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Purpose. The scientific work is intended to develop a methodology for describing the structure of the railway vehicles (they are considered as a system of rigid bodies connected by rigid, elastic and dissipative elements), which would allow us to obtain the equations of motion in an easily algorithmized way. Methodology. When constructing the model, authors tend to ensure that its structure reflects the structure of the mechanical system, that is, parts of the model must correspond to parts of the car. In this case, the model takes the form of a hierarchically organized graph whose vertices correspond to the bodies, attachment points of the connecting elements and to the connecting elements themselves, and the edges describe the sets of processes that are related to the incident vertexes. As a rule, these are movements and forces: for the edge between the body and the attachment point they are generalized movements of the body and the general forces acting on it; for the edge between the attachment point and the connecting element - the movements of the point and the forces arising in the element. To each vertex there corresponds a group of equations describing the motion of the system. The nature of the equations depends on the type of the vertex. For the body it is the equations of body motion; for the point - the expressions for the point displacements through generalized displacements of the body and generalized forces acting on the body, through the forces arising in the connecting element; for the connecting element - the expression for the forces arising in it through the deformation of the element. The graph can be regarded as oriented. The direction of the edge is chosen in such a way that for each vertex the values on the right-hand side of the vertex-associated equation would correspond to the incoming edge, and in the left-hand side - to the outgoing edge. Findings. A technique for constructing a dynamic model of oscillations of railway vehicles as a system of rigid bodies is developed on the basis of their description using hierarchically organized graphs. The technique was tested to construct a model of spatial oscillations of a 4-axle freight car with an axial load of 25 tons in Simulink package. Originality. For the first time, a technique has been developed for describing the structure of a railway vehicle using a hierarchical graph, which makes it possible to obtain equations of motion in an easily algorithmized manner. Practical value. The proposed methodological approach will allow, after creating a library of bodies and connecting elements, to significantly reduce the time spent on modeling the oscillations of different vehicles.

Temperature effects on the generation of brake wear particles from railway vehicles were generated, with a particular focus on the generation of ultrafine particles. A real scale brake dynamometer test was repeated five times under low and high initial temperatures of brake discs, respectively, to obtain generalized results. Size distributions and temporal patterns of wear particles were analyzed through visualization using clustered heatmaps. Our results indicate that high initial temperature conditions promote the generation of ultrafine particles. While particle concentration peaked within the range of fine sized particles under both low and high initial temperature, an additional peak occurred within the range of ultrafine sized particles only under high initial temperature. The timing of peak occurrence also differed between low and high initial temperature conditions. Under low initial temperature fine sized particles were generated intensively at the latter end of braking, whereas under high initial temperature both fine and ultrafine particles were generated more dispersedly along the braking period. The clustered correlation heatmap divided particle sizes into two groups, within which generation timing and concentration of particles were similar. The cut-off point between the two groups was approximately 100 nm, confirming that the governing mechanisms for the generation of fine particles and ultrafine particles are different. [ABSTRACT FROM AUTHOR]

Background: Active lateral suspension (ALS) technologies have been well developed for several decades, but they have not been widely used in service operation due to relatively high costs for implementation and maintenance and concerns about fail-safe. Therefore, this paper suggests a more practical approach for the active suspension system, designed to achieve target performance with easy implementation and maintenance and high fail-safe. Methods: The control performance target and actuator type are determined from the vibration energy that the ALS has to absorb along the weight function for ride quality evaluation. The installation position of actuator and sensor is decided to decrease the time that it takes for field engineers to check the actuator for maintenance. In addition to fail-safe function of ALS system, conventional hydraulic lateral damper is installed in parallel with ALS to reduce the concern about fail-safe of the ALS. Results: Through the roller rig and filed tests, the performance of the proposed ALS was validated. Lateral ride quality was improved 7.1dB and 6.7dB in the roller rig test and field test, respectively. The fail-safe strategy was also verified during the filed test. Conclusion: Test results show that the suggested ALS is designed appropriately and can be used in practical implementation. [ABSTRACT FROM AUTHOR]

