Problème d'affectation des types d'avion aux vols : optimisation robuste et intégration de la demande des passagers

RÉSUMÉ : Le problème d'affectation des types d'avion aux vols (fleet assignment problem, FAP) consiste à déterminer le type d'avion à utiliser pour chaque segment de vol d'un horaire donné de façon à maximiser les profits anticipés, c'est-à-dire les revenus estimés moins les coûts. Les frais d'exploitation dépendent de l'affectation des types d'avion et se calculent relativement bien, tandis que les revenus varient selon la demande des passagers et sont sensiblement plus difficiles à estimer. La plupart des modèles dans la littérature utilisent une estimation par segment de vol, ce qui néglige l'interdépendance des revenus entre les vols ainsi que le débordement et la récupération des passagers. Des modèles de flot de passagers (passenger flow models, PFMs) ont été développés pour améliorer la fonction objectif du FAP, mais ils ont tous divers défauts. La majorité implique un contrôle total de la compagnie aérienne sur ses passagers, sinon ils nécessitent des temps de calcul beaucoup plus importants. De plus, la demande des passagers est sujette à des variations d'une semaine à l'autre au courant d'une saison et d'une journée à l'autre dans une même semaine, ce qui rend sous-optimale toute solution au FAP qui serait répétée période après période sans changement. Cette thèse cherche à accroître la prise en compte de la demande des passagers dans le FAP afin d'améliorer la qualité et la robustesse de la solution. Le premier volet propose un algorithme faisant appel à un modèle de flot de passagers durant la résolution du FAP afin d'améliorer l'estimation des revenus. Dumas (2008) introduit dans sa thèse un modèle de flot de passagers réaliste qui utilise la solution du FAP pour déterminer la répartition des passagers sur les segments de vol et ainsi fournir une meilleure estimation des revenus. Il développe une méthode de résolution itérative qui alterne entre le FAP et le PFM en utilisant cette nouvelle estimation pour mettre à jour les revenus dans la fonction objectif du FAP. Cette méthode donne de meilleurs résultats que la résolution d'un modèle standard, au prix de multiplier les temps de calcul par un facteur de 10 ou plus. L'algorithme que nous proposons utilise le PFM pour réévaluer périodiquement les revenus des segments de vol durant la résolution du FAP par un algorithme heuristique d'énumération implicite. Cette méthode permet d'accélérer les temps de calcul par un facteur de 2 à 3 tout en préservant la qualité de la solution. Le deuxième volet de ce travail de recherche consiste à intégrer la variabilité de la demande dans la modélisation et la résolution du FAP. Lorsque la journée des opérations approche et que la demande se précise, les compagnies aériennes tentent de faire des changements d'affectation pour rentabiliser au maximum leur flotte. Puisque l'affectation initiale n'a pas été faite en tenant compte de ces échanges futurs, il y a généralement peu d'opportunités de réaffectation. Pour remédier à ce problème, nous développons différents modèles d'affectation des types d'avion aux vols avec réaffectation et scénarios de demande. Ces modèles diffèrent selon la complexité du problème de départ et des hypothèses établies. Ils permettent de planifier des opportunités d'échanges de types d'avion en fonction de plusieurs scénarios représentant la variation de la demande au cours d'une saison. Nous développons deux méthodes de résolution que nous testons sur une des variantes du problème. La première méthode utilise la décomposition de Benders pour tenter d'accélérer la résolution, les sous-problèmes étant définis pour les scénarios de demande. Les résultats ne sont pas aussi bons qu'espérés; la convergence de l'algorithme est assez lente et des erreurs numériques se glissent en cours de résolution lorsque les coupes d'optimalité, qui ont des coefficients beaucoup plus élevés que ceux de la matrice de contraintes, sont ajoutées au problème maître. Nous proposons quelques réflexions pour remédier à ces problèmes. La deuxième méthode est une approche directe par CPLEX. Plusieurs expérimentations sont faites sur des instances de tailles diverses avec différents ensembles de scénarios. Les résultats obtenus montrent que l'utilisation de multiples scénarios de demande permet d'améliorer la qualité de la solution de 1 à 3 % comparée au FAP standard et jusqu'à doubler le nombre de réaffectations de types d'avion effectuées en moyenne par rapport à l'utilisation d'un seul scénario représentant la demande moyenne par itinéraire.