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This paper presents an in-depth analysis of steering and guidance problems of independently rotating wheels (IRWs) in railway vehicles and provides an engineering insight into the possibilities for passive and/or semi-active control possibilities that do not require expensive full-active systems. The theoretical development is then supported in the study by carrying out a comprehensive performance evaluation in comparison with a full active control. The study demonstrates that the independently rotating wheelset may be effectively controlled via semi-active approaches to provide the wheelsets with the necessary steering on curves and self-centring ability on a straight track with irregularities with performance comparable with full active systems. [ABSTRACT FROM AUTHOR]

Rack railway is a rail transportation that utilizes the gear-rack engagement to supply the traction forces on large-slope lines, primarily employed in mountainous regions where the conventional trains cannot operate due to the wheel-rail adhesion limitations. However, there is limited research on this system dynamics and further analysis is required to understand the interaction mechanism between the rack vehicle and track. Based on the typical vehicle-track coupled dynamics theory, the rack vehicle-track spatially coupled dynamics model is developed in this paper to evaluate the dynamic behaviours of the rack vehicle and the track system running on large-slope line with a detailed modeling of the longitudinal motion for the rack and sleeper, where the time-varying gear-rack mesh stiffness and the rail geometrical irregularity are incorporated. The excellent agreement observed between simulated and field-test results serves as strong validation for developed dynamics model. The results demonstrate that the vibration responses of the wheelset and the rack are dominated by the gear-rack mesh excitations. It should be noticed that the wheel loads are reduced by the presence of the gear-rack engagement. Furthermore, the vibration of the sleeper can explicitly reflect the gear-rack mesh characteristics through the transfer of the rack fastener. [ABSTRACT FROM AUTHOR]

For a set M of vertices and an edge e of a graph G, let $ P_G(M, e) $ P G (M , e) be the set of the pair $ (x, y) $ (x , y) with a vertex x of M and a vertex y of $ V(G) $ V (G) such that $ d_G(x, y)\neq d_{G-e}(x, y) $ d G (x , y) ≠ d G − e (x , y). For a vertex x, let $ EM(x) $ EM (x) be the edge set e such that there exists a vertex v in G with $ (x, v) \in P(\{x\}, e) $ (x , v) ∈ P ({ x } , e). A set M of vertices of a graph G is distance-edge-monitoring set if every edge e of G is monitored by some vertex $ v\in M $ v ∈ M , that is, for any $ e \in E(G) $ e ∈ E (G) , we have $ P_G(M, e)\neq \emptyset $ P G (M , e) ≠ ∅. The distance-edge-monitoring number of a graph G, denoted by $ \operatorname {dem}(G) $ dem ⁡ (G) , is defined as the smallest size of distance-edge-monitoring sets of G. In this paper, we study the distance edge monitoring number of pseudo wheel graphs, that is, some variants of wheel graph. [ABSTRACT FROM AUTHOR]

The identification of Wheel/Rail Force (WRF) based on acceleration is a cheaper and convenient way to ensure safe operation. For this purpose, this paper describes an approach for the estimation of Vertical Wheel/Rail Force (VWRF) using dynamic signals from a track inspection train (TIT). Based on the vehicle dynamics theory, a VWRF estimation model is established, by which VWRF can be estimated with the measured vehicle acceleration. Rolling angle is a non-constant and hard-measured value which will affect estimation results. By deducing its relation with the difference between left and right track profiles, it can be got through the Vertical Axle Box Acceleration (VABA) and the length of the axle box. VWRF cannot be estimated only by filtering the Axle Box Acceleration (ABA). The mass participating in vibration (PVM) also has a great influence on it. With many tests and calculations, the relationship between the PVM and the wheelset mass is concluded, which made the estimation results much more accurate. The proposed method provides the basis for online high-precision estimate WRF and ensures safe operation. By comparing with a commercial WRF Inspection System, the railway application results identified that the proposed method can produce a satisfactory result. [ABSTRACT FROM AUTHOR]