In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively, this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the carriage, and establishes a vertical dynamic model of railway vehicles by considering the influence of the coupling vibration effect between the passenger and the car body. The correctness of the model is verified by the real vehicle test. Then, the influence of the passengers on the vertical vibration characteristics of railway vehicles is analyzed, and the influence of the railway vehicle vibration on the vertical vibration characteristics of passengers is discussed in this paper. The research made in this paper can provide an effective model reference for the analysis of the vertical random vibration characteristics of railway vehicles and passengers, and for the optimization design of the suspension system parameters. [ABSTRACT FROM AUTHOR]

The topic of reducing structural vibrations in the case of flexible carbodies of railway vehicles has been intensively studied, but it is still an active research topic thanks to the importance of the perspective of improving the ride comfort. However, no study has been identified in the specialty literature to feature the contribution of the vibration structural modes upon the vibration behaviour of the railway vehicle carbody. The structural vibration modes of the flexible carbodies are particularly complex; however, the first vertical bending mode holds great significance in terms of the ride comfort. This paper analyses the influence of the first vertical bending mode on the vibration behaviour in three reference points of the railway vehicle carbody in correlation with the carbody flexibility, the vehicle velocity and the suspension damping. This study relies on comparisons between the results of the numerical simulations obtained for a ‘flexible carbody’ type model of the vehicle and the ones obtained for a ‘rigid carbody’ type model. The first part of this study analyses the characteristics of the vertical vibrations behaviour of the flexible carbody based on the dynamic response of the vehicle and expressed as the acceleration power spectral density. In the second part, the influence of the vertical bending on the vertical vibrations level of the carbody is analysed using the root mean square of the vertical acceleration.

Train running safety is considered one of the key criteria for advanced highway trains and bogies. While a number of existing research studies have focused on its measurement and monitoring, this study proposes a new and effective train running a safety prediction framework. The wheel derail coefficient, wheel rate of load reduction, and wheel lateral pressure are considered the decision variables for the safety framework. Data for actual measured rail conditions and vibration-based signals are used as the input data. However, advanced trains and bogies are influenced more by their inertial structures and mechanisms than by railway conditions and external environments. In order to reflect their inertial influences, past data of output variables are used as recurrent data. The proposed framework shares advantages of a general deep neural network and a recurrent neural network. To prove the effectiveness of the proposed hybrid deep-learning framework, numerical analyses using an actual measured train-railway model and transit simulation are conducted and compared with the existing deep learning architectures.

The paper herein analyzes the ride comfort at the vertical vibrations of the railway vehicle, evaluated by two methods—mean comfort method and Sperling’s method. The two methods have in common that the estimation of the comfort sensation is conducted with the comfort indices, namely ride comfort index NMVZ and ride comfort index Wz. The values of these indices are derived from numerical simulations. The advantage of using the results of the numerical simulations versus using experimental results, on which most previous research is based, resides in the fact that the ride comfort indices can be examined while taking into account the influence of velocity and certain parameters altering the behavior of vertical vibrations of the carbody, i.e., carbody flexibility and the suspension damping. The numerical simulation applications have been developed based on a theoretical model of the vehicle that considers important factors affecting the behavior of vertical vibrations of the carbody, by means of a ‘flexible carbody’ type model and an original model of the secondary suspension. The results presented mainly show that the two assessment methods lead to significantly different outcomes, in terms of ride comfort, under identical running conditions of the vehicle.

Railway vehicles are generally operated by connecting several vehicles in a row. Mechanisms connecting railway vehicles must also absorb front and rear shock loads that occur during a train’s operation. To minimize damage, rail car couplers are equipped with a buffer system that absorbs the impact of energy. It is difficult to perform a crash test and evaluate performance by applying a buffer to an actual railway vehicle. In this study, a simulation technique using a mathematical buffer model was introduced to overcome these difficulties. For this, a model of each element of the buffer was built based on the experimental data for each element of the coupling buffer system and a collision simulation program was developed. The buffering characteristics of a 10-car train colliding at 25 km/h were analyzed using a developed simulator. The results of the heavy collision simulation showed that the rubber buffer was directly connected to the hydraulic shock absorber in a solid contact state, and displacement of the hydraulic buffer hardly occurred despite the increase in reaction force due to the high impact speed. Since the impact force is concentrated on the vehicle to which the collision is applied, it may be appropriate to apply a deformation tube with different characteristics depending on the vehicle location.

