Train Operating Conditions Research Articles

Experimental investigation of dynamic features and propagation law of ground vibrations induced by a suspended monorail train

This study focuses on experimental investigation of the dynamic features and propagation law of ground vibrations induced by suspended monorail transportation (SMT), which is rarely reported. First, a comprehensive field measurement of suspended monorail train-induced ground vibrations is performed and the acceleration responses at different measurement positions are obtained. Then, the vertical and lateral vibrational responses are elaborately analysed in the time and frequency domains. The dynamic features and transmission laws of the ground vibrations are revealed, and some interesting phenomena are discovered. Finally, an effective signal post-processing method is adopted to furthest reduce signal truncation errors. The 1/3 octave analysis method is adopted for elaborately evaluating both the ground vibration levels with time and frequency division under different train operating conditions. The research results can provide useful guidance for route selection of SMT and numerical model validation.

Mitigation Strategy of Neutral-Point DC for Transformer Caused by Metro Stray Currents

Metro stray currents flowing into neutral-point-grounded transformers can cause serious direct current (DC) bias. Affected by both metro train and urban power grid operations, transformer neutral-point DC caused by metro stray current is complex, dynamic, and time-varying, which changes the DC bias risk level of transformers. Thus, just installing blocking devices (BDs) at transformer neutral points with high instantaneous DC may make it difficult to comprehensively mitigate DC bias and lead to increased BD installation. To solve this, through optimizing BD installation placements, a mitigation method for transformer DC bias is proposed. In the proposed method, the DC bias risk level and BD installation number are included in the constraint and objective functions. To evaluate the risk level of transformer DC bias, four indicators are proposed considering the distribution characteristics of neutral DC. To optimize the BD installation placements, the effects of both the metro train dynamic operation and the operation topology of the urban power grid on neutral DCs are considered. The Monte Carlo method is used to sample the train operation conditions and a relation matrix among transformers is established. Applying the method to a certain power system, the result of BD installation placements shows that the transformers supplying the metro system must have BDs installed at their neutral points.

Train-earth-grid coupling DC magnetic bias model for stray current diffusion

The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation.

Electrical Characterization of Pantograph and Catenary Offline Under Train Operating Conditions Based on Improved Habedank Model and AT Power Supply Network

Electrical Characterization of Pantograph and Catenary Offline Under Train Operating Conditions Based on Improved Habedank Model and AT Power Supply Network

Research on Harmonic Overvoltage of Cable Sheath on 220kV Side of Electric Railway Traction Station

Abstract The special operation mode of high-speed railway will generate a large amount of harmonics. The harmonics will be transmitted to the 220kV side high-voltage cables through the traction transformer, and harmonic voltages will be generated on the cable sheath, threatening the safe operation of the cables. In this paper, on the basis of the measured harmonic data of the traction substation, a harmonic source model based on the measured data is established, which solves the complex problem of harmonic source modeling and can accurately reflect the actual operating conditions of high-speed trains. On this basis, the harmonic voltage characteristics of the cable sheath on the 220kV side of the high-speed railway under the three working conditions of traction, regenerative braking and inertia are simulated and calculated, and the effects of cable length, cable grounding method, and harmonic current parameters on the harmonic voltage are explored. Affect the law. The results show that under different operation modes of high-speed rail, the harmonic voltage of the sheath far exceeds the normal operation of the power frequency, and the maximum value of the harmonic voltage of the cable sheath can reach 454V under the traction condition; Under working conditions, the overvoltage of the metal sheath is greatly affected by the grounding method of the cable, the length of the cable and the harmonic current content. The above research results have important reference significance for the safe operation of electrified railways.

