02 Fakultät Bau- und Umweltingenieurwissenschaften

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3

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Institute: search.filters.UBSInstitut.Institut für Eisenbahn- und VerkehrswesenSubject: search.filters.subject.624

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    Hybrid model for proactive dispatching of railway operation under the consideration of random disturbances in dynamic circumstances
    (2017) Zhao, Weiting; Martin, Ullrich (Prof. Dr.-Ing.)
    With the increasing traffic demand and limited infrastructure expansion, railway networks are often operated close to the full capacity, especially in heavily used areas. As a result, the basic timetable is quite susceptible to the operational disturbances, and thereby the propagation and accumulation of delays significantly degrade the service level for customers. To solve this problem, extensive researches have been conducted by focusing on the predefined robust timetables and the real time dispatching algorithm development. However, it has been widely recognized that excessive robust timetables may deteriorate the operating capacity of the railway network and the addition of recovery time and buffer time can be hardly implemented in the congested area. Moreover, most of the conventional dispatching algorithms ignore the further potential random disturbances during the dispatching process, which yield non-implementable dispatching solutions and, as consequences, inferior punctuality and repetitive dispatching actions. To this end, this project aims to develop a new algorithm for real-world dispatching process with the consideration of risk-oriented random disturbances in dynamic circumstances. In the procedure of this project, an operational risk map will be firstly produced: by simulating considerable amount of disturbed timetables with random disturbances generated in a Monte-Carlo scheme and calculating the corresponding expected negative impacts (average total weighted waiting time among all the disturbances scenarios), different levels of operational risk will be assigned to each block section in the studied railway network. Within a rolling time horizon framework, conflicts are detected with the inclusion of risk-oriented random disturbances in each block section, and the near-optimal dispatching solutions are calculated by using Tabu search algorithm. Finally, three indicators including total weighted waiting time, the number of relative reordering and average absolute retiming, are chosen to testify the effectiveness and advantages of the proposed dispatching algorithm. The sensitivity analysis of dispatching-related parameters is conducted afterwards to investigate the most appropriate relevant parameters for the specific studied area. The proposed algorithms are expected to be capable of automatically producing near-optimal and robust dispatching solutions with sufficient punctuality achieved.
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    Approach to determine and evaluate the homogeneity of operating programs in railway operation based on infrastructure occupancy
    (2017) Cao, Nan; Martin, Ullrich (Prof. Dr.-Ing.)
    Contemporary railway traffic requires different train services share the same infrastructure. Capacity consumption together with the homogeneous level of train traffic gives a picture of the efficient use of infrastructure. Previous research suggests that the utilization is more efficient with a homogeneous operating program. During last decades, many researchers tried to describe and/or define the homogeneity of operating programs in rail service; however, no definition considered the infrastructure occupation. In addition, several methods were developed to evaluate the homogeneity in railway operation considering variations in speed, running time and headway. But, the occupancy of infrastructure has not been discussed in the existing methods. An extension of existing definitions is presented from the perspective of the infrastructure, which can be characterized by variations in blocking time, buffer time and running direction. The blocking time, buffer time and running direction describe the occupancy of train path on track sections based on the blocking time model. Accordingly, the homogeneity of operating programs is evaluated through three parameters, namely the homogeneity of blocking time (HBL), the homogeneity of buffer time (HBU) and the homogeneity of running direction (HRD). The overall homogeneity (OH) combined HBL; HBU and HRD to realize an integrity evaluation of homogeneity of operating programs. The results show that this new methodology can quantify the homogeneity of railway operations, not only for track sections but for an entire network, which contributes significantly to the efficient utilization of infrastructure. With the method developed in this thesis, the interrelationship between homogeneity of operating programs and operation quality were investigated quantitatively. Firstly, both the influence of each parameter of homogeneity and the overall homogeneity were analyzed. The operation quality (delay-coefficient) is evaluated for timetables with different train types, arrangements of buffer times and sequences of train runs. The results show that the operation quality deteriorates with less homogeneous timetables, in which the variation in buffer time has a more significant influence. Finally, the influence of homogeneity of operating programs is studied for different traffic flows. The low traffic flow is more sensitive to the homogeneity of buffer time and the homogeneity of blocking time is more significant for high traffic flow.
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    Track data-oriented maintenance intervention limit determination for ballasted light rail tracks through multibody simulations
    (2019) Camacho Alcocer, David; Martin, Ullrich (Prof. Dr.-Ing.)