Wheel profile optimisation for variable gauge high-speed trains is required to ensure good vehicle operation performance with two rail gauges, therefore, there is an urgent need to further optimise the wheel profile of variable gauge high-speed trains. This paper proposed the IRSFT-KSM-NSGA-II method to optimise a new wheel profile. Firstly, a new three-parameter improved rotary-scaling fine-tuning (IRSFT) wheel profile generation method was proposed. Then a dynamic model of a variable gauge high-speed train is established, and the clearance between the bushings is considered. The dynamic responses of the vehicle with the generated profiles are calculated and analysed. The wheel profile is optimised using the Kriging surrogate model-Non dominated sorting genetic algorithm-II (KSM-NSGA-II) algorithm. Finally, the dynamic and wear performance of the vehicle before and after the wheel optimisation is verified. The critical speed of the variable gauge high-speed trains is effectively increased, and the ride indexes and safety indexes are improved. When the optimised wheel profile LMB10opt is matched with the rail profile CHN60, the maximum wear depth of the wheel profile is reduced by 11.6%. When the LMB10opt is matched with the P65, the maximum wear depth is reduced by 9.7% and the wear is more uniform. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into high-performance tire characteristics at handling limits. Analysis of the tire characteristics has been conducted using the data obtained from indoor test rigs and vehicle tests. The test rig utilised a flat track test platform to obtain tire forces with precise controllability and measurability. As for the vehicle tests, driving data of a professional driver was obtained for repeatability through a high-performance test vehicle equipped with a wheel force transducer (WFT) at each wheel and a Differential Global Positioning System (DGPS). This study is primarily focused on obtaining a deeper insight into vehicle control through an analysis of tire force characteristics at handling limits. The analysis of indoor test data utilised the Magic Formula to obtain an appropriate model capable of describing real-world tire characteristics. An optimisation-based friction ellipse has been proposed to describe the tire force limits in particular. The solution of the proposed optimisation problem allows for an envelope to be generated that accurately reflects the tire force limits. Additionally, a normalised friction circle model has been proposed to quantify tire friction usage based on the proposed friction ellipse, providing a methodology to monitor the friction use of each wheel. [ABSTRACT FROM AUTHOR]

In this paper, a combined robust fault detection and isolation scheme is studied for satellite system subject to actuator faults, external disturbances, and parametric uncertainties. The proposed methodology incorporates a residual generation module, including a bank of filters, into an intelligent residual evaluation module. First, residual filters are designed based on an improved nonlinear differential algebraic approach so that they are not affected by external disturbances. The residual evaluation module is developed based on the suggested series and parallel forms. Further, a new ensemble classification scheme defined as blended learning integrates heterogeneous classifiers to enhance the performance. A wide range of simulations is carried out in a high-fidelity satellite simulator subject to the constant and time-varying actuator faults in the presence of disturbances, manoeuvres, uncertainties, and noises. The obtained results demonstrate the effectiveness of the proposed robust fault detection and isolation method compared to the traditional nonlinear differential algebraic approach. [ABSTRACT FROM AUTHOR]

In this paper, we investigate an architecture for autonomous distributed control of braking and driving force on each wheel of a vehicle equipped with in-wheel motors on four wheels. Specifically, in a scenario where the driving force of some wheels is reduced due to low-friction road or motor failure during going straight ahead, the remaining wheels that can generate driving force autonomously control the yaw rate caused by the unbalanced driving force and driving force reduction to maintain the vehicle behavior. To realize autonomous distributed control, we focus on broadcast control from the control theory of multi-agent systems, which deals with the control of systems composed of many elements. We verify by simulation that the proposed architecture performs as desired for the assumed scenario. [ABSTRACT FROM AUTHOR]

