In-train Forces Research Articles

About the influence of wheel slide protection devices action on longitudinal dynamic of trains

Wheel slide protection devices (WSPD) are destined to avoid important sliding of wheels during braking actions in case of temporarily impaired wheel-rail adhesion by correspondent reductions of air pressure in brake cylinders. Accordingly, longer braking distances and higher longitudinal in-train forces occur, potentially affecting the traffic safety and the passengers comfort. A general analyse and evaluation of these effects are the main targets of the present study. The theoretical considerations are sustained by simulations of braking process, considering situations of normal, respectively diminished wheel-rail adhesion determining random actuations of WSPD. The air pressure evolution in brake cylinders of was experimentally determined on a computerized brake system test stand and adequately used as input in simulations. The results indicate an increase of in-train forces and a more complex evolution of the longitudinal dynamic actions between the vehicles in the case of degraded wheel-rail adhesion, when the random actuation of WSPD have major influence in the whole braking process.

Kriging models for payload distribution optimisation of freight trains

This paper deals with Kriging models applied to optimise braking performances for freight trains. More precisely, it is focused on mass distribution optimisation aimed at reducing the effects of in-train forces among vehicles, e.g. compression and tensile forces, in-train emergency braking. To this end, Kriging models are applied with covariance structure based on the Matérn function, introducing specific input parameters to better outline the payload distribution on the train, also evaluating the shape of the payload distribution. The different shapes, related to the payload distributions, have been implemented into a model through a Python routine, which has been used to ‘assemble’ the simulated trains. The analysed train carries 80% of its maximum payload capacity during an emergency braking from the speed of 30 km/h. Satisfactory results have been obtained considering compression forces, tensile forces and their sum, also considering residuals and diagnositc measures.

Braking induced impact for train to train rescue

ABSTRACTTrain to train rescue means that a disabled train without power supply is rescued by another train. However, the in-train stability problem caused by braking has significant effect on the longitudinal train dynamics. In this paper, the field test for a set of coupled assisting and disabled trains is firstly presented. It is indicated the instability in train or coupler jackknifing phenomenon only occurs under compressed in-train forces. The dynamic models of the rescue train as well as the coupler and draft gear system are then established. The calculated in-train forces and draft gear deflection are compared with that from measured results. The occurring mechanism and subsequent effect of the coupler pitch motion of train to train rescue on tangent tracks are discussed. The coupler yaw motion of the coupled train on curved tracks is also discussed. The braking induced coupler forces if combined with rotational motions can adversely affect the train dynamic performance. An efficient manner to deal with issue is to decrease the braking induced in-train forces by proper train configurations or braking levels. Another approach is to limit the carbody and coupler rotational angles by decreasing secondary clearance of the air spring.

Neuro-adaptive fault-tolerant control of high speed trains under traction-braking failures using self-structuring neural networks

This paper develops an adaptive control scheme for position and velocity tracking control of high speed trains under uncertain system nonlinearities and actuator failures. Neural networks with self-structuring capabilities are integrated into control design, where the number of the neurons can be adjusted online automatically, so that not only the problem inherent in the NN with fixed structure is avoided, but also the negative impacts arising from nonlinear in-train forces, traction/braking uncertain dynamics as well as the unknown actuation faults are effectively attenuated. It is shown that the resultant control algorithms are able to achieve high precision train speed and position tracking under varying operation railway conditions, as validated by theoretical analysis and numerical simulations.

Investigation of in-train stability and safety assessment for railway vehicles during braking

In-train stability of railway vehicles has becoming a major concern for railway vehicles, which refers to the jackknifing behavior of couplers under large in-train forces. For the train to train rescue scenario, braking induced impacts from couplers can adversely affect the dynamic performance of the coupled train. It is indicated from field tests that in-train forces if combined with large rotational angles of couplers can produce vertical components, which will further lead to the interference of adjacent carbodies and structural damages. In this paper, the dynamic model of the train and coupler system is developed. The model verifications are conducted by comparing the calculated responses with the tested results. The safety indices are formulated on the basis of which the running safety of the coupled train is evaluated. The propelling test in the laboratory is conducted to reproduce the coupler jackknifing behavior. The quasi-static analysis and anti-jackknifing mechanism under compressing in-train forces are analysed. Parametric studies are then conducted to propose some limitations for the application of train to train rescue. It is indicated from numerical and testing results that the decrease of the braking deceleration or a limitation of the free rotational angle of couplers is beneficial to lower the amplitude of braking induced impacts.