----------ABSTRACT : The fleet assignment problem (FAP) consists of determining the aircraft type to use on each flight leg of a given schedule in order to maximize the expected profits, which are the expected revenues minus the costs. The operating costs depend on the aircraft type assignment and can be computed relatively easily, while revenues vary with passenger demand and are significantly harder to estimate. Most models in the literature use an estimation per flight leg, that neglects the interdependency of revenues between flights as well as the spill and recapture of passengers. Passenger flow models (PFMs) have been developed to improve the FAP objective function, but they all have various flaws. The majority of them implies total control by the airline company over its passengers, otherwise they require much larger computational times. Furthermore, passenger demand is subject to variations from one week to the other during a season and from day to day in the same week, making sub-optimal any solution to the FAP that would be repeated period after period without change. This thesis seeks to augment the consideration of passenger demand in the FAP in order to improve the quality and robustness of the solution. The first part proposes an algorithm that calls a PFM while solving the FAP to improve the estimated revenues. Dumas (2008) introduced in his thesis a realistic passenger flow model that uses the FAP solution to determine the distribution of passengers on flight legs and thus provides a better estimate of revenues. He developed an iterative solution method that alternates between the FAP and the PFM using this new estimate to update revenues in the FAP objective function. This method gives better results than the usual approach on the standard FAP model, at the cost of increasing computational times by a factor 10 or more. Our proposed algorithm uses the PFM to reevaluate periodically the flight leg revenues while solving the FAP within a heuristic branch-and-bound algorithm. This method speeds up computational times by a factor of 2 to 3 while preserving solution quality. The second part of this research consists of integrating the demand variability in the modeling and solution process of the FAP. When the operation day is approaching and demand becomes more accurate, airlines try to make fleet assignment changes to maximize their fleet utilization. Since the initial fleet assignment was not made taking into account these future exchanges, there is generally few reassignment opportunities. To address this problem, we develop different fleet assignment models with reassignment and demand scenarios. These models differ depending on the initial problem complexity and the assumptions made. They allow to plan aircraft type exchange opportunities based on several scenarios representing demand variation during a season. We develop two solution methods that we test on one of the problem variants. The first method uses Benders decomposition to try to accelerate the solution process, sub-problems being defined for the demand scenarios. The results are not as good as hoped for; the convergence of the algorithm is quite slow and numerical errors are introduced during the solution process when optimality cuts, which have much higher coefficients than those of the constraint matrix, are added to the master problem. We offer some thoughts to remedy to these problems. The second method is a direct approach using CPLEX. Several tests are done using instances of various sizes with different sets of scenarios. The results show that using multiple scenarios improves solution quality by 1 to 3% relative to the standard FAP and up to double the number of aircraft type reassignments done on average compared to using a single scenario representing the average demand per itinerary

