It is known that good curving performance and stability often have conflicting requirements given a passive yaw stiffness of the wheelset. Using an active steering system, however, has the potential ...to realize improved curving performance with a satisfactory running stability. Relatively simple active control solutions of yaw relaxation and yaw compensation are illustrated and compared in this paper. In both control solutions, only low-cost electromechanical actuators and load cells are adopted for low-frequency actuations. Associated with a prototype of the two-axle vehicle, the dynamic performances of yaw relaxation and yaw compensation controls for different yaw stiffness configurations are simulated. The homogenous simulation results demonstrate excellent dynamic performance in curve negotiation and stability with the active steering strategies adopted.
This paper presents a model for simulating vehicle–track interaction at high frequencies for investigations of rail roughness growth. The dynamic interaction model developed employs a substructuring ...technique and the whole system consists of a number of substructures that can be modelled independently. The systems are coupled through the forces at the wheel–rail contact and the railpad. A coupled, rotating flexible wheelset, a flexible track model and a non-Hertzian/non-steady contact model have been implemented and results are presented here for a free wheelset on a symmetrical track system with initial random and sinusoidal roughness. Both rigid and flexible wheelsets are considered.
Maintenance and safety inspection of trains is a critical element of providing a safe and reliable train service. Checking for the presence of bolts is an essential part of train inspection, which is ...currently, typically carried out during visual inspections. There is an opportunity to automate bolt inspection using machine vision with edge devices. One particular challenge is the implementation of such inspection mechanisms on edge devices, which necessitates using lighter models to ensure efficiency. Traditional methods have often fallen short of the required object detection performance, thus demonstrating the need for a more advanced approach. To address this challenge, researchers have been exploring the use of deep learning algorithms and computer vision techniques to improve the accuracy and reliability of bolt detection on edge devices. High precision in identifying absent bolts in train components is essential to avoid potential mishaps and system malfunctions. This paper presents “BoltVision”, a comparative analysis of three cutting-edge machine learning models: convolutional neural networks (CNNs), vision transformers (ViTs), and compact convolutional transformers (CCTs). This study illustrates the superior assessment capabilities of these models and discusses their effectiveness in addressing the prevalent issue of edge devices. Results show that BoltVision, utilising a pre-trained ViT base, achieves a remarkable 93% accuracy in classifying missing bolts. These results underscore the potential of BoltVision in tackling specific safety inspection challenges for trains and highlight its effectiveness when deployed on edge devices characterised by constrained computational resources. This attests to the pivotal role of transformer-based architectures in revolutionising predictive maintenance and safety assurance within the rail transportation industry.
The friction coefficient between a railway wheel and rail surface is a crucial factor in maintaining high acceleration and braking performance of railway vehicles; therefore, monitoring this friction ...coefficient is important. Due to the difficulty in directly measuring the friction coefficient, the creep force or creepage, indirect methods using state observers are used more frequently. This paper presents an approach using an unscented kalman filter to estimate the creep force and creepage and the friction coefficient from traction motor behaviours. A scaled roller rig is designed and a series of experiments is carried out to evaluate the estimator performance.
This paper reports on fundamental research to investigate the influence of wheelset flexibility on the development of wheel polygonization of a locomotive. After preparing a flexible wheelset model ...by importing a FE (Finite Element) model into the MBS (Multi-Body System) environment, the investigation work proceeded in 3 steps. Firstly, FRF (Frequency Response Function) of the contact responses against the track irregularity is analysed for a free wheelset and an on-track wheelset, with consideration of rotation effect. Secondly, the influence of the wheelset flexibility on the contact responses excited by white noise is investigated for straight and curved tracks. The final step is to check the influence of the wheelset flexibility on the development of wheel polygonization based on a developed prediction program for railway wheel polygonization. 6 scenarios are investigated with comparison between rigid and flexible wheelsets. Results show that, the wheelset flexibility cannot dominate the railway wheel polygonization in a general sense, unless some prerequisites are fulfilled to provide a suitable environment for the wheelset flexibility to be effectively and continually excited to fluctuate the contact responses, and thereby initiate wheel polygonization. The torsional mode of the wheelset can be effectively excited by stick-slip vibration due to saturated contact adhesion that can occur on track with small curve radii or by large traction torque. In this case, the developed wheel polygonization order will be exactly determined by the wheelset torsional modal frequency and the vehicle speed.