    Light rail trains (LRT) form an important part of public transport. However, due to the high life-cycle costs, light rail systems are not always considered a suitable solution. One way to reduce life cycle costs is in the area of maintenance management. The maintenance of light rail tracks is based on the experience of the infrastructure managers and focuses on preventive and corrective maintenance. The current track condition is not always sufficiently considered, which means there are hardly any possibilities for optimizing costs. In particular, tolerance and limit values for maintenance measures applicable to light rail systems have not yet been defined or adequately analyzed. Instead, limits are taken from the regular railway guidelines, which means that adequate intervals for maintenance and repair measures are not possible. Tolerances and limits for light rail systems should be based on vehicle reactions, which in turn depends on the current track quality. This would permanently lead to a track condition which allows an operation that is comfortable for the passenger or economically profitable for the infrastructure manager. The focus of this work is on the evaluation of the track geometry of LRT tracks, for which, based on the vehicle reaction, tolerance and limit values for maintenance measures are determined. Since data for sections in very bad condition were not available, artificially poor track conditions are generated by a successive increase of the signal amplitudes within the frequency range of the measured track geometries. The track measurement data is imported into a multi-body simulation software and the vehicle response is calculated on the passage of selected sections for a running time of five minutes. Then the vehicle reaction is evaluated on the basis of the passenger comfort, the track loading and the derailment coefficient, and the quality of the track position is determined. The load on the track body calculated by the multi-body simulation does not exceed permissible limits in comparison to the comfort value and the derailment coefficient. To better illustrate the tolerances and limits for light rail systems derived from the vehicle reaction, a track geometry index is introduced. The Track Geometry Index allows a track manager to visualize the deterioration of the track layout and to divide it into different quality levels. The quality levels help infrastructure managers to determine the time for repair measures in a scheduled manner. Two LRT lines are examined in detail using the method developed here. The result indicates that the routes considered in this work were repaired too early. Future work should detect irregularities in the road through continuously measured accelerations on the vehicle and in the track. In addition, acceleration data can then also be used for the assessment of longer sections of the route using the approach developed here.
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    Modellierung der Wartezeitfunktion bei Leistungsuntersuchungen im Schienenverkehr unter Berücksichtigung der transienten Phase
    (2014) Chu, Zifu; Martin, Ullrich (Prof. Dr.-Ing.)
    Hohe Investitionen beim Ausbau der Eisenbahninfrastruktur und eine begrenzte extensive Erweiterbarkeit des Netzes erzwingen eine Verbesserung der Effizienz des Bahnbetriebs, die gleichzeitig dessen steigende Qualitätsansprüche berücksichtigt. Deswegen ist die Ableitung einer optimalen Auslastung, mit der einerseits die Eisenbahninfrastruktur möglichst stark ausgenutzt wird und andererseits die Betriebsqualität das erwünschte Niveau erreicht, seit langer Zeit Forschungsgegenstand in der Eisenbahnbetriebswissenschaft. Dabei sind die simulative und die analytische Methode zwei übliche Ansätze. In der vorliegenden Arbeit wird die simulative Methode zur Bestimmung der Wartezeitfunktion sowie des optimalen Leistungsbereichs, die von Hertel (1992) entwickelt und von Schmidt (2009) verbessert wurde, weiterentwickelt. Der Schwerpunkt dieser Arbeit liegt auf der realitätsnahen Modellierung des Eisenbahnbetriebs bei der Nutzung der simulativen Methode. Die Beibehaltung des Betriebsprogramms als Randbedingung der Modellbildung wird diskutiert. Darüber hinaus wird durch die explizite Betrachtung der transienten Phase in der Simulation ein entscheidender Effekt, der bei der Modellierung des Eisenbahnbetriebs bislang nicht hinreichend berücksichtigt ist, untersucht. Die Wirkungen der transienten Phase auf die unterschiedlichen Kenngrößen (durchsatzbezogene Leistungsfähigkeit sowie optimaler Leistungsbereich) werden in dieser Arbeit mit einbezogen. Dabei wurden wichtige neue Erkenntnisse gewonnen: - Der neu entwickelte Algorithmus "Dynamisierung der Zeitscheiben mit exakter Zugzahl" kann für die künftige Fahrplanverdichtung bei Leistungsuntersuchungen zielführend genutzt