The paper presents results of a grant research project dealing with acoustic properties of the walls and floor of a railway passenger coach investigated by means of the experimental analysis of noise produced during train runs and corresponding simulations. In the research, conditions and theoretical approaches for possible reconstructions of walls and floor of the railway passenger coach using new fibrous-microstructure acoustic materials were defined, with the aim of increasing the sound reduction index. The properties of the proposed materials were compared in terms of the acoustic energy transfer through the porous microstructure calculated by means of simulations. The final acoustic effects of different solutions for the incorporation of the materials in the floor structure and in the complete body of the rail passenger coach were evaluated. In this paper the effects on interior noise of the introduction of a new material for floor and wall are presented.

A wheel/rail profile wear is a factor that affects the behavior of railway vehicles such as riding comfort, running stability, running safety and maintenance schedule. To predict wheel/rail profile wear theoretically with dynamic model of the vehicle-track systems, wear coefficient is necessary and these parameters are generally gained from laboratory test such as twin disk test. It is difficult to gain wear coefficient accurately from field data, because the wheel/rail contact conditions which decisive for wear have big variations. On the other hand, there are railway systems in which vehicles of the same type run on the dedicated track with the same operation pattern. In this case, there is possibility to generalize wear coefficient. In this study, we focus on this point, a large amount of wheel profiles from Tokaido Shinkansen, one of high-speed trains in Japan, was investigated. In this paper, wheel wear characteristics of coupled motion is pointed out and these wear characteristics are attempted to demonstrate from a view point of vehicle dynamics.

The control of the imbalance of wheel load in a railway vehicle is important in maintaining running safety against a flange climb derailment. This paper discusses a control method for quasi-static wheel load variation in transition curves by utilizing the leveling devices that are widely installed on recent railway vehicles with air suspentions. We propose a hardware construction to control wheel load variation by using pneumatically controllable leveling valve rod, of which the length is adjustable by using pneumatic cylinders. We also propose an in-vehicle control method, which means that the control method does not depend on the relative position between the vehicle and the earth (e.g. GPS) explicitly. We confirmed that 30% of wheel load inbalance is reduced at its maximum by appling the proposed control method in a transition curve through a running test by the use of a real railway vehicle.

If bearings for gear units of railway vehicles are damaged by seizing, parts of the bearings come off and damage the gear and the gear box, which may lead to the leakage of the gear oil and the defective rotation of the wheel sets. Tapered roller bearings are mostly used in the gear units in Japan. The sliding speeds at the contact surface between the roller end and the inner ring flange of the pinion bearings are higher than that of the gear bearings. In the pinion bearings, therefore, seizure may occur by metal-to-metal contact from inadequate lubrication between the roller end and the inner ring flange. In order to prevent seizure of the bearings and to improve the reliability of the gear units, it is important to clarify the causes of the inadequate lubrication and the mechanism developing from inadequate lubrication into seizure of the bearings. In this work, the effects of bearing rotational speeds and loads, gear oil temperatures and flow rates, and endplay (internal clearance of bearings) values on the performance of the bearings have been investigated by using a rotation testing apparatus for pinion bearings. As a result, it has been clarified that the heating value from bearings increase as the oil temperature decreases and as the oil flow rate increases. In addition, it has been found that the endplay value is greatly reduced when the rotational speed of the bearing rapidly accelerates to high speed under conditions where the temperature of the gear oil is relatively low.

