1,720,953 research outputs found
Running time supplements: Energy-efficient train control versus robust timetables
No full textEnergy-efficient train operation is not yet included in the timetable design process in the Netherlands. Hence, running time supplements are not optimally distributed in the timetable. Therefore research has been conducted on the possibilities to better incorporate energy-efficient train operation into the railway timetable. This paper describes the developed EZR model (energy-efficient operation or in Dutch ‘EnergieZuinig Rijden’) based on optimal control theory and algorithm that determines the joint optimal cruising speed and coasting point for individual train trips; taking into account a desired robustness, the possibilities for energy-efficient operation, and the desired punctuality during operations. The model is applied on a case study on a sprinter/local train line in the Netherlands between Utrecht Centraal and Rhenen. The model results show that it is better to distribute the running time supplements evenly than concentrating it near the main stations.Transport & PlanningCivil Engineering and Geoscience
Effect of regenerative braking on energy-efficient train control
No full textAn important topic to reduce the energy consumption in railways is the use of energy-efficient train control (EETC). Modern trains allow regen-erative braking where the released kinetic energy can be reused. This regener-ative braking has an effect on the optimal driving regimes compared to trains which can only use mechanical braking. This paper compares the impact of regenerative braking on the optimal train control strategy on level track. The energy-efficient train control problem is modelled as an optimal control problem over distance and solved using a Pseudospectral Method. Three different braking strategies are compared: mechanical braking only, a combination of mechanical and regenerative braking, and regenerative braking only. The result of a case study show that energy savings of at least 28% are possible by including regenerative braking
Energy-efficient Train Timetabling
No full textRailways in Europe need to reduce CO2 emissions and energy usage to contribute to sustainability. One of the measures that railway undertakings can apply with low investment cost and both high reductions in CO2 emission and energy consumption, is energy-efficient train trajectory optimization. Another efficient measure is incorporating energy-efficiency in the timetable design. The aim of this thesis is to incorporate energy-efficient train trajectory optimization in the timetable design in order to improve the potential for energy-efficiency of railways. The thesis develops and applies models for the energy-efficient traincontrol problem for a single train over (multiple) stops with both mechanical and regenerative braking behavior. In addition, energy-efficient train trajectory optimization is incorporated in timetabling by formulating and developing algorithms for a multiple-objective optimization problem applied on a corridor with multiple interacting trains.TRAIL Thesis Series no. T2022/1, the Netherlands TRAIL Research SchoolTransport and Plannin
Rijtijdspeling in treindienstregelingen: Energiezuinig rijden versus robuustheid
No full textCommissioned by the Dutch Railways Operation (NS Reizigers) research has been conducted on the possibilities to better incorporate energy-efficient train operation into the timetable. The motivation for this research is based on the fact that energy-efficient operation is not yet optimally included in the timetable design. This is because of the fact that the running time supplement is not optimally divided. Running time supplement or slack time is the running time above the minimal running time between two timetable points. The objective of the research is to develop a model which determines the optimal coasting point and the optimal cruising speed for trains and the associated running time supplement distribution; taking into account the desired robustness, the possibilities for energy-efficient operation and the desired punctuality during the execution of the timetable. The behavior of a train is described by four driving regimes: acceleration, cruising, coasting and braking. With these driving regimes this study considers two driving strategies: time optimal and energy-efficient. The time optimal driving strategy requires a train to drive as fast as possible from A to B using the driving regimes acceleration, braking and possibly cruising. The energy-efficient driving strategy requires a train to drive also from A to B using as less as possible traction energy given the available time from the timetable. The coasting regime is an important part in this strategy. The energy-efficient driving strategy is determined by the optimal control theory. The algorithm which is applied in MATLAB determines the energy-efficient driving strategy by calculating the optimal coasting point and the optimal cruising speed given the time from the timetable. The model has been applied on the section Utrecht Central – Rhenen for sprinter train series 7400. The results of this research show that there are yearly energy savings possible of almost \u80 26.400 if the energy-efficient driving strategy is used instead of the UZI (‘Universeel Zuinig rijden Idee’) method of NS Reizigers. Moreover the results show that using a uniform distribution of the running time supplements leads to extra energy savings and an improvement for the punctuality compared to the method of tightening the timetable. Tightening the timetable means that the running time supplements are placed as much as possible short before stations where the punctuality is measured. These yearly extra savings which are possible by the uniform distribution instead of the current slack time are almost \u80 44.000 for the energy-efficient driving strategy and are almost \u80 27.500 for the UZI method on the total section.Transport & PlanningTransport & PlanningCivil Engineering and Geoscience
Energy-efficient train control using nonlinear bounded regenerative braking
No full textEnergy-efficient train control (EETC) has been studied a lot over the last decades, because it contributes to cost savings and reduction of CO2 emissions. The aim of EETC is to minimize total traction energy consumption of a train run given the running time in the timetable. Most research is focused to apply mechanical braking on this problem. However, current trains are able to use regenerative braking, which leads to another optimal driving strategy compared to mechanical braking. Research on EETC with a realistic nonlinear bounded model for regenerative braking or a combination between regenerative and mechanical braking is limited. The aim of this paper is to compare the difference between the EETC with regenerative and/or mechanical braking. First, we derive the optimal control structure for the problems with different braking combinations. Second, we apply the pseudospectral method on different scenarios where we investigate the effect of varying speed limits and gradients on the different driving strategies. Results indicate that compared to pure mechanical braking, combined regenerative and mechanical braking leads to a driving strategy with higher energy savings, a lower optimal cruising speed, a shorter coasting phase and a higher speed at the beginning of the braking phase. In addition, a nonlinear bounded regenerative braking curve leads to a different driving strategy compared to a constant braking rate that is commonly used in literature. We show that regenerative braking at a constant braking rate overestimates the total energy savings.Transport and Plannin
Ontwerpmethoden van Dienstregelingen, verkennend onderzoek naar de ontwerpmethodiek per fase in het planningsproces bij NS & ProRail.