Collaborative Optimization Method for Multi-Train Energy-Saving Control with Urban Rail Transit Based on DRLDA Algorithm

With the traffic congestion problem deteriorating, people increasingly choose urban rail transit (URT) to travel. Although URT alleviates traffic congestion, the long-term operation of a large number of trains leads to huge energy consumption. In order to adapt the major social development concept of “Low carbon”, a multi-train energy-saving control collaborative optimization method is proposed in this paper. First, the composition of single train operating conditions is determined by the conversion of operating conditions between stations and the force changes under the premise of ensuring safe and on-time train operation. A single-train energy consumption calculation combinatorial optimization model with the dual control objectives of reducing passengers’ average waiting time as well as train traction energy consumption is established. The energy saving control strategy of a single train is investigated by ARMA-Radial Basis Function Neural Network (ARMA-RBFNN) and Genetic Algorithm (GA). Next, the queuing theory is introduced to analyze the variation in passenger waiting time for multiple trains at different arrival intervals. A Deep Reinforcement Learning (DRL) algorithm is designed to obtain the correlation among passenger waiting time, arrival interval and train stopping time. The optimization objective is to minimize the multi-train traction energy consumption and the average passenger waiting time while considering conditions such as train operating safety interval, speed limit, multiple operating state and single train energy-saving models, etc. Then, a multi-train cooperative energy-saving control model is proposed based on the Dragonfly Algorithm (DA). Finally, a case study of Beijing Metro Line 4 is conducted to illustrate the effectiveness of the proposed method. The results demonstrate that the total traction energy consumption and passenger waiting time are reduced by 3.1% and 5 s, respectively, compared with the method of independently optimizing the single-train control strategy. The findings can aid in the development of energy-saving strategies and also provide a basis for energy-saving operation control of multiple trains.

In-train particulate matter (PM10 and PM2.5) concentrations: Level, source, composition, mitigation measures and health risk effect – A systematic literature review

Exposure of commuters to pollutants on trains has been an essential topic of discussion in recent years due to its health implications. This review summarizes literature that measures particulate matter (PM) in trains to understand the concentration levels and health effects caused due to exposure. The databases searched were Scopus, Web of Science (WOS) and Google Scholar. Articles, conference papers and textbooks written in English, measuring PM in train carriages and published between 1998 and 2022 were selected for this review. Out of the 3247 articles identified, only 73 were included in this study. 15/20 articles agreed that concentration is significant at the underground segment by a factor of 7 than the counterpart above/ground levels. The review observed that 80% of the publication of in-train concentrations of PM10 and PM2.5 were above the WHO standard. In-train PM2.5 concentration ranges from 2 μgm−3 to 563 μgm−3, and in-train PM10 concentration ranges from 6 μgm−3 to 997 μgm−3. People’s activities, mechanical movement of train parts, train operation conditions and local emissions were the primary source of PM. Future research should focus on health damage due to PM exposure and the effect of the filtration system on PM levels in trains.

Small excitation self-powered sensing energy harvester for rail traffic condition monitoring

A small excitation bistable vibration energy harvester for railway transportation is developed for self-powered condition monitoring utilizing low-frequency vibration of key train components. Analyze operational vibration data collected from trains to determine design requirements. A free sliding magnet is placed in a tube with a top fixed magnet and two limit springs, using gravity, magnetism, and spring force to provide two stable positions for the movable magnet. This structure can enter the bistable operating region under small excitation amplitude and has a wide operating bandwidth. Build and test prototypes using conditions similar to real train operating conditions. A wide operating bandwidth (7 Hz-46 Hz) is obtained due to the bistability. Peak output power is 3.17mW measured into a 900 Ω resistive load at 30 Hz and 1.4g.

