Fakulta elektrotechniky a informatiky / Faculty of Electrical Engineering and Informatics
Stálý URI pro tuto komunituhttps://hdl.handle.net/10195/3847
Práce obhájené před rokem 2008 jsou uloženy pouze v kolekci Vysokoškolské kvalifikační práce
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Článekpeer-reviewedpostprint Omezený přístup Automated Construction of Mesoscopic Railway Infrastructure Models Supporting Station Throat Capacity Assessment(2023) Veselý, Petr; Kavička, Antonín; Krýže, PavelAssessment of the traffic capacity of a rail infrastructure involved within railway stations is one of the basic components of the rail transport planning process. An important part of the rail infrastructure in the stations is station throat, which typically comprises many switches and track crossings. Station throat acts as operating bottleneck that frequently has the largest impact on the station’s traffic capacity. The capacity of a station throat is often conveniently assessed based on the use of mesoscopic computer simulation. This requires (among other things) a suitable submodel of the throat infrastructure to be set up. This article presents innovative algorithms for the automated creation of mesoscopic target model of station throat based on consecutive transformations of an initial (intuitive) microscopic model. Compared to the hitherto used manual process, the automated procedure accelerates the construction of the target station throat model and eliminates its structural errors. The applied research method is based both on the original design of the target mathematical model graph (a vertex-weighted directed graph) for the representation of the station throat infrastructure and on the design and verification of innovative graph algorithms that perform multiple aggregation transformations of this model in order to perform its maximum admissible topological simplification. The results of the research conducted have helped to enhance and efficiently use the station throat capacity assessment methodology. The use of the algorithms is demonstrated in a case study concerning station throats within a minor railway station in the Czech Republic.Článekpeer-reviewedpublished Otevřený přístup Reflective Nested Simulations Supporting Optimizations within Sequential Railway Traffic Simulators(ACM (Association for Computing Machinery), 2022) Diviš, Roman; Kavička, AntonínThis article describes and discusses railway-traffic simulators that use reflective nested simulations. Such simulations support optimizations (decision-making) with a focus on the selection of the most suitable solution where selected types of traffic problems are present. This approach allows suspension of the ongoing main simulation at a given moment and, by using supportive nested simulations (working with an appropriate lookahead), assessment of the different acceptable solution variants for the problem encountered-that is, a what-if analysis is carried out. The variant that provides the best predicted operational results (based on a specific criterion) is then selected for continuing the suspended main simulation. The proposed procedures are associated, in particular, with the use of sequential simulators specifically developed for railway traffic simulations. Special attention is paid to parallel computations of replications both of the main simulation and of supportive nested simulations. The concept proposed, applicable to railway trafficmodelling, has the following advantages. First, the solution variants for the existing traffic situation are analyzed with respect to the feasibility of direct monitoring and evaluation of the natural traffic indicators or the appropriate (multi-criterial) function. The indicator values compare the results obtained from the variants being tested. Second, the supporting nested simulations, which potentially use additional hierarchic nesting, can also include future occurrences of random effects (such as train delay), thereby enabling us to realistically assess future traffic in stochastic conditions. The guidelines presented (for exploiting nested simulations within application projects with time constraints) are illustrated on a simulation case study focusing on traffic assessment related to the track infrastructure of a passenger railway station. Nested simulations support decisions linked with dynamic assignments of platform tracks to delayed trains. The use of reflective nested simulations is appropriate particularly in situations in which a reasonable number of admissible variants are to be analyzed within decision-making problem solution. This method is applicable especially to the support of medium-term (tactical) and long-term (strategic) planning. Because of rather high computational and time demands, nested simulations are not recommended for solving shortterm (operative) planning/control problems.Článekpeer-reviewedpublished Otevřený přístup RegioRail-GNSS Train-Positioning System for Automatic Indications of Crisis Traffic Situations on Regional Rail Lines(MDPI, 2022) Fikejz, Jan; Kavička, AntonínThe identification of the position of rail vehicles plays a crucial role in the control of rail traffic. Available, up-to-date information on the position of vehicles allows us to efficiently deal with selected traffic situations where the position of vehicles is very important. The main objective of this article is to introduce (i) a concept of a solution for identification of the current position of rail vehicles based on the worldwide-recognized system of the GNSS with the use of an original railway network data model, and (ii) the use of this concept as supplementary support for the dispatcher control of rail traffic on regional lines. The solution was based on an original, multilayer