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Identifying a spectral frequency band with abundant fault information from spectral coherence is essential for improved envelope spectrum-based bearing diagnosis. Both blind features and targeted features have been employed to distinguish informative spectral frequency band of spectral coherence. However, how to select appropriate feature to correctly discriminate the optimal frequency band of spectral coherence in different scenarios is problematic. In this study, a new targeted feature is presented to quantify the signal-to-noise ratio in narrow frequency bands of spectral coherence, and further a method based on the proposed feature is developed to distinguish an optimal spectral frequency band of spectral coherence for bearing diagnostics. The efficiency of the developed method, typical blind feature-based methods and typical targeted feature-based methods in identifying the defect-sensitive frequency band of spectral coherence and bearing fault diagnosis is validated and compared using simulated signals with different interference noises and bearing experimental signals. The advantages and limitations of typical blind and targeted feature-based methods in different scenarios are summarized to guide the application. The results demonstrate that the developed targeted feature can efficiently evaluate bearing failure information in the cyclic frequency domain, and the presented approach can accurately discriminate the failure-related spectral frequency band of spectral coherence and detect different bearing faults compared with the methods based on the state-of-the-art features.

Morphological filtering has been extensively applied to rotating machinery diagnostics, whereas traditional morphological operators cannot effectively extract fault-triggered transient impulse components from noisy mechanical vibration signal. In this paper, a framework of generalized compound morphological operator (GCMO) is presented to enhance the extraction ability of impulsive fault features. Further, several new compound morphological operators are developed for transient impulse extraction by introducing the product, convolution, and cross-correlation operations into the GCMO framework. In addition, a novel strategy for selecting the structural element length is proposed to optimize the repetitive impulse feature extraction of the compound morphological operators. The fault feature extraction performance of the developed compound morphological operators is investigated and validated on the simulation signals and measured railway bearing vibration signals, and compared with the combined morphological operators and five existing feature extraction methods. The results demonstrate that the morphological cross-correlation operators are more efficient in repetitive fault impulse feature extraction and bearing fault diagnosis than the combined morphological operators and the comparison methods.

Purpose This paper aims to study the electric sliding wear performance of a rigid overhead line/contact strips and to find an optimal overhead line/contact strip pair to minimize the wear of the contact strip under direct current (DC) passage. Design/methodology/approach The tribological characteristics of an overhead line against four contact strips with DC were experimentally investigated using a block-on-disc tester. The wear and temperature of the contact strips were collected and analysed. The severe wear mechanism of the contact strips was discussed. Findings Using Taguchi’s method, DC was found to be the most important factor affecting the wear and temperature of current collectors, the normal force being the second and the sliding velocity the weakest. The abnormal wear of current collectors was attributed to arc ablation and poor thermal stability of collectors. The wear performances of current collectors could be optimized by matching different Cu-impregnated carbon strips with the Cu–Ag wire and the wear of current collectors could be reduced by selecting the appropriate normal force, DC and sliding velocity. Originality/value Among all test parameters such as the DC, normal force, sliding speed and collector type, DC was identified as the most important factor affecting the wear and temperature of contact strips for the first time. The arc ablation and thermal stability of collectors were considered to be two main factors affecting the wear of the collectors.

It is a practical engineering problem to lift the pantograph during train operation. In this paper, a pantograph-catenary (PAC) model is established, which can realize pantograph lifting during train operation. In this model, the contact model between contact piece and contact wire is established using the polygon contact model (PCM). The PAC collision test rig is established, and the simulation model at low speed is verified by comparing the contact force and vertical acceleration of contact piece obtained from simulation and test. The factors influencing the process of pantograph lifting are analyzed. The simulation results show that the position where the dropper and contact wire are connected is the most disadvantageous position for pantograph lifting. The maximum impact force increases with the increase of pantograph lifting speed, and the relationship between them is linear. In addition, if the influence of aerodynamic force is not considered, the running speed of vehicle will not affect the pantograph lifting process.