Standard concepts for performance improvements in the airport operations areas: global interoprability

Because of the exponential growth of air traffic and its importance of integration of countries, the implementation of improvements in the Global ATM system is becoming increasingly necessary. Within this scope, ICAO brings, within its Global Air Navigation Plan (GANP), an easily understood methodology called: “Aviation System Blocks Upgrade” (ASBU). It defines a language with a programmatic and flexible approach, aiming at performance improvements in the systems. And one of the sectors where one of these performance improvements is sought, as recommended in the ASBU, is the Airport Operations Area. In this area is the Airport Collaborative Decision Making (A-CDM) process. This research aimed to review and improve the A-CDM method to enable its use in airports with lower disbursement capacity. It is based on regulations issued by the International Civil Aviation Organization (ICAO) and academic papers. Theoretically, it went deeper into the various global air navigation systems, such as the processes employed by the European Organization for the Safety of Air Navigation (EUROCONTROL) and the Federal Aviation Administration (FAA). Positions from entities such as the International Air Transport Association (IATA) and the Civil Air Navigation Services Organization (CANSO) were also researched. Subsequently, case studies of airports and interviews with international experts with knowledge on the subject were carried out. Finally, a survey was conducted with members of the Air Sector from around the world. Always focused on seeking compatibilities and opportunities for improvement in the process, mainly in economic gains. According to the sequential strategy exposed above, a scenario analysis is done based on the results obtained at the end of the work. Then, a conclusion is presented, which aims to to apply the referred system, not only in countries with high capacity disbursement but mainly to deliver a solution that allows its application in countries and airports with medium to low financial resources. This solution presented is the goal sought in the research.Tendo em vista o crescimento exponencial do tráfego aéreo e a sua importância na integração dos países, a implantação de melhorias no sistema ATM Global torna-se cada vez mais necessária. Neste sentido a ICAO preconiza, dentro do seu Global Air Navigation Plan (GANP), uma metodologia de fácil entendimento chamada: “Aviation System Blocks Upgrade” (ASBU). Tal metodologia define uma linguagem com abordagem programática, e flexível, visando melhorias de desempenho nos sistemas. E um dos setores onde é procurada uma dessas melhorias de desempenho, conforme preconizado no ASBU, é a área de Operações Aeroportuárias e, em particular, o processo de Airport Colaborative Decision Making (A-CDM). Esta investigação visou realizar uma revisão do método A-CDM, com base em regulamentos e trabalhos acadêmicos sobre o assunto. Aprofundando teoricamente com base nos diversos sistemas de navegação aérea globais, como os processos empregados pela European Organisation for the Safety of Air Navigation (EUROCONTROL) e pela Federal Aviation Administration (FAA). Também foram pesquisados os posicionamentos a respeito do tema de entidades associativas, como da Airports Council International (ACI), da International Air Transport Association (IATA) e da Civil Air Navigation Services Organisation (CANSO). De forma subsequente realizaram-se estudos de caso de aeroportos e foram realizadas entrevistas com especialistas internacionais conhecedores do assunto. Finalmente realizou-se um inquérito com integrantes do Setor Aéreo de todo o mundo. Sempre com o foco de buscar compatibilidades e oportunidades de melhoria no referido processo, principalmente em termos de ganhos econômicos. Ao final do trabalho, de acordo com a estratégia sequencial acima exposta, e com base no resultados colhidos, é feita uma análise de cenário e apresentada uma conclusão, a qual visa que o referido sistema possa ser aplicado, não somente em países de grande capacidade de investimento mas também, e principalmente, apresentar uma solução que permita sua aplicação em países, e aeroportos, com médios a baixos recursos financeiros. Sendo este o resultado buscado na pesquisa

Technology assessment of future intercity passenger transporation systems. Volume 2: Identification of issues affecting intercity transportation

Papers on major issues and trends that affect the future of intercity transportation are presented. Specific areas covered include: political, social, technological, institutional, and economic mechanisms, the workings of which determine how future intercity transporation technologies will evolve and be put into service; the major issues of intercity transportation from the point of view of reform, including candidate transporation technologies; and technical analysis of trends affecting the evolution of intercity transportation technologies

AICPA audit and accounting manual : nonauthoritative technical practice aids, as of June 1, 1994

https://egrove.olemiss.edu/aicpa_guides/1745/thumbnail.jp

AICPA audit and accounting manual : nonauthoritative technical practice aids, as of June 1, 1995

https://egrove.olemiss.edu/aicpa_guides/1755/thumbnail.jp

Federal Register

Daily publication of the U.S. Office of the Federal Register contains rules and regulations, proposed legislation and rule changes, and other notices, including "Presidential proclamations and Executive Orders, Federal agency documents having general applicability and legal effect, documents required to be published by act of Congress, and other Federal agency documents of public interest" (p. ii). Table of Contents starts on page iii

AICPA audit and accounting manual : nonauthoritative technical practice aids, as of June 1, 1996

https://egrove.olemiss.edu/aicpa_guides/1969/thumbnail.jp

Federal Register

Daily publication of the U.S. Office of the Federal Register contains rules and regulations, proposed legislation and rule changes, and other notices, including "Presidential proclamations and Executive Orders, Federal agency documents having general applicability and legal effect, documents required to be published by act of Congress, and other Federal agency documents of public interest" (p. ii). Table of Contents starts on page iii

Suddenly, tomorrow came... A history of the Johnson Space Center

This book chronicles the history of the Johnson Space Center into 17 chapters with a forward written by Donald K. Slayton. Photographs and illustrations are provided. This book becomes part of the NASA history series