Simulation of longitudinal dynamics of a freight train operating through a car dumper

ABSTRACTA heavy haul train and car dumper model was created to analyse train longitudinal dynamics during dumping. Influence of such factors as performance curve of draft gears, total free slack in couplers, operating mode of train positioner and braking of last two cars of train on the in-train forces was considered.

Effects of Slow-Acting Brakes Application Time Regulated Limits on Freight In-Train Forces

The paper originally investigates the influence of the admitted ranges of slow-acting filling time of brake cylinder on longitudinal dynamics of freight trains, using experimental air pressure data obtained in tests on filling characteristics. Mechanical and pneumatic models are summarized and numerical simulations were performed for a train composed of six wagon train, in different filling characteristics configurations. The results reflect significant effects on in-train forces values, while evolution and disposition of compression and tensile forces between neighbored vehicles in the long of the train are also affected.

How can trains operate more energy-efficiently?

Faced with rising energy costs, fleet owners are increasingly turning to the Leader driver advisory system (iCOM Assist) to improve the overall efficiency of rail vehicle operations. The system uses route, train and timetable data to calculate the best options to save energy, and provides the train driver with relevant recommendations. These can result in fuel savings of more than 10 %, as well as reduced wear and tear from in-train forces. Leading European freight operator DB Schenker Rail AG is currently installing Leader systems in 300 of its locomotives.

Stabilizing mechanism and running behavior of couplers on heavy haul trains

Published studies in regard to coupler systems have been mainly focused on the manufacturing process or coupler strength issues. With the ever increasing of tonnage and length of heavy haul trains, lateral in-train forces generated by longitudinal in-train forces and coupler rotations have become a more and more significant safety issue for heavy haul train operations. Derailments caused by excessive lateral in-train forces are frequently reported. This article studies two typical coupler systems used on heavy haul locomotives. Their structures and stabilizing mechanism are analyzed before the corresponding models are developed. Coupler systems models are featured by two distinct stabilizing mechanism models and draft gear models with hysteresis considered. A model set which consists of four locomotives and three coupler systems is developed to study the rotational behavior of different coupler systems and their implications for locomotive dynamics. Simulated results indicate that when the locomotives are equipped with the type B coupler system, locomotives can meet the dynamics standard on tangent tracks; while the dynamics performance on curved tracks is very poor. The maximum longitudinal in-train force for locomotives equipped with the type B coupler system is 2000 kN. Simulations revealed a distinct trend for the type A coupler system. Locomotive dynamics are poorer for the type A case when locomotives are running on tangent tracks, while the dynamics are better for the type A case when locomotives are running on curved tracks. Theoretical studies and simulations carried out in this article suggest that a combination of the two types of stabilizing mechanism can result in a good design which can significantly decrease the relevant derailments.

A review of dynamics modelling of friction draft gear

Longer and heavier trains mean larger in-train forces and more complicated force patterns. Practical experience indicates that the development of fatigue failure of coupling systems in long heavy trains may differ from conventional understanding. The friction-type draft gears are the most widely used draft gears. The ever developing heavy haul transport environment requires further or new understanding of friction draft gear behaviour and its implications for train dynamics as well as fatigue damage of rolling stock. However, modelling of friction draft gears is a highly nonlinear question. Especially the poor predictability, repeatability and the discontinuity of friction make this task more challenging. This article reviews current techniques in dynamics modelling of friction draft gears to provide a starting point that can be used to improve existing or develop new models to achieve more accurate force amplitude and pattern predictions.

High-speed train control based on multiple-model adaptive control with second-level adaptation

Speed uplift has become the leading trend for the development of current railway traffic. Ideally, under the high-speed transportation infrastructure, trains run at specified positions with designated speeds at appointed times. In view of the faster adaptation ability of multiple-model adaptive control with second-level adaptation (MMAC-SLA), we propose one type of MMAC-SLA for a class of nonlinear systems such as cascaded vehicles. By using an input decomposition technique, the corresponding stability proof is solved for the proposed MMAC-SLA, which synthesises the control signals from the weighted multiple models. The control strategy is utilised to challenge the position and speed tracking of high-speed trains with uncertain parameters. The simulation results demonstrate that the proposed MMAC-SLA can achieve small tracking errors with moderate in-train forces incurred under the control of flattening input signals with practical enforceability. This study also provides a new idea for the control of in-train forces by tracking the positions and speeds of cars while considering power constraints.