This paper studies the influence of lateral and local rail deformation on the train–track interaction dynamics in high-speed railways. While the traditional method ignores the curvature of a latera...

An extended pantograph-catenary (PAC) contact collision model is presented in this paper. The catenary is described by a finite element model while the pantograph is described by a multi-body model. The normal collision model is established by using the Hertzian contact theory. A 1:1 PAC collision contact test rig is built to validate the pantograph-lifting model. The dynamic responses of the PAC system during lifting the pantograph with different velocities and positions are studied. The research results show that the velocity and position of lifting the pantograph will affect the pantograph-lifting time, acceleration of collector piece, vertical displacement and contact force in the process of lifting pantograph. When the velocity of lifting the pantograph exceeds 0.5 m/s, the contact force between the pantograph and the contact wire will exceed 250 N, which is the allowed value set in the provisions of EN50367. It is essential to control the velocity of lifting the pantograph below 0.4 m/s to prevent the catenary or contact piece from being damaged due to the excessive impact force. The distribution of the droppers also affects the collision force between the PAC system.

A complete track-vehicle-pantograph-catenary (TVPC) coupling dynamics model is presented and several elaborate simulation cases are set to analyse the effect of vehicle body vibration on the pantog...

To analyse and simulate the dynamic responses of the gearbox in a vehicle–track system, a three-dimensional vehicle–track coupled dynamics model for high-speed trains has been developed in this study with a comprehensive consideration of the transmission system. Using this dynamics model, the coupling effects between the gearbox housing and its connected components were analysed. Based on the dynamic results, the dynamic stress field of the gearbox housing can be obtained using the finite element methods. The model outputs were successfully validated through comparisons with field test data. Following model validation, the dynamic stress and its distribution throughout the gearbox housing were further investigated under different excitations, including track irregularities, wheel polygonal wear and flatness. The results demonstrate a significant increase in the stress levels of the oil level window aperture and the bottom face of the housing, which coincides with the location of cracks that are formed in the gearbox housing during frequent vehicle operation. While a specific case has been studied here, the proposed dynamics model can be applied to related dynamic assessments, such as vibration or suspension parameter analyses, as well as to stress analyses of any rail vehicle transmission system to guide the maintenance and design.

As an important component of a high-speed train motor car, the traction transmission system, which directly affects the dynamic performance and the running safety of the vehicle. The present paper establishes a comprehensive spatial coupled dynamics model of the motor car–track system. The model is based on classical vehicle–track coupled dynamics and gear dynamics theory. The coupling effects between the traction transmission subsystem and the vehicle–track system are captured by the suspension system, gear mesh, and wheel–rail interactions. Some nonlinear factors, such as the nonlinear damping characteristics, the gear time-varying mesh stiffness, and the wheel–rail contact relationship, are considered. The results of the proposed dynamics model are compared with those of experimental field tests for validation, which reveals the dynamics performance of the whole system, particularly the dynamics of the traction transmission system in vehicle-coupling vibration environments. The traction transmission exerted non-negligible effects on the wheelset vibrations and the wheel–rail interface, especially in the low-speed range. Furthermore, this dynamics model can assess the vibrational characteristics of the coupled system under the complex excitations that occur during service, such as gear cracking, wheel defects and rail local defects, particularly during the acceleration process.

A three-dimensional vehicle-track coupled dynamics model, with the inclusion of the axle-box bearings, has been developed, which considers the coupling effects between the bearing and the vehicle c...