In order to study the wheel polygon wear problems in high-speed trains, an iterative model of wheel wear was established based on $ 1) $ 1) the train-track rigid-flexible coupling dynamics model, $ 2) $ 2) Kik-Piotrowiski + Fastsim wheel-rail contact model, and $ 3) $ 3) Archard wear model to predict the developing process of wheel polygon. Taking a certain type of high-speed train in China as an example, the developing process of the 20-order wheel polygon is simulated. Compared with the Hertz model, the results of the Kik-Piotrowiski model are more consistent with the actual situation, and the prediction of the wheel polygon is more accurate. The results show that with the increase of vehicle running speed, the dominant order of the final wheel polygon decreases gradually, while the excitation frequency always locates between 550 and 600 Hz, which verifies the 'frequency fixed' mechanism. By comparing the development of wheel polygon wear results under three working conditions $ 1) $ 1) flexible wheelset + flexible rail, $ 2) $ 2) rigid wheelset + flexible rail, and $ 3) $ 3) flexible wheelset + rigid rail), and by analysing the harmonic response of rail, it is concluded that the third-order bending modal vibration of rail plays an important role in the forming of wheel polygon.. [ABSTRACT FROM AUTHOR]

Wear on the wheel-rail interface has a serious effect on the operation safety and efficiency of heavy-haul freight vehicles. Wheel asymmetric wear (WAW) greatly affects the vehicle's dynamic performance. This paper explores the causes of WAW in heavy-haul freight vehicles and proposes the limit value of the WAW. A dynamic model of heavy-haul freight vehicle is established and the Jendel wheel wear model is used to analyze the mechanisms and influencing factors of WAW. The study primarily focuses on four factors: uneven loading of freight vehicles, differences in wheel surface hardness, suspension errors of the left and right side, and the distribution characteristics of the line. Next, the wheel wear model is verified by the test data, the flange wear and tread wear are analyzed at the same time. The WAW limits value under the load and empty conditions by considering the elastic wheelset model is investigated. The results showed that differences in wheel surface hardness between the left and right wheels and line distribution are the main causes of WAW. By conducting dynamic calculations, the WAW limit value of the empty and heavy vehicle is set as 2 mm. During the operation, it is necessary to effectively monitor the vehicle and track parameters that affect WAW. [ABSTRACT FROM AUTHOR]

The wheel-rail contact asymmetry on the left and right sides of the wheelset while navigating high-speed vehicles through turnouts can lead to lateral motion of the wheelset, ultimately resulting in substantial vibrations in the vehicle system. This study employs the trace method to examine the changing pattern of the wheel-rail equivalent conicity in the turnout area as the wheel profile evolves. A coupled system dynamics model containing flexible turnouts is established. Specifically, the model examines the lateral position of wheel-rail contact points, the lateral motion of the wheelset, and the lateral vibration acceleration of the vehicle system. The study indicates that the lateral motion characteristics of high-speed trains passing through turnouts are influenced by the degree of wheel wear. When the wheels are slightly worn (for mileage below or equal to 100,000 km), the lateral dynamic responses of the vehicle system are affected by the inherent structure of the turnout. When the wheels are severely worn (for mileage above or equal to 150,000 km), the lateral dynamic response of the vehicle system is no longer affected by the inherent structure of the turnout. [ABSTRACT FROM AUTHOR]

The rail side wear in small radius curved track of metro lines is a serious problem in railway maintenance, which reduces the curve passing performance and shortens the service life of the wheel and rail. To improve the vehicle's curve passing performance and reduce rail wear, a localized grinding profile design method for sharp curves was developed. The GFC profile generation method was used to generate the profiles for the curved track of the metro line. Then a metro vehicle-track dynamic model was established to calculate the wheel rail contact parameters, objectives and constraints. The profiles are optimized by the KSM-PSO optimization algorithm. Finally, a simulation analysis of the curve passing performance and wheel-rail wear of the optimized profile was carried out. When the metro vehicle passes through the curved track with a curve radius of 450m, the optimized rail profile can effectively reduce the wear of the rail, the wear of the high rail in the curved track is reduced by 20.18%. The localized rail grinding of the curved track can effectively reduce the rail side wear, the GQI index is also significantly improved. This study can guide the design of rail grinding profiles for the metro lines. [ABSTRACT FROM AUTHOR]