This paper describes a methodology for probability estimation of derailment occurrence due to an earthquake by the use of seismic waveforms. Under the method proposed, an index for probability estimation of derailment is calculated using the estimated or measured seismic waveform of a track and the three types of running safety limit of the target railway vehicle to sinusoidal vibrations of tracks. The index is calibrated using dynamic simulations of the vehicle behavior with various seismic vibrations in order to obtain the relation between the value of the index and the derailment probability. The dynamic simulations can be executed previously. Therefore, when the seismic vibration of the track is obtained, the time to estimate probability of derailment using the method proposed is much shorter than using dynamic simulation of vehicle behavior. In the case of the Sinkansen train dealt with in the design standard of railway structures, if the calculated index is equal to 10, it means that the probability of derailment occurrence is about 50 %. If the index is larger than 30, the train running on the seismically vibrating track certainly derails due to the earthquake. The method is applicable to the following cases; (a) Quick extraction of sections with high probability of derailment occurrence from the whole train line, and support for the restoration of derailments in the event of a large earthquake. (b) Quantitative check of the effect of seismic countermeasures taken of the railway vehicles, tracks and structures from the standpoint of derailment occurrence probability.

In this study, the mechanical properties of the air spring used in secondary suspension systems in railway vehicles have been experimentally determined. Firstly, rubber recipes with different components were determined for the production of rubber material, the main raw material of the air spring. Afterward, the mechanical properties of the elastomer material to be used in the manufacture of the air spring were determined by uniaxial tensile tests and RPA (rubber process analyzer) tests were applied to the samples obtained from different types of rubber compound. The machines used for the production of air spring and the test machines used for determining the mechanical properties of the air springs were specially produced and commissioned within the scope of the study. Blasting, airtightness, lifting–expansion, vertical spring coefficient, horizontal spring coefficient and lifetime tests were carried out by using these test machines. [ABSTRACT FROM AUTHOR]

When a railway vehicle runs on a curved section, wear of wheels and rails occur. This is due to the attack angle of the wheel on the rails that occurs because the steering function of the bogie is insufficient. To overcome these problems, we developed an active steering bogie equipped with an electro-mechanical type of active steering system. The prototype of active steering bogie was manufactured and installed on a test train that operated in sections with many curved sections. Steering performance tests for the test train were carried out on commercial line as the test line. As a result of the test, the performance of curvature radius estimation of the active steering bogie showed a very good performance, with only 2.4% error compared with the track design value. The performance of steering angle implementation of the passive bogie running on the curved section is very poor, but that of the active steering bogie is very good. And the lateral force of the wheel, which is directly related to the wheel wear when running on the curved section, showed a maximum 88.1% reduction of the lateral force. Therefore, considering the test results of the active steering bogie in the test line, the steering performance of the active steering bogie developed for reducing the wheel and rail wear is evaluated to be very good. And the wear of wheel measured after test run was 0.54 mm flange wear in passive bogie, but flange wear was not occurred in active steering bogie. [ABSTRACT FROM AUTHOR]

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Im Projekt „Next Generation Train" (NGT) bündelt das Deutsche Zentrum für Luft- und Raumfahrt (DLR) seine Schienenfahrzeugforschung. Der NGT ist ein Konzept für einen energieeffizienten Ultrahochgeschwindigkeitszug mit Einzelrad-Einzelfahrwerken. Diese erfordern eine Regelung der Lateraldynamik, um eine Spurführung mit reduziertem Verschleiß zu ermöglichen. Auf offener Strecke ist die direkte Messung der Querverschiebung schwer zu realisieren. Dieser Beitrag zeigt auf, mit welcher Sensorkonfiguration es möglich ist, die laterale Position durch einen nichtlinearen Beobachter schätzen zu können. Auf Grundlage der nichtlinearen Bewegungsgleichung und ausgewählter Sensorkonfigurationen wird die Beobachtbarkeit analysiert. Abschließend werden ein Extended und ein Unscented Kalman-Filter für die drei Sensorkonfiguration auf einem Echtzeitsystem implementiert und validiert. In the long-term project "Next Generation Train" (NGT) the German Aerospace Center (DLR) concentrates its railway research. The NGT is an energy efficient high speed train concept using independently rotating wheels. This configuration requires an advanced control of the lateral dynamics to enable track guidance and wear reduction. However, the direct measurement of the lateral wheel-pair position is difficult in a practical environment. This article deals with the question which sensor configuration enables an appropriate estimation of the lateral displacement with a nonlinear observer. Therefore, an observability analysis of the nonlinear system in combination with different sensor configurations is carried out. Finally, an Extended and an Unscented Kalman Filter are implemented and validated on a real-time environment. [ABSTRACT FROM AUTHOR]