Braking-Penalized Receding Horizon Control of Heavy-Haul Trains

Incorporated with a receding horizon control (RHC) approach, a penalty method is proposed for reducing the energy wasted by braking in the operation of a heavy-haul train. The practical nonlinear model of the train is linearized to design the RHC controller. This controller is then applied to the practical nonlinear dynamics of the train, and its performances are analyzed. In particular, the main focus of this paper is on the impact of the brake penalty on the train's performances. Meanwhile, a fence method is presented to tackle two issues. The first issue is that all the cars in a train cannot be individually controlled due to a limit on the available transmission channels for control systems in a long train. The other issue is that the RHC approach suffers from heavy computation and memory load. Simulations verified that the brake penalty presented in the design can remarkably reduce the energy consumption and in-train forces of a train without sacrificing the velocity tracking performance of the train. Simulations also verified that the fence method is essential to reducing the related computation load when the RHC approach is applied to a long heavy-haul train. Further, it is demonstrated that the fence method can effectively shorten computation time and reduce memory usage without severely jeopardizing the performance of a train.

About Longitudinal Dynamics of Classical Passenger Trains during Braking Actions

There are presented and analyzed specific aspects regarding the main mechanic and pneumatic issues determining the in-train dynamic forces developed during braking actions. Particularities in case of passenger trains are highlighted, with the aim of proving that even in the case of short trains, fitted with UIC type P braking system, longitudinal dynamics can cause significant reactions whose effect cannot be neglected, both in terms of traffic safety and comfort. Numerical examples presented stand for this.

Analysis of the rotation angle of a coupler used on heavy haul locomotives

Increases in train length and axle loads have significantly increased in-train forces for heavy haul trains. These forces when combined with the rotation behavior of the coupler can exert an adverse effect on the operational safety of trains. This paper analyzes the rotation behavior of a coupler resulting from the application of a compressive force. A suitable free-rotation angle for the coupler and a stabilization mechanism are also presented. Simulations were performed using a dynamic model of a train consisting of three heavy haul locomotives and two couplers. The obtained results indicate that trains with free-rotation angles of the coupler of 6°have a better dynamic safety and lower levels of wheel tread wear than trains with an initial free-rotation angle of 8°. Variation of the locomotive’s structural parameters, including the secondary stop free clearance, the distance between front and rear stops and the distance between secondary stop and coupler pin, affects the maximum rotation angle of the coupler and, in turn, the operational safety of the train. The matching of the locomotive’s structural parameters and the free-rotation angle of the coupler should be considered when selecting a heavy haul coupler and buffer system so as to avoid safety problems caused by excessive rotation behavior of the coupler.

Decentralized control of heavy-haul trains with input constraints and communication delays

The heavy-haul trains consist of a large number of locomotives and wagons which usually cover a very long range of train tracks with different slopes and curvatures. As a consequence, the control design for the heavy-haul trains has posed a significant challenge due to the modeling complexity and the complicated traveling conditions, under which the problems of communication delays and input constraints naturally arise. In this paper, a novel decentralized control design is proposed for the heavy-haul trains by explicitly addressing the issues of input constraints and time-varying communication delays. Specifically, the complicated longitudinal dynamical model of the heavy-haul trains is first converted into a double integrator form by introducing a set of state and input transformations. Then, a decentralized cooperative control is proposed to regulate the speeds of individual train units (locomotives and wagons) to the desired profile with the objective of maintaining the minimum in-train force for safety consideration. It is rigorously proved that the closed-loop system is uniformly asymptotically cooperative stable under the least communication conditions among individual train units. Extensive simulations are conducted to validate the performance of the proposed new design.