The dynamic interaction between the vehicle and track is strongly influenced by out-of-round wheels and turnout rail profile geometries, which result in high-magnitude contact forces and abnormal vibrations. This study presents the dynamic response of the tram-turnout interaction due to polygonal wheel wear and analyses its transmission between the wheelsets. A three-dimensional coupled tram-turnout dynamic model was formulated, taking into account the polygonal wear on the front bogie wheelsets. Through numerical simulations, the dynamic characteristics of a tram passing through the turnout switch and crossing panels under the influence of polygonal wear were simulated. Furthermore, the impact of polygonal wear amplitudes and tram speeds on the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer bogie wheels are described. According to the numerical findings, when the flexible wheelset experiences polygonal wear, it can lead to substantial impact forces and vibrations as the tram moves through the turnout switch and crossing zones. Moreover, the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer wheels increases as the wheel wear amplitude and the vehicle speed increase. [ABSTRACT FROM AUTHOR]

Timely monitoring of wheel polygon is of great importance for the formulation of railway wheel maintenance strategies. In this study, a novel data-driven method for onboard and quantitative detection of wheel polygon is presented. First, the axle box acceleration (ABA) signal preprocessing method and stationarity test are introduced to select the relatively stationary signal from the measured data of ABA. Next, an iterative algorithm is developed to accurately extract the quasi-stationary ABA signals, representing each wheel rotation period. Then, an improved frequency domain integration method is developed to quantitatively capture the orders and roughness levels of the wheel polygon. Finally, the effectiveness and superiority of the proposed method is verified using the field-measured data of ABA and the wheel polygon in one cycle of wheel re-profiling. The results show that the proposed method can quantitatively capture the dominant characteristics of single- and multi-orders wheel polygons at different operating mileages with minimum and maximum absolute errors of 0.04 dB re 1 µm and −2.33 dB re 1 µm, respectively. The comparative analysis demonstrates that the proposed method outperforms the traditional time and frequency domain integration algorithms in the detailed characterisation of wheel polygon roughness levels. [ABSTRACT FROM AUTHOR]

Railroad turnouts are an essential element of the track infrastructure that facilitates the movement of trains between adjacent or diverging tracks. Turnout frogs are subjected to high wheel impact forces due to the inherent need for a discontinuity in their geometry. To develop an optimised frog geometry to minimise wheel impacts, a parametric study was designed and executed that considered three critical design parameters: point (i.e. nose) slope, relative height difference between wing and point, and longitudinal wing slope. Four hundred wheel profiles were extracted from a dataset of one million revenue service wheel profiles based on a wheel classification methodology previously developed. Wheel impact was quantified for each frog geometry case based on wheel transfer distribution and vertical wheel trajectory which were analysed using a developed Python algorithm. A total of 30 unique geometries were evaluated, including the existing standard design geometry for a N.A. heavy point conformal frog. Results demonstrated that each parameter affects different locations along the frog and total impact is most affected by point slope. Lastly, an optimised frog geometry was selected that ensures well-distributed wheel transfer locations preventing the concentration of damage, and results in low total impact at the transfer point. [ABSTRACT FROM AUTHOR]

The high-speed turnout is a key part of railway track infrastructure. A process of wheel-load transition and single-wheel/multi-track contact take place in the turnout area, causing significant wheel-rail interaction. Most high-speed turnouts include movable-point crossings. To investigate the wheel-rail transient rolling contact behaviour in movable-point crossings, a 3D finite element (FE) model of a wheelset rolling over a crossing was introduced. The actual geometrical profile of the wheel and the rails in turnouts, the nonlinear materials, the actual relative motion between the point/wing rail, and the moving postures of the wheelset were considered. The simulated mode shape was compared with the experimental mode shape to verify the wheel-rail coupling model. Precise frictional rolling contact solutions and dynamic response, including wheel-rail force, contact stress, equivalent stress, equivalent plastic strain, and stick-slip distribution of the contact patches, were all studied. After this, the parametric analysis of dynamic wheel-rail contact behaviour was carried out. The simulated results indicate that the proposed explicit finite element method can characterise wheel-rail coupled dynamic interaction and mesoscopic rolling contact behaviour well, and improve the understanding of wheel-rail contact behaviour in the movable-point crossing panel of the high-speed turnouts. [ABSTRACT FROM AUTHOR]