Current signal characteristics analysis of transmission system in high-speed train under abnormal vibration conditions

Abnormal vibration monitoring of high-speed trains is usually performed by analysing the vibration acceleration of specific structures to identify characteristic signals. However, due to the harsh operating environment caused by multiple internal and external sources of compound excitation, vibration monitoring of high-speed trains faces numerous problems, such as easy damage to vibration sensors, limited installation space for testing equipment, and difficulty in vibration testing of rotating parts. This paper takes high-speed train transmission system as the research object, combines multi-body system dynamics and electric transmission control theory to establish an electromechanical model of high-speed train transmission system, and carries out simulation research for three typical working conditions of high-speed train, which are wheel flat, wheel polygon and hunting motion. By analysing the transmission response of wheel–track relationship, gearing and motor current under three operating conditions based on Motor Current Signal Analysis (MCSA), it can be concluded that the motor current signal can be used instead of the vibration signal to identify the above three abnormal operating conditions by analysing the characteristic frequencies in the motor stator current. While MCSA is commonly used to diagnose faults such as tooth surface pitting and tooth root cracking inside gearboxes, the results of this paper show that motor current signals can also be used to monitor any abnormal operating conditions of high-speed trains that can cause changes in motor load torque.

Destructive test study of the flexural load capacity of a full-scale reinforced concrete T-girder strengthened by externally prestressed CFRP plates

With the upgrade of the transportation capacity of some existing freight tracks to heavy-haul railways in China, there is increased use of heavy-haul trains with larger axle loads and traction masses than in the past. The existing railway bridges not only bear the increased loads of heavy-haul trains but also experience much more loading times. This situation greatly affects the normal use and even the bearing capacity of reinforced concrete bridges and leads to concrete cracks and decreased flexural rigidity of the girders. As a result, the ultimate bearing capacity and operational safety of girders must be reasonably strengthened. Two reinforced concrete T-girders with a span of 12 m were demolished after 20 years of service. One of the T-girders, without any treatment, was selected for the destructive bending test, and the failure process and actual ultimate bearing capacity were obtained. The other girder was strengthened by the tensioning of prestressed carbon fiber reinforced plastic (CFRP) plates which showed the advantages of high tensile stress more than 2600 MPa, light mass, anti-corrosion and good resistance to durability. Then a destructive comparative bending test was performed to verify the strengthening effect. The research results showed that the actual ultimate flexural load capacity of the unstrengthened T-girder was 1.58 times the original design load capacity. After the T-girder was strengthened by prestressed CFRP plates, the cracking moment and actual ultimate flexural load capacity were 30.5% and 16.4% higher, respectively, which could decrease the cracking degree and deflection-span ratio of the T-girder under the operating conditions of heavy-haul trains. The strengthened T-girder showed a desirable serviceable limit state and ultimate flexural bearing capacity for KM98 trains with 300 kN axles.

Dynamic Performance Analysis, Optimization, and Verification of DC Auto-Transformer System With Rail Potential and Stray Current Emulator

DC auto-transformer (DCAT) traction power supply system has been studied to suppress the rail potential and stray current for urban rail transit (URT), which generally takes the constant train load to simplify the analysis. However, in practice, the train is a non-linear load with frequent accelerating and braking, which leads to the rail potential and stray current changing with the different train operating conditions. Therefore, the dynamic performance analysis and optimization of DCAT system are discussed in this paper. And the rail potential and stray current dynamic emulator (RSDE) for DCAT system verification is proposed because it’s difficult to test DCAT system directly in the actual URT. Based on the configurations and operation principles of both DCAT system and RSDE, the comparisons between DCAT system and the existing system on the rail potential and stray current are discussed. Meanwhile, considering the train dynamic performance, define the dynamic performance index (DPI) to evaluate the effects of DCAT system on the rail potential and stray current mitigation, and optimize DCAT system with DPI. Finally, the correctness and effectiveness of DCAT system on the rail potential and stray current mitigation are validated by simulation results and experimental verification.