The gear transmission system of a high-speed train is the key component, which delivers the traction torque from the motor to the wheelset. It couples with the vehicle system via the suspension system, gear meshing and the wheel–rail interface. The dynamic performance of the transmission system directly affects the operational reliability or even the running safety of high-speed trains. In this study, the effects of wheel polygonalisation and wheel flat on the dynamic responses of the transmission system are investigated through simulations of a novel vehicle dynamics model. This model integrates the flexible gearbox housing, the time-varying mesh stiffness and the nonlinear gear tooth backlash, and the track irregularities to obtain more realistic responses of the traction transmission systems in a vehicle vibration environment, from motors to wheelsets, under the effects of the wheel flat and polygonal wear. The field experimental tests are implemented for a vehicle running along a main high-speed railway line in China. Subsequently, the developed dynamics model is validated with good agreement between the experimental and the theoretical results. The calculated results revealed that wheel flat and wheel polygonal wear caused a high-frequency fluctuation of both the longitudinal creep force and the gear mesh force, causing a violent and complex torsional vibration of the gear transmission system. Moreover, the flexible deformation of the gearbox housing, especially its resonance due to the wheel polygonal wear, contributed to the torsional vibration of the gear transmission system.

This paper describes an impact detection system using strain signals based on fibre optic sensors(FBG) for the real-time monitoring of the catenary system. The proposed detection system consists of...

In general, the electrical energy is provided to the high-speed train through the pantograph-catenary sliding contact. The variation of the dynamic contact force is expected to be small enough to keep the good current collection quality and to extend the service life of the pantograph-catenary system. In this paper, the two tension wires of the catenary are discretized by the sine-series expansions, a multibody dynamics theory based on relative coordinates is adopted to describe the dynamic behavior of the pantograph, and the standard deviation (STD) of dynamic contact force is used as the indicator to evaluate the contact quality. The objective is to investigate how the variations of the pantograph’s main structure influence the contact quality, which may support the structural design and parameter optimization of the pantograph in high-speed railway.

Rail corrugation on low rails of sharp railway curves is still a difficult problem to solve worldwide. Nearly all low rails of the sharp railway curves incur rail corrugation. In the present study, an active method to remedy rail corrugation was studied. From the viewpoint of the frictional self-excited oscillation of a wheelset-track system causing rail corrugation, the effect of wheelset structures on rail corrugation was studied. Three frictional self-excited oscillation models of wheelset-track systems with different wheelset structures were established, which include a heuristic wheelset structure and two being used in the railway industry. The incidence trends of the self-excited oscillations of these three wheelset-track systems were studied. It was found that the wheelset structure has an important effect on rail corrugation, and that the heuristic wheelset structure can restrain or get rid of rail corrugation. With the parameter sensitivity analysis, it was found that when the friction coefficient between the wheel and rail, rail gauge, rail cant, and sleeper span changes to some extent, the heuristic wheelset structure is robust enough to prevent rail corrugation. The proposed heuristic wheelset structure can be used as a potential solution to rail corrugation on sharply curved tracks.

Optimization design for pantograph-catenary system is of great significance to keep the good current collecting quality. As the main parameters of pantograph’s upper frame, stiffness and damping need to be well designed, especially in the high speed operation condition. Based on the relative coordinate theory in multibody dynamics, this paper proposed a new simplified method to simulate the flexible characteristic of the upper frame in pantograph-catenary interaction. In this method the upper frame is divided into several segments, which are articulated with torsion springs. The flexibility change of the upper frame is described by the key parameter variation of these torsion springs. In the pantograph-catenary coupling system, finite element method (FEM) is applied to establish the model of catenary, Hertz contact theory is adopted and the standard deviation (STD) of the contact force is used as an evaluation index. Sensitivity of the upper frame’s flexibility to current collecting quality is given, which will effectively support for the structural design and material selection of the upper frame of pantograph adapting to different train operation speeds.

Dynamics of a long beam on the elastic foundation subjected to moving loads is studied in the present paper. The sliding window technique is used to dynamically truncate the long beam and a reduced time-varying beam system is obtained. The Hamilton’s principle is employed to establish the equations of motion of the reduced system. The variable separation method is adopted to solve dynamical responses of the reduced system. Examples of a long simply supported Timoshenko beam on the nonlinear foundation subjected to a single moving load and multiple loads are included. Numerical results of the reduced model compared with the ones obtained from the moving element model adapted in literature are carried out to show the validity and the good efficiency of the method proposed in the present paper.