Purpose: Primary and secondary suspensions are essential in railway vehicles. In this study, the specifications of suspension components were discussed in detail by referring to the component procurement documents to ensure satisfactory ride quality. Methods: These specifications were compared with those obtained from simulations and measurements of an operational railway system through a transverse vehicle model using the equations of motion derived from the Lagrange equation. The equivalent rail stiffness and damping were also derived. Results: Results showed that the stiffness should be altered according to the vehicle's load, i.e., the number of passengers on board. The secondary suspension stiffness could be determined based on the specification. The primary suspension stiffness was 26% higher than the upper limit of the specification with a load of full-seated passengers. Conclusions: According to the maintenance instructions, a 7-Hz low-pass filter (LPF) was used for car body vibration measurements. It is suggested that the cutoff frequency of the LPF had to be increased to 9 Hz at least for suspension defect diagnoses. Furthermore, a smartphone with a gravity sensor could also be used for measuring car body vibrations. A sampling rate of 100 Hz could obtain the desired results, which could be an effective and efficient method for vibration analyses. [ABSTRACT FROM AUTHOR]

Highlights • Modal Damping Abnormal Variation (MDAV) phenomenon in four-wheeled vehicle. • Continuous modal tracking method. • Continuous modal tracking of four-wheeled vehicle & typical railway vehicle. • Modal shear interchange mechanism & veering behavior of frequency curves. • MDAV occurrence criterion. Abstract The wheel-rail contact intrinsic features aggravate the heavy-duty modal damping conditions of railway vehicle systems under velocity parametric excitation. Therefore, railway vehicles occasionally encounter with modal damping abnormal variation (MDAV), which seriously deteriorates their operation safety and riding comfort. To study the MDAV phenomenon of vehicle system under velocity parametric excitation, a continuous modal tracking method based on the Lagrange cubic spline interpolation is proposed. Utilizing this method, the MDAV phenomenon in four-wheeled vehicle bogie and typical railway vehicle is studied, then the MDAV occurrence criterion is proposed based on the modal shape similarity. It is found that the root causes of MDAV phenomenon is not related to the framework or car body resonance instability resulting from the intersection of wheelset and framework or car body modal frequency curves under velocity parametric excitation, but the modal shear interchange between wheelset mode and that of framework or car body, with the veering behavior of frequency curves. Also, the MDAV occurrence is quite effectively predicted by the proposed criterion based on the modal shape similarity. [ABSTRACT FROM AUTHOR]

Nowadays, rail transport is a very important part of the transportation network for any countries. The demand for high operational speed makes hunting a very common instability problem in railway vehicles. Hunting leads to discomfort and causes physical damage to carriage components, such as wheels, rails, etc. The causes of instability and derailment should be identified and eliminated at the designing stage of a train to ensure its safe operation. In most of the earlier studies on hunting behaviour, a simplified model with a lower degree of freedom were considered, which resulted in incorrect results in some instances. In this study, a complete bond graph model of a railway vehicle with 31 degrees of freedom is presented to determine the response of a high-speed railway vehicle. For this purpose, two wheel–rail contacts grounded on a flange contact and Kalker's linear creep theory are implemented. The model is simulated to observe the effects of suspension elements on the vehicle's critical hunting velocity. It is observed that the critical hunting speed is extremely sensitive to the primary longitudinal and lateral springs. Other primary and secondary springs and dampers also affect the critical speed to some extent. However, the critical hunting velocity is insensitive to vertical suspension elements for both the primary and secondary suspensions. Also, the critical speed is found to be inversely related to the conicity of the wheel. [ABSTRACT FROM AUTHOR]