Following Consistency of Energy‐Saving Operation for Urban Rail Trains Based on Event Triggering Mechanism

To reduce the traction energy consumption of urban rail trains by regenerating energy, a train traction and braking model was designed based on algebraic graph theory and train dynamics theory and the following consistency model of energy‐saving operation of urban rail trains was constructed based on the conditions of the coordination coefficient and the operating condition conversion of trains. Not only to constantly update the consistency controller and save communication resources but also to optimize the energy‐saving effect, the consistency algorithm of event triggering was used to search for the optimal operating conditions of trains and the energy‐saving operation scheme for multiple trains was established. Taking the train diagram of a subway line in Jinan as an example, the energy‐saving control scheme of four trains was solved by MATLAB simulation. The simulation results show that the model can not only ensure parking accuracy and punctuality but also energy savings effectively; that is, the proportion of the total regenerative energy used by the follower train in the actual energy consumption is increased from 3.32% to 10.76%, and the actual total energy consumption of the train is reduced by 9.23%.

A New Hybrid Ensemble Deep Learning Model for Train Axle Temperature Short Term Forecasting

The axle temperature is an index factor of the train operating conditions. The axle temperature forecasting technology is very meaningful in condition monitoring and fault diagnosis to realize early warning and to prevent accidents. In this study, a data-driven hybrid approach consisting of three steps is utilized for the prediction of locomotive axle temperatures. In stage I, the Complementary empirical mode decomposition (CEEMD) method is applied for preprocessing of datasets. In stage II, the Bi-directional long short-term memory (BILSTM) will be conducted for the prediction of subseries. In stage III, the Particle swarm optimization and gravitational search algorithm (PSOGSA) can optimize and ensemble the weights of the objective function, and combine them to achieve the final forecasting. Each part of the combined structure contributes its functions to achieve better prediction accuracy than single models, the verification processes of which are conducted in the three measured datasets for forecasting experiments. The comparative experiments are chosen to test the performance of the proposed model. A sensitive analysis of the hybrid model is also conducted to test its robustness and stability. The results prove that the proposed model can obtain the best prediction results with fewer errors between the comparative models and effectively represent the changing trend in axle temperature.

ПОВЫШЕНИЕ УСТОЙЧИВОСТИ ДВИЖЕНИЯ ПРИЦЕПНЫХ АВТОТРАНСПОРТНЫХ СРЕДСТВ

Today, automobile and tractor trains with trailers are quite popular vehicles used for transporting agricultural goods in the agro-industrial complex of the Russian Federation. Road trains and trac-tors with trailers are characterized by lower performance indicators (maneuverability, stability of movement) than single vehicles. Accordingly, special requirements for safety and trouble-free op-eration are imposed on motor-tractor trains. The author of the article proposes a technical solution that provides longitudinal stability of the movement of multi-link trackless vehicles, and has, in comparison with known analogues, simplicity of design and increased efficiency in the operating conditions of multi-link tractor trains. Analytical studies have been carried out, which made it possible to justify the rational kinematic and geometric parameters of the proposed technical solu-tion. The strength parameters of the damping device installed at the coupling point of tractors and trailers, and ensuring the operational reliability of trailed dump vehicles, are determined. The re-sults of the conducted research are recommended to both domestic and foreign research institutes, design and production structures of the automotive industry for further study and refinement of the proposed device with a view to its possible introduction into practice.

Blockchain‐enabled balise data security for train control system

The train control system is the railway system's brain, ensuring the train protection and the railway network's operating performance. This control system relies on the balise data received via near-field wireless communication to localize the train and update real-time operating conditions and constraints. The attackers can capture these data through their balise antenna and corrupt them through replay or false data injection attacks. This corrupted data can compromise train safety and jeopardize the entire train fleet operations. To overcome these attacks and to ensure the trustworthiness of balise and data integrity, this study proposes the permissioned blockchain-enabled two novel architectures for data transactions. Besides, each balise is equipped with a novel built-in blockchain cryptography algorithm to create its secret and public keys to provide the key integrity without needing third-party Certification Authority of conventional Public-Key Infrastructure based security systems. Each balise can create the unique signature using a ‘nonce’ signal sent by the train control system in the static architecture or using a self-generated ‘k-once’ secret key per train control system in dynamic architecture. Finally, the case studies are carried out to confirm the security sufficiency of the proposed architectures.