•The influence of wheelset flexibility on wheel polygonal wear is identified based on a prediction program.•All the investigated wheelset flexible modes can be excited to influence the contact responses, but in very different way.•The wheelset flexibility cannot dominate the wheel polygonization unless some prerequisites are fulfilled.•The torsional mode of wheelset can be excited by stick-slip vibration to initiate the wheel polygonization.
This paper presents a comparative study on the applicability of existing popular wear models in simulation of railway wheel polygonization. Four representative wear models developed by BRR (British ...Rail Research), KTH (Royal Institute of Technology), USFD (University of Sheffield), and Professor Zobory respectively, are selected for the comparison with consideration of global and local methods. All the wear models are converted to calculate the instantaneous wear of one contact patch. Uniform expression of the converted wear functions is derived analytically with the equivalent wear coefficient as a useful index to identify the proportional relationship among the wear models quantitatively. Several scenarios grouped by harmonic excitation and random excitation are adopted to assess the fluctuation of the instantaneous wear depth calculated by different wear models. The evolved polygonal wear around the wheel circumference is also compared among the wear models based on a developed prediction program. Simulation results show that all the wear models being investigated in this paper present a similar ability to reflect the fluctuation of the instantaneous wear under various circumstances. Specifically, all wear models can correctly reflect the frequency characteristics of the excitation in a general sense, and the fluctuation phase of the instantaneous wear is obtained with almost the same result among the wear models. There is a very good consistency of trend for all local wear models to simulate the evolved polygonal wear. The mean value and the fluctuation amplitude of the instantaneous wear, as well as the roughness level of the evolved polygonal wear, are all determined by the original wear coefficients used. Besides, the global method is not suitable for calculating the polygonal wear of railway wheels as some sharp points might be generated by the absolute operation for the global WI (Wear Index).
•A uniform expression is analytically derived for four widely used wear models developed by BRR, KTH, USFD, and Professor Zobory respectively.•The derived equivalent wear coefficient is a useful index to identify the quantitative relationship among the wear models.•All of the wear models present a similar ability to reflect the fluctuation of the instantaneous wear depths under various circumstances.•The global method is not suitable for calculation of instantaneous wear depth of railway wheels.
Although a passive independently-rotating wheel-pair (IRW) is not well suited for curve negotiation due to an inability to provide the necessary steering, an active IRW system offers the potential to ...realise perfect curving with a satisfactory running stability. Simple control solutions to realise automatic steering and stability of the IRW system are proposed in this paper. In this control approach, only gyroscopes and tachometers are adopted for the measurements. Associated with a prototype of a two-axle IRW vehicle, the active control strategies for both motor-driven and actuator-driven solutions are illustrated. The simulation results demonstrate significant alleviations in the wheel/rail interactions with perfect-curving performances and superior running stabilities owing to the proposed control strategies.
This paper reports fundamental research on the general conditions for railway wheel polygonal wear to evolve. A common workflow for prediction of railway wheel polygonization is presented including ...assumptions, simulation scheme, and wear models. Based on this workflow, some rules for the evolution of railway wheel polygonization are proposed providing innovative perspectives to understand the basic mechanism of railway wheel polygonization. After summarising these rules, the general conditions for railway wheel polygonal wear to evolve are established. The phase between the instantaneous wear depth and the excitation is the key indicator determining the wheel OOR (Out-Of-Roundness) evolution direction (to grow or to diminish). The evolution tendency curve obtained from the instantaneous wear FRF (Frequency Response Function) is a useful tool to predict the OOR evolution, especially for predicting the OOR order that would grow predominantly at a given speed. If one or more structural modes can dominate the evolution tendency curve, and the energy distribution of track excitation allows this/these structural modes to be excited effectively, corresponding OOR orders can occur dominantly.
This paper outlines the historical development of the wheel and rail profiles currently used on railway vehicles. It also presents the key damage mechanisms involved in wheel-rail contact and ...summarises the methods that have recently been developed by railway engineers to predict the level of wheel and rail damage from these mechanisms. Tools for predicting the key damage modes of wear and rolling contact fatigue (RCF) are explained. Methods of optimising the wheel and rail profiles to reduce the overall damage and therefore improve the efficiency of the railway system are discussed and a case study from the UK of an ‘anti-RCF’ wheel profile is presented. Finally a novel method using a genetic algorithm is discussed which uses a penalty index to optimise the wheel profile for good running, low track forces and rail stress, low wear and RCF.
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