The application of electrified railway directly promotes relevant studies on pantograph-catenary interaction. With the increase of train running speed, the operating conditions for pantograph and catenary have become increasingly complex. This paper reviews the related achievements contributed by groups and institutions around the world. This article specifically focuses on three aspects: The dynamic characteristics of the pantograph and catenary components, the systems’ dynamic properties, and the environmental influences on the pantograph-catenary interaction. In accordance with the existing studies, future research may prioritize the task of identifying the mechanism of contact force variation. This kind of study can be carried out by simplifying the pantograph-catenary interaction into a moving load problem and utilizing the theory of matching mechanical impedance. In addition, developing a computational platform that accommodates environmental interferences and multi-field coupling effects is necessary in order to further explore applications based on fundamental studies.

This study investigates the effects of polygonal wear of wheels on the dynamic performance of the gearbox housing of high-speed trains. First, a dynamics model of the driving system is developed considering gear meshing and flexible deformation of the gearbox housing. Responses of the gearbox housing are calculated using the modal superposition method. Then, a multibody dynamics model of a railway motor car is established considering the driving system. Rig tests in the laboratory and field experiments on the Beijing–Shanghai high-speed rail line are, respectively, performed. Based on the simulation and experiments, the dynamic characteristics of the gearbox housing of the motor car are analysed. The results of the analysis show that polygonal wear can significantly influence the vibration of the gearbox housing, and the maximum amplitude of the acceleration of vibration is more than 200 g. In addition, resonance of the gearbox housing occurs due to the 20th-order polygonal wear. In the resonance region, the oil level sight glass of the gearbox housing vibrates severely, contributing immensely to its cracking.

The impact of voltage on the electric sliding tribological properties of collectors gliding against overhead lines was experimentally investigated exploiting a block-on-disk test rig. The coefficient of friction, abrasion rate of collectors, temperature of the collectors and overhead lines, arc energy, and current-passing efficiency were collected or evaluated. The scar surfaces of current collectors were observed by SEM and analyzed by EDS. Results show that the voltage has a significant impact on the electric sliding tribological properties of collectors rubbing against overhead lines. The wear rate and temperature of collectors, and the arc energy all increase as the voltage increases. The influence mechanisms of voltage on the wear properties of collectors against overhead lines with current were also discussed.

Active control of pantograph is a promising approach in improving the current collection quality of high-speed railway pantograph-catenary system. To address the shortcomings of the lumped-parameter pantograph model used in previous studies, a multi-body model of pantograph is established, and two configurations of installing actuators on a multi-body pantograph are presented. In combination with a nonlinear finite element model of catenary, the control performance is evaluated through several numerical simulations. First of all, the effect of control gains on the control performance is analyzed. Then considering more realistic conditions, the controller time-delay and the limitation of controller sensitivity are included, whose influence on the control performance is investigated. At last, considering realistic external disturbance (strong wind load and locomotive vibration) to pantograph-catenary system the control performance is evaluated in decreasing the fluctuation in contact force as well as eliminating the contact loss. The results indicate that the proposed controller with larger control gains has better performance in decreasing the fluctuation of the contact force between the multi-body pantograph and the nonlinear finite element catenary, but has lower robustness against the controller time-delay. The reduction of controller sensitivity results in a fluctuating degradation of the control performance.

This paper proposes a dynamic equilibrium method for finding the initial equilibrium configuration of a railway catenary. In the proposed method, the catenary composed of flexible wires is modeled using two-node cable elements with absolute nodal coordinates based on a flexible multibody system formulation. Dynamic conditions that characterize the initial equilibrium configuration of the catenary are given and addressed as control processes in the form-finding procedure. The key feature of the proposed method is that the catenary configuration is continually evolved by dynamic simulation until characterization conditions are attained and an equivalent configuration of the centenary at static equilibrium is thus computed. It is validated using two examples and applied to the form-finding analysis of a two dimensional simple railway catenary. The obtained results are analyzed and discussed. It is general and can be applied to catenaries with complex configurations.