werden. Durch die "Dynamisierung der Zeitscheiben" kann nicht nur eine Zufälligkeit des Fahrplans generiert, sondern auch das als Randbedingung der Untersuchung vorgegebene Betriebsprogramm (Zugmix) beibehalten und somit eine hinreichende Ordnung des Fahrplans gewährleistet werden. - Zur Bestimmung der durchsatzbezogenen Leistungsfähigkeit wurde ein neuer Ansatz entwickelt, mit dem die Wirkungen der transienten Phase in Form eines Zuschlages berücksichtigt werden. Der Zuschlag wird anhand einer neu entwickelten Modellfunktion und der Einflussfaktoren der transienten Phase ermittelt. - Eine neue Modellfunktion der Wartezeitfunktion, die bei der Anpassung der Simulationsergebnisse mathematisch beherrschbar ist und ein höheres (korrigiertes) Bestimmtheitsmaß als die bisher verwendete Modellfunktion besitzt, wurde unter Berücksichtigung der Wirkungen der transienten Phase entworfen. Aus der so bestimmten Wartezeitfunktion gewinnt der optimale Leistungsbereich, der unmittelbar von der Wartezeitfunktion abhängig ist, eine höhere Genauigkeit und Aussagekraft. In der vorliegenden Arbeit, die im Kontext des DFG-Projekts "Direkte experimentelle Bestimmung der maximalen Leistungsfähigkeit bei Leistungsuntersuchungen im spurgeführten Verkehr" entstand ist, wird das Verfahren zur Leistungsuntersuchung nach Hertel (1992) methodisch weiterentwickelt. Die Umsetzung der Erkenntnisse in den gegenwärtig genutzten Werkzeugen zur Leistungsuntersuchung erhöht die Genauigkeit und Aussagekraft der Untersuchungsergebnisse gerade auch in solchen Fällen, bei denen die große Spannweite der Ergebnisse bislang zusätzlich eine aufwendige Interpretation bzw. vertiefte Betrachtungen erforderte.
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    Optimization of schedules with heterogeneous train structure in planning of railway lines
    (2019) Kim, Hyoung June; Martin, Ullrich (Prof. Dr.-Ing.)
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    PULSim: user-based adaptable simulation tool for railway planning and operations
    (2018) Cui, Yong; Martin, Ullrich; Liang, Jiajian
    Simulation methods are widely used in the field of railway planning and operations. Currently, several commercial software tools are available that not only provide functionality for railway simulation but also enable further evaluation and optimisation of thenetwork for scheduling, dispatching, and capacity research. However, the various tools are all lacking with respect to the standards they utilise as well as their published interfaces. For an end-user, the basic mechanism and the assumptions built into a simulation tool are unknown, which means that the true potential of these software tools is limited. One of the most critical issues is the lack of the ability of users to define a sophisticated workflow, integrated in several rounds of simulation with adjustable parameters and settings. This paper develops and describes a user-based, customisable platform. As the preconditions of the platform, the design aspects for modelling the components of a railway system and building the workflow of railway simulation are elaborated in detail. Based on the model and the workflow, an integrated simulation platform with open interfaces is developed. Users and researchers gain the ability to rapidly develop their own algorithms, supported by the tailored simulation process in a flexible manner. The productivity of using simulation tools for further evaluation and optimisation will be significantly improved through the useradaptable open interfaces.
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    3D-printed scale model for detection of railway wheel flats using augmented vibration data from axle box
    (2024) Kim, Eui-Youl; Martin, Ullrich (Prof. Dr.-Ing.)
    As data-driven methods for defect detection become more prevalent in the railway industry, the demand for high-quality data continues to grow. However, field experiments are often time-consuming and constrained by practical limitations. This study introduces a methodology that uses Fused Deposition Modeling (FDM) 3D printing to develop a scale model for simulating wheel flat-induced vibrations, combined with a Long Short-Term Memory (LSTM)-based generative model to produce synthetic vibration data. This approach improves data quality by enhancing quantity, variety, and velocity, while increasing data volume and reducing the need for extensive experimental testing. The LSTM-based model generates realistic synthetic data, minimizing reliance on labor-intensive field experiments and offering a broader spectrum of defect scenarios. By accelerating the data generation process, this method provides an effective alternative in a laboratory setting and contributes to foundational research aimed at improving defect detection and maintenance processes in the railway industry.