Analysis of Forces in Linear Synchronous Motor With Propulsion, Levitation and Guidance for High-Speed Maglev

Propulsion, levitation, and guidance (PLG) are the key technologies of high-speed maglev system. A linear synchronous motor (LSM) combined with PLG is presented, which can simultaneously realize the three functions of PLG. A novel analytical method for analyzing the 3-D electromagnetic forces of the LSM is proposed. First, the overall structure and operating principle of the high-speed maglev system are discussed. Second, the 3-D analytical model of the LSM is proposed, and the analytical expressions of propulsion force, levitation force, and guidance force are obtained according to the change in the system magnetic field energy during the operation of the maglev train. Finally, the 3-D force characteristics of LSM under different operating conditions of maglev train are calculated and simulated, and the correctness of the 3-D analytical model is verified by the publicly measured data on the Yamanashi line.

Load and response quantification of direct fixation fastening systems for heavy rail transit infrastructure

Ballastless track (i.e. slab track) systems are used extensively in passenger rail applications for improved track stability, alignment control, vibration, and life cycle cost (LCC) benefits. These systems regularly rely on Direct Fixation (DF) fasteners to connect the rail to the structure. Field performance observations have indicated that even under similar track geometry and train operating conditions, the DF fasteners useful life varies widely. Meanwhile, a review of literature reveals that there is limited prior research to guide optimization of DF fastener designs for heavy rail transit. Therefore, researchers at the University of Illinois at Urbana-Champaign (UIUC) conducted a field investigation at three sites on a United States legacy heavy rail transit system to quantify wheel-rail interface loading demands and DF fastener response. Track response variance across similar track geometry was found. Wheel loads ranged between 2.7 to 18.2 kip (12.0 to 81.0 kN) and 0.9 to 12.4 kip (4.0 to 55.2 kN) for vertical and lateral loads, respectively. Lateral rail head displacements ranged between −0.05 to 0.16 inches (−1.27 to 4.06 mm) while dynamic lateral stiffness ranged from 42 to 62 kip/in. (7.3 to 10.8 kN/mm), indicating a low stiffness ratio for the DF fastener studied. Differences in behavior are attributed to dynamic vehicle-track interaction, the relationship between balanced and operating speeds, and differences in track gauge between sites. A comparison of vertical loading results with two additional heavy rail transit agencies shows Burr distributions that accurately represent the loading demands. Results from this study provide quantitative information that can be leveraged to improve heavy rail transit DF fastening system design and development of representative design validation testing protocols.

A Full-Scale Experimental Investigation on Ride Comfort and Rolling Motion of High-Speed Train Equipped With MR Dampers

Achieving higher operation speeds safely and comfortably is yet a significant challenge in the railway industry. The rail irregularities and wheel-rail interactions in a train running at high speeds may result in large-amplitude vibration in the train’s car body and affect passengers by reducing ride comfort. The train suspension systems have a crucial role in reducing the vibration and improving ride comfort to an acceptable level. In this context, an exclusive semi-active magneto-rheological (MR) damper with a favorable dynamic range was designed and fabricated. The MR dampers were installed in a high-speed train’s secondary lateral suspension system in replacement of original passive hydraulic dampers, with intent to mitigate vibration of the car body and keep the ride comfort in a proper level at low and high running speeds. A unique full-scale experimental investigation on the high-speed train equipped with MR dampers was carried out to evaluate the MR damper functionality in a real operating situation. The full-scale roller experiments were conducted in a vast range of speeds from 80 to 350 km/hr. At each speed, different currents were applied to the MR dampers. The car body dynamic responses were collected to evaluate the ride quality of the train. Ride comfort indices under various train operating conditions are calculated through Sperling and UIC513 rules. This study reveals that the designed MR dampers effectively reduce the car body’s rolling motion. According to Sperling ride comfort index, the car body vibration was “clearly noticeable” at some running speeds when adopting the MR dampers, but it was not unpleasant. Besides, a “very good comfort” was achieved according to the UIC513 criterion. Also, no train instability was whatsoever observed at high speeds. This experimental investigation bears out the capability of the devised MR damper to achieve desirable ride comfort under high running speeds.

