentados identificaram que, aumentos sutís no nível de robustez (com pequeno impacto no custo de transporte) podem reduzir consideravelmente a probabilidade de inviabilidade de uma solução. / [en] Maritime inventory routing (MIR) problem is an academic name for a practical logistic problem that represents the routing or scheduling of vessels to carry product(s) between ports. Meanwhile, the product(s) inventory levels in these ports must remain between operational bounds during the entire planning horizon. This thesis focus on how to support decision on a real-life MIR problem faced by a Brazilian petroleum company. To do so, we structure a set of tests to compare different formulation from literature and identify which is more adherent to real problem. Due to computational complexity of the problem, we present an heuristic approach that provides reasonably good solutions when compared to deterministic mixed integer linear programming (MILP) formulations and reduces considerably the computational time of solving real-life instances. However, uncertainty events have great impact in the ship scheduling planning. Therefore, we propose a robust optimization approach that considers uncertainty in the time spent at ports in each ship visit. Our approach is able to determine the probability of infeasibility and the impact in the objective function for each level of robustness, helping to measure the uncertain aversion of the decision maker. Our experiments identified that, for a certain instance, varying the level of robustness one may reduce the probability of infeasibility from 87 per cent (of deterministic solution) to 2 per cent and it represents an increase in the transportation costs of about 13 per cent.
|
90 |
Méthodes de modélisation et d'optimisation par recherche à voisinages variables pour le problème de collecte et de livraison avec transbordement / Modeling method and optimization by the variable neighborhood search for the pickup and delivery problem with transshipmentTchapnga Takoudjou, Rodrigue 12 June 2014 (has links)
La présente thèse se déroule dans le cadre du projet ANR PRODIGE et est axée sur la recherche de stratégies permettant l’optimisation du transport en général et du transport routier de marchandises en particulier. Le problème de transport support de cette étude est le problème de collecte et livraison avec transbordement. Ce problème généralise plusieurs problèmes de transports classiques. Le transbordement y est utilisé comme levier de flexibilité et d’optimisation. Pour analyser et résoudre ce problème, les analyses sont effectuées suivant trois axes : le premier axe concerne l’élaboration d’un modèle analytique plus précisément d’un modèle mathématique en variables mixtes. Ce modèle permet de fournir dessolutions optimales au décisionnaire du transport mais présente l’inconvénient de nécessiter un temps de résolution qui croit exponentiellement avec la taille du problème. Cette limitation est levée par le deuxième axe d’étude qui permet de résoudre le problème de transport étudié par une méthode d’optimisation approchée tout en garantissant des solutions satisfaisantes.La méthode utilisée est une métaheuristique inspirée de la recherche à voisinages variables (VNS). Dans le troisième axe, l’ensemble des résultats obtenus dans la thèse sont testés en situation de transports réels via le projet PRODIGE. / The thesis is conducted under the ANR project PRODIGE and it is focused on seeking strategies allowing the optimization of transport in general and road freight transport in particular. The transportation problem support for this study is the pickup and delivery problem with transshipment.This problem generalizes several classical transportation problems.Transshipment is used as optimization and flexibility leverage. To study and solve this problem, analyzes are performed along three axes :the first objective concerns the development of an analytical model, more accurately a mathematical model with mixed variables. This model allows providing optimal solution to the decision maker, but has the disadvantage of requiring a time resolution that grows exponentially with the size of the problem. This limitation is overcome by the second line of the study that solves the transportation problem studied by an approximate optimization method while ensuring satisfactory solutions. The method used is a mataheuristic broadly followed the variables neighborhoods research principles. In the third objective, the overall results obtained in the thesis are tested in real transport situation via the PRODIGE project.
|
Page generated in 0.1438 seconds