The tribological performance of metro rigid overhead lines against pantograph sliders was experimentally studied. The test parameters from actual metro lines were adopted. During testing, the friction force, wear volume, temperature, vibration of the pantograph slider, voltage drop, and current correlating with arc ablation were collected. The worn topography of the slider and wire was observed. Experimental results illustrate that the direct current (DC) and vibration of the slider can largely affect the tribological performance of the rigid overhead line against the pantograph slider. Main wear mechanisms are the arc ablation, plowing wear and adhesive wear. The abnormal joint between two slider blocks can bring about severe plowing wear of the overhead line.

An efficient Timoshenko beam model of finite length is developed for train-track interaction dynamics. The rail is reduced to the present beam model and its vertical and lateral bending, shear, and torsion deformations are considered. A moving control volume attached to the train is introduced, which encloses the reduced rail, and a reference coordinate system is established in the reduced rail at the left end. The arbitrary Lagrangian-Eulerian (ALE) method and the modal superposition method (MSM) are adopted, and governing equations of the reduced rail model are derived by Lagrange's equations. Owing to the advantages of the MSM, the number of degrees of freedom of the current formulation is clearly reduced and its efficiency is greatly improved. A long non-ballasted track of finite length subjected to a constant moving load is first considered, and results from the present beam model are in good agreement with those from the traditional finite element method. A three-dimensional train-track interaction problem with consideration of a ballasted track is further studied. Results from the present beam model are compared with those from the commercial software Simpack where the MSM is used, and they are in good agreement with each other. Since the number of modes in the present beam model is much fewer than that in Simpack, the present beam model is more efficient than that in Simpack. It is found that the number of shape functions and the length of the beam model used in calculation can significantly affect the accuracy and efficiency of the present beam model, which should be taken into consideration. The current beam formulation is independent of the moving velocity of the train and can handle train-track dynamics with variable train velocities. The current beam formulation is straightforward and can be easily extended in various complex applications. It is more suitable for dealing with long-term train-track interaction dynamics.

Field investigations have demonstrated that the wear life of a carbon slider of a pantograph in a high-speed train of the 250 km/h speed class is very short. In this study, several experimental tests were performed on a high-speed test machine to understand the mechanisms of the serious wear of the slider against the wire under electric current. The experiments on the high-speed railway were carried out at electric currents of 200, 300, 400, and 500 A, sliding speeds of 100, 150, 200, and 250 km/h, and normal loads of 60, 80, 100, and 120 N. The friction coefficient, wear volume, arc electric current, arc electric voltage drop, and temperature increase of the carbon slider were recorded and analyzed. The experimental results demonstrated that the wear volume of the slider increased with the electric current and that arc melting and thermally enhanced wear were the dominant mechanisms causing the serious wear of the slider.

Blind deconvolution is a method for enhancing the fault feature of rolling element bearings. Based on different maximization criteria, including kurtosis, correlated kurtosis, D-norm, multi-D-norm, and cyclostationarity indicator, different blind deconvolution algorithms have been proposed as powerful tools for fault feature extraction. However, kurtosis and D-norm are susceptible to extreme values, while the other three criteria strongly rely on prior knowledge of the fault period. To overcome the shortcomings of the existing criteria, this study proposes a new criterion called impulse-norm. It is a time-domain parameter defined as the ratio of the average amplitude of the first several maximum energy points to the energy of the entire signal. As opposed to kurtosis and D-norm, the impulse-norm is not affected by strong random impulses. Unlike correlation kurtosis, multi-D-norm and cyclostationarity indicator, it is also independent from the fault period. Based on impulse-norm, we also propose a new deconvolution algorithm called particle swarm optimization-based maximum impulse-norm deconvolution. This blind deconvolution algorithm employs generalized sphere coordinate transformation and adopts the PSO algorithm to optimally solve the filter coefficients by maximizing the impulse-norm of the signal being filtered. The proposed method was validated using simulated signals and high-speed train axle-box bearing experimental signals. The simulation and experimental results indicated that the proposed PSO-MIND method can effectively identify the weak impulse fault feature of rolling element bearings.