Data-Based Fault-Tolerant Control of High-Speed Trains With Traction/Braking Notch Nonlinearities and Actuator Failures

This paper investigates the position and velocity tracking control problem of high-speed trains with multiple vehicles connected through couplers. A dynamic model reflecting nonlinear and elastic impacts between adjacent vehicles as well as traction/braking nonlinearities and actuation faults is derived. Neuroadaptive fault-tolerant control algorithms are developed to account for various factors such as input nonlinearities, actuator failures, and uncertain impacts of in-train forces in the system simultaneously. The resultant control scheme is essentially independent of system model and is primarily data-driven because with the appropriate input-output data, the proposed control algorithms are capable of automatically generating the intermediate control parameters, neuro-weights, and the compensation signals, literally producing the traction/braking force based upon input and response data only--the whole process does not require precise information on system model or system parameter, nor human intervention. The effectiveness of the proposed approach is also confirmed through numerical simulations.

Optimal Scheduling and Control of Heavy Haul Trains Equipped With Electronically Controlled Pneumatic Braking Systems

This brief compares the performances of different operation strategies based on optimal scheduling and heuristic scheduling for heavy haul trains equipped with electronically controlled pneumatic braking systems. Train scheduling here refers to an open-loop control design that brings the train to a desired (steady-state) motion trajectory. A (closed-loop) cruise control is used to maintain a steady-state motion of a train. In train handling, energy consumption, speed tracking, and in-train force are concerns for transportation corporations. The last is particularly important for safe train running. An optimal train scheduling as well as an optimal cruise control can take these factors into consideration. A speed profile is assumed first. The objective of the study is to find optimal driving methodologies for an implementation of a desired speed profile with energy consumption and in-train forces considered. Simulation results show that optimal scheduling can improve the performance of the closed-loop controller, and that the 2-2 strategy, the electronically controlled pneumatic/independent distributed power mode, is the best of all strategies.

Idealized steering for hauling locomotives

Most of the passive and active steering developments of traction bogies have been directed towards high speed rail or light rail and commuter rail applications. Previous studies ignored coupler forces and often assumed the wheel rail profiles have ample conicity for the curving task. There is little work directed towards high adhesion rates which is a critical area for freight locomotive performance. In heavy haul train operations ruling grades are often associated with tight curvatures, and steering tasks of hauling locomotives are affected by lateral components of longitudinal train forces. Haul locomotives also have a significant yaw moment from coupler forces making uneven longitudinal creeps useful in balancing these yaw forces. The use of larger diameter wheels on locomotives reduces effective steering conicity such that contact profiles may become insufficient to negotiate tight curves. The large diameter wheels make longitudinal creepage or slip inevitable and Goodall et al. [1] definition of perfect steering unattainable. A new criteria for ideal steering in these conditions is proposed. For hauling locomotives, ideal steering is defined as when the lateral rail creep and contact loads of each axle in one bogie are equal and longitudinal creeps are positive to the applied traction. This definition is applicable to all curving tasks that a hauling locomotive encounters while still applying low wheel rail creep forces. In most of the cases ideal steering can be achieved with zero lateral creep forces. The paper describes equations for quasi-static curving forces including traction and in-train forces. An analysis of curving forces for locomotives with three axle bogies is made with the equations for various curvatures and with haulage locomotives in different train configurations including pusher configuration.

Optimal cruise control of heavy-haul trains equipped with electronically controlled pneumatic brake systems

A closed-loop cruise controller is proposed to minimise the running cost of heavy-haul trains equipped with electronically controlled pneumatic brake systems. Consideration is given to improving velocity tracking, in-train force management and energy usage. To overcome the communication constraints, a fencing concept is introduced, whereby the controller reconfigures adaptively to the current track topology. Simulation results of comparisons between different controllers are provided: open-loop versus closed-loop; velocity tracking versus in-train force. Different train control configurations are also compared: unified control, adaptive fencing and full independent traction and braking.

Modelling and model validation of heavy-haul trains equipped with electronically controlled pneumatic brake systems

In this paper, a longitudinal dynamical model is proposed for heavy-haul trains equipped with electronically controlled pneumatic brake systems. It is validated against experimental data collected on a train with 200 wagons operated by Spoornet on its COALlink. Various data sets from actual trial runs, handwritten and electronic, off-line and on-line, are gathered and reconciled into a validation data set. Most system parameters are set in accordance with the experimental train setup, while certain parameters, such as damping coefficients, are estimated. The model is subjected to recorded input data for particular track sections. The resultant simulation outputs are compared to real-life data. From this study one may conclude that the longitudinal model is a justified choice for considering factors such as speed regulation, in-train force handling and energy consumption management of heavy-haul trains equipped with electronically controlled pneumatic brake systems.