The mechatronic vehicle developed within the Shift2Rail projects Run2Rail, Pivot, NEXTGEAR, and Pivot2 is evaluated with respect to wheel wear. The KTH wear model is used to determine the coefficients of Archard's wear map to reproduce measured worn wheel profiles of the present vehicle running on Metro Madrid line 10. The same wear model is then used to evaluate the performance of the mechatronic vehicle controlled with two variants of a feedforward controller. The first one uses on-board measurements, while the second one is optimised using firefly optimisation algorithms assuming knowledge of the travelled track. The control strategy based on on-board measurements shows improvements above 60% in terms of lost wheel volume due to wear, compared to the standard bogie vehicle. The optimised controller reaches improvements above 70%. Good coherence is found between improvements predicted with the wear number and the ones achieved in terms of lost wheel volume. [ABSTRACT FROM AUTHOR]

Small-radius wheels are gradually introduced on special rail vehicles, such as double-decker coaches and piggyback wagons. It allows for a low-floor design and further increases the loading capacity of vehicles. From the perspective of vehicle dynamics, small-radius wheels have lower unsprung mass than the nominal wheels with a radius of 460 mm, and it could mitigate the wheel-rail dynamic interaction. Also, the contact patch size is reduced due to the increased curvature of the rolling contact circle, and they are more sensitive to changes in the track geometry than nominal wheels, especially in turnouts with discontinuous rail profiles. To investigate the dynamic response of small-radius wheels in a turnout, the Manchester Benchmark passenger coach with variable radius wheels and a left-hand turnout with a radius of 245 m are introduced in this work. The influence of wheel radii on the running performance, including the wheel-rail interaction and wheel damage behaviour, is investigated by numerical simulations. In addition, a sensitivity study is executed to evaluate the influence of unsprung mass and wheel flange friction on the performance of a vehicle whose wheel radius is 275 mm, and the potential remedy to mitigate high wheel wear is proposed. [ABSTRACT FROM AUTHOR]

A rotor dynamic model of wheel-rail coupling system was established taking wheel eccentricity and initial polygon into consideration in order to investigate the mechanism of wheel polygonal wear. Considering the complex wheel-rail contact relationship, the equivalent yaw angle was proposed and the wheel-rail relative speed model was established. The law of wheel-rail self-excited vibration and its effect on polygonal wear were studied. The possibility of variable speed operation was investigated together with the sensitivity of the system parameters. The results show that the periodic longitudinal and lateral creep forces are essential for the wheel polygonal wear, which have the characteristics of supercritical Hopf bifurcation and 'fixed wavelength' and 'fixed frequency'. While in some circumstances, longitudinal and lateral creep forces jointly cause polygonal wear, in other cases, longitudinal creep forces have almost no effect. By adjusting the longitudinal and lateral stiffness, primary suspension stiffness, and rail damping parameters, as well as by selecting an appropriate speed for variable speed operation, the wheel polygonal wear may be effectively suppressed. The findings offer a fresh viewpoint for the study of mechanisms and the prevention of wheel polygonal wear. [ABSTRACT FROM AUTHOR]

A successful predictive maintenance strategy for wheels and rails depends on an accurate and robust modelling of damage evolution, mainly uniform wear and Rolling Contact Fatigue (RCF). In this work a life prediction framework for wheels and rails is presented. The prediction model accounts for wear, RCF, and their interaction based on the output from MBS simulations to calculate the remaining life of the asset, given in mileage for wheels and MGTs for rails. Once the model is calibrated, the proposed methodology can predict the sensitivity of the maintenance intervals against changes in operational conditions, such as changes in contact lubrication, track gauge, operating speeds, etc. The prediction framework is then used in two operational cases on the Swedish Iron-Ore line. The studied cases are, the analysis of wheel life for the locomotives, and the analysis of rail life for gauge widening scenarios. The results demonstrate the capabilities of the MBS-based damage modelling for predictive maintenance purposes and showcase how these techniques can set the path towards Digital Twins of railway assets. [ABSTRACT FROM AUTHOR]