АНАЛІЗ ВПЛИВУ ПЛАНУ ТА ПОЗДОВЖНЬОГО ПРОФІЛЮ КОЛІЇ НА УМОВИ ЕКСПЛУАТАЦІЇ КОНТРЕЙЛЕРНИХ ПОЇЗДІВ

Summary. In this paper, the influence of the plan and longitudinal profile of the track on the operating conditions of piggyback trains is analyzed. The economic indicators of the organization of piggyback trains in the direction Lviv – Mukachevo are determined and compared with the indicators of road transport on the route between the same cities. An analysis of recent research and publications on the development of piggyback transport shows that further research in this area is necessary and relevant. The experience and practice of piggyback transportation has shown their feasibility and advantages. As you know, container transportation is the transportation of loaded trucks or semi-trailers on special railway platforms. That is, this part of the road meets the basic rules for determining the technical, operational and economic performance of railway transport. It should be noted that on the railways, the indication of the group of indicators, including the cost of transportation, among other factors, is significantly influenced by the plan and profile of the track. Therefore, in this paper, the plan and longitudinal profile of the railway line is presented as a combination of individual real reference sections of the specified direction, within which the piggyback transport is carried out. According to the results of calculations of the volumes of possible cargoes, directions of transportations and terminals where it will be possible to carry out loading and unloading of pigtails, perspective directions of piggyback trains have been established. Histograms of the distribution of slopes and curves in the sections Lviv – Stryi, Stryi – Lavochne, Lavochne – Mukachevo were constructed. The results of traction and operational calculations are given. The train of the established lengths with evenly distributed weight is accepted as calculation model. The settlement train consists of a locomotive, two passenger cars for drivers and forty or twenty long-base platforms loaded with road trains. A system of criteria for the evaluation of direct road and combined (piggyback) transportation is proposed. Two variants of cargo delivery organization between Lviv and Mukachevo are compared: automobile and piggyback. The dependence of the cost of transportation and reduced costs on their range for road and piggyback transportation at a technical speed of 50 km/h. Further scientific research may be aimed at improving the technical component that affects the economic attractiveness of piggyback transport for domestic and foreign indicators. After all, the development of this type of transportation will help strengthen Ukraine's competitive position in the European logistics market.

Анализ загрузки путевого развития станции (по данным архивов систем централизаций стрелок и сигналов)

The development of equipment and technology of train operation, railway automation systems and new methods of train driving open the way for further intensification of train operation, reducing the time spent on standard operation procedures. Virtual coupling allows you to reduce a train-to-train interval. Automated schedules of the executed movement record performance of train operation, automate the formation of a train-dispatcher’s reports and delivery of orders to station attendants, allow timely detection of the causes of train delays and take appropriate measures. The points of growth in traffic intensity and volume could be in enhancing the level of intelligence of automation and telemechanics systems. Modern dispatch and electrical centralized systems contain archiving subsystems that store prompt train operation conditions and operator orders. But such data is used only when analyzing emergency situations - there is no systematic analysis of archive information to find hidden patterns and extract knowledge useful for optimizing the transportation process. In this paper, we propose a method for estimating the current train operation load of a railway station, and provide relative criteria for evaluating the actual load and algorithms for determining their numerical values. The analysis of the time series of the proposed criteria obtained for a single station equipped with a relay-processor centralized system is carried out. The analysis indicated a weekly cycle of train operation load of a station with good repeatability. The fact of reducing the speed of trains before the input signal in the through-pass routes with a preset route was revealed. Smoothing out the identified irregularities can positively affect the carrying capacity of a railway section as a whole.