The induced airflow velocity level and the mechanical efficiency are the significant issues for the surface DBD flow control application. In this paper, the effects of optical characteristics, electrical performances and mechanical properties of surface DBD with composite dielectric glass/PI film are investigated. The current, discharge plasma morphology, electrical power consumption, and induced airflow velocity are analyzed at applied voltage 17-23 kV with working frequency 9.15 kHz. The experiment results indicate that with the addition of PI film, the discharge just occurs near the exposed electrode and is suppressed obviously in the negative half cycle of current. Though the induced airflow velocity decreases slightly about 0.1-0.2 m/s at each voltage level, the mechanical efficiency substantially improves. The maximum mechanical efficiency increases by 25.12% under the 23 kV.The induced airflow velocity level and the mechanical efficiency are the significant issues for the surface DBD flow control application. In this paper, the effects of optical characteristics, electrical performances and mechanical properties of surface DBD with composite dielectric glass/PI film are investigated. The current, discharge plasma morphology, electrical power consumption, and induced airflow velocity are analyzed at applied voltage 17-23 kV with working frequency 9.15 kHz. The experiment results indicate that with the addition of PI film, the discharge just occurs near the exposed electrode and is suppressed obviously in the negative half cycle of current. Though the induced airflow velocity decreases slightly about 0.1-0.2 m/s at each voltage level, the mechanical efficiency substantially improves. The maximum mechanical efficiency increases by 25.12% under the 23 kV.

The pantograph was respectively simplified as several different mathematical models, including a lumped mass model, a rigid model, a rigid-flexible hybrid model and a full flexible model. The simulation model of pantograph-catenary system was established and analyzed. The dynamic characteristics were presented, including the contact forces, the accelerations and the corresponding spectra, etc. Subsequently, a comparison of the simulation results of the contact forces with test data was performed. For the different pantograph models, it is proved that there is some difference in the dynamic characteristics, and the rigid-flexible hybrid pantograph model is more reasonable to analyze the dynamic behavior of pantograph and catenary system.

Axle box bearings are the most critical mechanical components of railway vehicles. Condition monitoring is of great benefit to ensure the healthy status of bearings in the railway train. In this paper, a novel fault diagnosis model for axle box bearing based on symmetric alpha-stable distribution feature extraction and least squares support vector machines (LS-SVM) using vibration signals is proposed which is conducted in three main steps. Firstly, fast nonlocal means is used for denoising and ensemble empirical mode decomposition is applied to extract fault feature information. Then a new statistical method of feature extraction, symmetric alpha-stable distribution, is employed to obtain representative features from intrinsic mode functions. Additionally, the hybrid fault feature sets are input into LS-SVM to identify the fault type. To enhance the performance of LS-SVM in the case of small-scale samples, Morlet wavelet kernel function is combined with LS-SVM for the classification of fault type and fault severity and the particle swarm optimization is used for the optimization of LS-WSVM parameters. Finally, the experimental results demonstrate that the proposed approach performs more effectively and robustly than the other methods in small-scale samples for fault detection and classification of railway vehicle bearings.

The paper is aimed at developing an optimized design of the pantograph and catenary system with double pantographs at a speed of 350 km/h for the Wuhan-Guangzhou high-speed railway. First, the pantograph and catenary system for the Beijing-Tianjin high-speed railway was analyzed to verify whether its design objective could be fulfilled. It shows that the system is not able to satisfy the requirement of a sustainable running speed of 350 km/h. Then a new scheme for the pantograph and catenary system is proposed through optimization and renovation of the structure and parameters of the pantograph and catenary system, including the suspension type of the catenary, tension of the contact wire, and space between two pantographs. Finally, the dynamic performance of the new system was verified by simulation and line testing. The results show that the new scheme of the pantograph and catenary system for the Wuhan-Guangzhou high-speed railway is acceptable, in which the steady contact between the rear pantograph and the catenary at the space of 200 m can be maintained to ensure the current-collection quality. A current collection with double pantographs at a speed of 350 km/h or higher can be achieved.