Integrating new candidate sensors, such as Global Navigation Satellite System (GNSS) and inertial measurement unit (IMU), into fail-safe train positioning systems have recently become a prominent area of research. Although there are a number of contributions related to the design of data fusion algorithms, the lack of details in raw measurements analysis has directly motivated this paper. This paper aims to record data from a variety of sensors (such as GNSS, IMU, magnetometer, barometer, tachometers, and Doppler radars) to evaluate train velocity and railway features (track slope, curve cant, and radius) extending previous works in the instrumentation and measurement field. The field test designed and concisely described in this paper presents several challenging environments, such as a tunnel, which can be used to analyze the candidate sensors limitations. In addition, a demonstration of a data fusion algorithm is presented to calculate train velocity based on measurements from the candidate sensors. The results obtained by an extended Kalman filter using GNSS and IMU are compared with velocity recorded by tachometers and Doppler radars, which is considered to be the reference value. The calculated velocity by IMU and GNSS when both sensors measurements are available presents an absolute error in velocity lower than 2 km/h in more than 90% of test duration. Finally, railway features (curve radius, cant, and slope) are calculated and analyzed according to train and railway dynamics. [ABSTRACT FROM AUTHOR]

Nowadays, the condition-based maintenance is associated more and more with railway transport to improve the safety, availability, reliability and capacity of this transport system, and to reduce life cycle costs for the railway vehicles. The condition-based maintenance requires that vehicle components are replaced based on their real condition, which implies the fault detection and isolation during the train's operation. The paper proposes a method to detect the failure of the damper in the primary suspension of the rail vehicle, based on the analysis of cross-correlation of the vertical accelerations measured on the bogie frame against the two axles. The numerical simulations and experimental results show a very good correlation between the bogie accelerations when the dampers are in a normal operation condition. This thing is shown based on the values of the cross-correlation coefficient (CCC) of the bogie accelerations. The failure in a damper can be detected by the decrease of the CCC of the bogie accelerations, a confirmed fact in the results derived from numerical simulations. The proposed method has more advantages, namely, it is a signal-based method and hence does not require a complex mathematical modelling of the vehicle-track system and knowledge of its parameters or of the external conditions; the method makes relative comparisons between measurements and hence reduces the effect of the factors that influence outputs; the method can be also extended for the secondary suspension; the method can be easily implemented on any type of bogie. [ABSTRACT FROM AUTHOR]

This paper focuses on revealing the dynamic behaviour of a hydraulic yaw damper under very small excitation conditions. First, the measured yaw damper movement is presented when a train experiences unstable motions. It shows that the yaw damper is characterized by very small harmonic movement between 0.5 and 2 mm. Following this, a simplified physical model of the yaw damper is developed which has the ability to reproduce its dynamic performance in the range of operating conditions, and then suitably validated with experimental results. At last, the dynamic behaviour of the yaw damper under very small amplitudes is investigated by comparing with its static behaviour, and the dynamic stiffness and damping in terms of key parameters are studied. It is concluded that there is a great difference in the damper performance between dynamic and static conditions which is caused by the internal damper flexibility under small amplitudes. The percentage of entrapped air in oil, rubber attachment stiffness, and leakage flow have a great effect on the dynamic behaviour of the yaw damper related to the dynamic stiffness and damping. The effect is even more remarkable for smaller amplitudes regarding the dissolved air in oil. Oil leakage has a greater impact on dynamic damping than dynamic stiffness. The series stiffness of the yaw damper is mainly provided by the spring effect of the oil when the rubber attachment stiffness reached a certain limit, and an additional increase in rubber attachment stiffness becomes useless to further enhance the overall stiffness of the damper. [ABSTRACT FROM AUTHOR]

To study the impact of suspended equipment on the ride comfort in a railway vehicle, a rigid flexible general model of such a vehicle is required. The numerical simulations is based on two different models, derived from the general model of the vehicle, namely a reference model of a vehicle with no equipment, and another model with six suspended elements of equipment mounted in various positions along the carbody. The objective of this paper arises from the observation that the literature does not contain any study that highlights the change in the ride comfort resulting exclusively due to the influence of equipment. The influence of the suspended equipment on the ride comfort is determined by comparing the ride comfort indices calculated in the carbody reference points, at the centre and above the two bogies, for a model with six elements of equipment and a model of the vehicle with no equipment. [ABSTRACT FROM AUTHOR]