rail network data model supporting (i) the identification of rail vehicle position and (ii) novel algorithms evaluating the mutual positions of several trains while detecting the selected crisis situation. In addition, original algorithms that enable automatic network model-building (on the database server level) directly from the official railway infrastructure database were developed. The verification of the proposed solutions (using rail traffic simulations) was focused on the evaluation of (i) the changing mutual positions (distances) of trains on the railway network, (ii) the detection of nonstandard or crisis traffic situations, and (iii) the results of the calculations of necessary braking distances of trains for stopping and collision avoidance. The above verification demonstrated the good applicability of the proposed solutions for the potential deployment within supplementary software support for real traffic control. The described concept of the supplementary support determined for railway traffic control (using the localization of trains by means of the GNSS) is intended mainly for regional, single-rail lines. This type of line is very often not sufficiently equipped with standard signaling and interlocking equipment to ensure the necessary traffic safety. Therefore, when deploying this support, the new algorithms for the automatic detection of critical traffic situations represent a significant potential contribution to increasing operational safety.Článekpeer-reviewedpublished Otevřený přístup Dynamic Search of Train Shortest Routes Within Microscopic Traffic Simulators(IEEE (Institute of Electrical and Electronics Engineers), 2022) Kavička, Antonín; Diviš, RomanComputer simulations are frequently used for rail traffic optimization. This approach, referred to as simulation-based optimization, typically employs simulation tools - simulators that are designed to examine railway systems at various levels of detail. Microscopic rail traffic simulators find use when examining rail traffic and the rail infrastructure in great detail. Such simulators typically serve to follow the positions and motions of rail vehicles (trains, locomotives, train cars) and their relocation as well as segments of the rail infrastructure (tracks, switches, track crossings). One of the typical problems to be solved by microscopic simulators within a simulation experiment is to determine the realistic (optimal) train and shunting routes (within the currently occupied infrastructure) along which the rail vehicles are moved. This paper describes novel dynamic route searching algorithms applicable to the relocation of rail vehicles within track infrastructure of railway systems. The following main topics are presented in turn: overview of solutions to the problem of finding track routes in the literature, a suitable rail infrastructure model (associated with algorithms that seek admissible routes for the transfer of the relocation objects of given lengths), graph search algorithms computing the shortest track routes (represented by the admissible shortest walks on graphs), illustrative examples of algorithms' deployment, computational complexity of presented algorithms, comparison with other algorithms and summary of the benefits of newly developed algorithms. The use of the algorithms within the simulation tools (working at the microscopic level of detail) extends the modelling possibilities when searching for realistic track routes (especially for complicated shunting operations), which contributes to better modelling of complex railway traffic (than in the relevant existing rail traffic simulators) and thus to better application of the results of traffic simulations in practice.Článekpeer-reviewedpublished version Otevřený přístup Dynamic Automated Search of Shunting Routes within Mesoscopic Rail-Traffic Simulators(Hindawi limited, 2021) Kavička, Antonín; Krýže, PavelSoftware tools using computer simulations are frequently used in the research and optimization of railway transport systems. Such simulations serve to examine different railway traffic scenarios (which typically reflect different timetables and railway infrastructure configurations). During the simulation experiments, it is necessary, among other things, to solve tasks related to the determination of track routes along which individual trains or parts of train sets are moved. Many simulation tools require the basic and alternative permissible track routes to be manually specified before starting the simulations, which is a relatively tedious and time-consuming process. Classical graph algorithms cannot be applied to solve the problem of automatic calculation of the routes because they are unable to take into account the length of the object being moved or recognise changes in the direction of its movement. This article presents original innovative algorithms focused on automated dynamic search of track routes (applying an appropriate optimization criterion), which is performed during simulation experiments within simulators working at the mesoscopic level of detail. The algorithms are based on a mathematical model (represented by a specifically designed weighted digraph) that appropriately reflects the actual track infrastructure. The dynamic calculation of each specific track route for a train or a group of railway vehicles considers both the total train set length and the current railway infrastructure occupancy, including blocked parts of the infrastructure due to intervention of the interlocking system. In addition, the places where the train set movement direction is changed can be identified on each route found. Applications of the algorithms and of the mathematical model of the track layout are demonstrated on a model track infrastructure.