No full textGraduation at faculty: Civil Engineering and Geosciences (CITG), Mechanical, Maritime and Materials Engineering (3mE), Technology, Policy and Management (TPM). This thesis deals with real-world plannings problems of timetable design. Improving the timetable design methodology results in a more reliable timetable and a higher quality for passengers. This research first identified the Dutch timetable design process. Afterwards the weaknesses of the Dutch timetable design methodology is identified. These identifications are made by conducting interviews within NS & ProRail. In the third section a case study is conducted. The Dutch 2014 timetable is simulated and compared with a conflict-free timetable which was constructed using microscopic methods (planning in seconds instead of minutes and headways calculated by blocking times instead of plan norms). The simulations resulted in 37% less conflicts and a decrease of 8% delay. Further research is recommended to validate the conclusions in this paper and to investigate the practical usability of a microscopic methodology in an actual design process.Civil Engineering and GeosciencesTransport & PlanningTI
Pseudospectral optimal train control
No full textIn the last decade, pseudospectral methods have become popular for solving optimal control problems. Pseudospectral methods do not need prior knowledge about the optimal control structure and are thus very flexible for problems with complex path constraints, which are common in optimal train control, or train trajectory optimization. Practical optimal train control problems are nonsmooth with discontinuities in the dynamic equations and path constraints corresponding to gradients and speed limits varying along the track. Moreover, optimal train control problems typically include singular solutions with a vanishing Hessian of the associated Hamiltonian. These characteristics make these problems hard to solve and also lead to convergence issues in pseudospectral methods. We propose a computational framework that connects pseudospectral methods with Pontryagin's Maximum Principle allowing flexible computations, verification and validation of the numerical approximations, and improvements of the continuous solution accuracy. We apply the framework to two basic problems in optimal train control: minimum-time train control and energy-efficient train control, and consider cases with short-distance regional trains and long-distance intercity trains for various scenarios including varying gradients, speed limits, and scheduled running time supplements. The framework confirms the flexibility of the pseudospectral method with regards to state, control and mixed algebraic inequality path constraints, and is able to identify conditions that lead to inconsistencies between the necessary optimality conditions and the numerical approximations of the states, costates, and controls. A new approach is proposed to correct the discrete approximations by incorporating implicit equations from the optimality conditions. In particular, the issue of oscillations in the singular solution for energy-efficient driving as computed by the pseudospectral method has been solved.Transport and Plannin
Review of energy-efficient train control and timetabling
No full textThe energy consumption of trains is highly efficient due to the low friction between steel wheels and rails, although the efficiency is also influenced largely by the driving strategy applied and the scheduled running times in the timetable. Optimal energy-efficient driving strategies can reduce operating costs significantly and contribute to a further increase of the sustainability of railway transportation. The railway sector hence shows an increasing interest in efficient algorithms for energy-efficient train control, which could be used in real-time Driver Advisory Systems (DAS) or Automatic Train Operation (ATO) systems. This paper gives an extensive literature review on energy-efficient train control (EETC) and the related topic of energy-efficient train timetabling (EETT), from the first simple models from the 1960s of a train running on a level track to the advanced models and algorithms of the last decade dealing with varying gradients and speed limits, and including regenerative braking. Pontryagin’s Maximum Principle (PMP) has been applied intensively to derive optimal driving regimes that make up the optimal energy-efficient driving strategy of a train under different conditions. Still, the optimal sequence and switching points of the optimal driving regimes are not trivial in general, which led to a wide range of optimization models and algorithms to compute the optimal train trajectories and more recently to use them to optimize timetables with a trade-off between energy efficiency and travel times
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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