This paper shows for the first time an approach to harmonise and unify various railway standards into a single method for small object strike against rail vehicles. Emerging composite materials applications for structural parts of railway vehicles highlight the need for assessment of impact response. The objective of this work is to provide a practical and cost-effective approach for rail vehicle car bodies affected by object strikes such as flying ballast, which is a concern and restricting phenomenon for high speed rail operation. A static destructive test method combined with numerical models has been developed. High velocity impact (HVI) simulations are performed with E-glass/polyester laminates based on experiments and similarities between the two cases are highlighted. Validated numerical models are used to simulate three railway standards that are relevant to object strike in order to unify them into the proposed single method. The analysis of the energy transfer characteristics, contact forces, and impact velocity change of the projectile showed that the proposed method can be used alone instead of various existing standards, providing a significant decrease in sample size as well as avoiding the costly high-velocity impact experiments, hence resulting in substantial cost savings. [ABSTRACT FROM AUTHOR]

An active steering system was developed to solve problems such as severe wheel, rail wear, noise and dust generation due to insufficient steering performance of EMU running on an urban railroad section with a large number of curved sections. An electromechanical type active steering system for EMU was designed and a prototype was manufactured. As a result of the performance test of the components for the active steering system, the target design specification was satisfied. Prior to the performance test with test vehicle equipped with the active steering system on test track, the steering control test simulating real track running was conducted, excellent steering performance was noted. The thrust force of the driving unit was also shown to be below the maximum thrust force of the prototype throughout most parts of the track. These results confirm that the simulation test can predict the feasibility of the steering control on the test track for the active steering test vehicle through this simulation test. [ABSTRACT FROM AUTHOR]

This study aims to provide a process for the development of a train collision model that can evaluate the performance of buffers in the coupling system of railway vehicles. The model development process is completed by testing the buffer systems, analyzing the test results, and generating empirical models based on the analyzed results. In the analysis, it is shown that the behavior of the rubber buffer and the high-capacity buffer is well reproduced by the empirical models. A simulation model developed from the process is not only able to produce response behaviors of the buffers that are close to the test results, but is also able to estimate the maximum energy within a 2% error for the rubber buffer and a 4% error for the high-capacity buffer. The validated model can be used in extended systems – when multiple trains are connected through buffer systems – to evaluate the applied force or the absorbed energy on buffer systems, to optimize the configuration of the coupling systems or to evaluate the performance of the buffers under different collision conditions. [ABSTRACT FROM AUTHOR]

The regenerative braking of railway vehicles is widely used in DC railway systems all over the world. This mode of operation provides an opportunity to reuse part of the energy consumed by vehicles, and makes the railway system more energy efficient. During regenerative braking, not only energy management is an issue, but also Electromagnetic Compatibility EMC issues, such as interference of generated current harmonics with a railway signaling system. In this paper, the selective harmonic elimination modulation technique (SHE-PWM) was introduced to the traction drive with a three-level inverter to reduce specific catenary current harmonics generated during regenerative braking. The simulation model of a traction drive appropriate for harmonics analysis was proposed and verified by the measurements in the low-power laboratory drive system. The model was re-scaled to the 3 kV DC system for further study. The model of an induction motor with electromotive force and the method of its calculation was proposed. Furthermore, an analysis of the braking chopper operation was carried out. The asymmetric control of braking chopper was proposed to reduce the current harmonics below limits during chopper operation.

The theoretical research on means to reduce the vertical vibrations and improve the ride comfort of the railway vehicle relies on a mechanical model obtained from the simplified representation of the vehicle, while considering the important factors and elements affecting the vibration behaviour of the carbody. One of these elements is the anti-yaw damper, mounted longitudinally, between the bogie and the vehicle carbody. The anti-yaw damper reduces the lateral vibrations and inhibits the yaw motion of the vehicle, a reason for which this element is not usually introduced in the vehicle model when studying the vertical vibrations. Nevertheless, due to the position of the clamping points of the anti-yaw damper onto the carbody and the bogie, the damping force is generated not only in the yawing direction but also in the vertical and longitudinal directions. These forces act upon the vehicle carbody, impacting its vertical vibration behaviour. The paper analyzes the effect of the anti-winding damper on the vertical vibrations of the railway vehicle carbody and the ride comfort, based on the results derived from the numerical simulations. They highlight the influence of the damping, stiffness and the damper mounting angle on the power spectral density of the carbody vertical acceleration and the ride comfort index.

• Additive manufacture is a potential technology for advanced railway components. • Internal defect is a critical issue to assess the fatigue resistance. • Damage tolerance is urgent for the additively manufacture metal components. Additive manufacturing (AM) is being increasingly applied in aerospace, healthcare, automotive, and energy fields. Despite good design flexibility, short lead times, and high material utilization, the application of AM by the railway industry is still on the way to engineering, particularly when compared with those of the aerospace and automotive industries. In addition, the role of various AM components in maintenance, optimizing design and production is not fully understood. To this purpose, the advantages and challenges in the utilization of AM technologies are well summarized, and the fatigue assessment aspects of AM components have been emphasized. Potential design methods to tackle the challenges including the well-recognized structural integrity, and future prospects are discussed in details. The findings are not only beneficial to the development of AM for railway engineering, but also for enabling the lightweight design of metallic components, and improving the performance evaluation and safety inspection strategies. [ABSTRACT FROM AUTHOR]

• A BV-DL method for predicting DWRD is presented. • The real DWRD of a rail vehicle is obtained with the help of 3DCT. • A laser displacement sensor-based method is used to verify the reliability of the 3DCT model. • A traditional image processing method and two DL methods are compared with the methods proposed in this paper. Large displacements between the wheel and rail lead to track damage or even train derailment. Detecting dynamic wheel-rail displacement (DWRD) can provide a technical means for discriminating the operational health status of rail vehicles and formulating active control strategies. In this paper, a new method, which fuses binocular vision (BV) and deep learning (DL), is proposed to detect the DWRD online, the method is abbreviated as BV-DL. First, a binocular camera is used to capture the dynamic wheel-rail contact video online, while two lasers are equipped to focus on the wheel-rail contact region to locate some keypoints in the wheel-rail contact images. Then, an ROI (region of interest) detection network is proposed to recognize the wheel-rail contact region automatically, and a keypoint detection network is proposed to detect the wheel-rail pixel displacement (WRPD). Finally, a 3D coordinate transformation (3DCT) model is built to calculate the wheel-rail world displacement in real-time, i.e., the DWRD between the keypoints. To test the performance of the method, a laser displacement sensor-based method is used to verify the reliability of the 3DCT model. Meanwhile, a traditional image processing method, a MobileNet V3-based method, and a YOLOX-s-based method are introduced to predict the WRPD. Experimental results show that compared with the four methods, the proposed BV-DL method can achieve optimal results in pixel coordinate calculation and 3D coordinate computation. [ABSTRACT FROM AUTHOR]

The equipment mounted on the carbody chassis of the railway vehicles is a critical component of the vehicle in terms of ride comfort. The reason for that is their large mass, able to visibly influence the vibrations mode of the carbody. The paper examines the influence of the equipment upon the mode of vertical vibrations of the carbody in the high-speed vehicles, reached on the basis of the frequency response functions of the acceleration in three carbody reference points - at the centre and above the bogies. These functions are derived from the numerical simulations developed on a rigid-flexible coupled model, with seven degrees of freedom. As a rule, the results herein prove the influence of the equipment mounting mode (rigid or elastic), along with the speed regime, upon the level of vibrations in the carbody reference points, at the resonance frequency of the symmetrical bending mode. Similarly, it is also demonstrated how the equipment mass and the damping degree of the suspension system affect the level of the vibrations in the carbody.

The paper focuses on a nonlinear model to represent the mechanical behaviour of a mix coil spring - rubber used in the secondary suspension of passenger rail vehicles. The principle of the model relies on overlapping of the forces corresponding to three components - the elastic component, the viscous component and the dry friction component. The model has two sources on non-linearity, in the elastic force and the friction force, respectively. The main attributes of the model are made visible by its response to an imposed displacement-type harmonic excitation. The results thus obtained from the applications of numerical simulation show a series of basic properties of the model, namely the dependence on amplitude and the excitation frequency of the model response, as well as of its stiffness and damping.