Train Suspension Research Articles

Study on the ride comfort of a high-speed sleeper train

The difference in vibration characteristics between passengers and sleepers on high-speed sleeper train ride comfort was rarely studied. This work proposed a 3D rigid-flexible passenger-sleeper-vehicle-track coupling model. The multi-rigid body dynamic method models the supine passengers and sleepers. The detailed car body FE (finite element) model, which contains the train's suspension equipment, is established. Based on the coupling model, the ride comfort index, calculated based on different standards, is analyzed. The difference in the ride comfort index, evaluated using the acceleration at the sleeper and passenger, is compared. Also, the impact of the car body flexibility and the passenger-sleeper model parameters on the ride comfort of a supine human is studied. Then, the ride comfort of the high-speed sleeper train is analyzed when the train is subject to track irregularities excitation, and aerodynamic force (meeting). The results show that using the acceleration of the sleeper can overestimate the ride comfort of the high-speed sleeper train. The head-, and pelvis-sleeper contact parameters are crucial for high-speed sleeper train ride comfort. The ride comfort of the high-speed sleeper trains decreases sharply when trains meeting and passing the special track section.

A Simulation Approach for Analysis of the Regenerative Potential of High-Speed Train Suspensions

This study primarily investigates the adaptability and performance of hydraulic–electric regenerative dampers for high-speed trains by substituting conventional primary dampers with hydraulic–electric regenerative dampers. The primary objectives are to develop a detailed model of primary suspension regenerative damper (PSRD) energy conversion that incorporates factors such as oil pressure loss, motor efficiency, and overall system efficiency, and to perform a comprehensive comparative analysis of vibration responses, wheel wear, comfort indices, and power generation using an integrated MATLAB and SIMPACK co-simulation platform. The results reveal that at an operational speed of 350 km/h, the dynamic responses of the carbody, bogie, wheelset, and dampers equipped with the proposed PSRD systems closely align with those of conventional primary vertical damper systems. The detailed PSRDs’ hydraulic–mechanical–electrical model effectively captures the subtleties of oil pressure fluctuations and their impacts. The wear distribution and magnitude across the vehicle remain consistent during acceleration, constant, and deceleration speeds, ensuring uniform wear characteristics. Under real-world railway operational conditions, the ride comfort metrics of vehicles fitted with regenerative dampers are comparable to those with conventional primary vertical dampers. Furthermore, each regenerative damper can generate up to 21.72 W of electrical power, achieving a generation efficiency of 45.28%. Finally, a test rig was designed and fabricated to validate the primary suspension regenerative damper (PSRD) model, showing good agreement between predicted and actual damping force and power regeneration, with results indicating a peak damping force of 12.5 kN and approximately 230 W of regenerated power. This research provides a theoretical foundation and experimental validation for implementing power regeneration mechanisms in railway transportation, demonstrating that the hydraulic–mechanical–electrical PSRD model can fulfil the performance criteria of conventional dampers while offering substantial energy harvesting capabilities. This advancement not only enhances energy efficiency but also contributes to the sustainable development of high-speed rail systems.

Integration of bio-inspired limb-like structure damping into motor suspension of high-speed trains to enhance bogie hunting stability

Hunting stability is an important performance criterion in railway vehicles. This study proposes an incorporation of a bio-inspired limb-like structure (LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains (HSTs). Initially, a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests. Subsequently, a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior. The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed. Then, the nonlinear damping of the bio-inspired LLS, which has a positive correlation with the relative displacement, can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system. Furthermore, a comprehensive numerical model of a high-speed train, considering all nonlinearities, is established to investigate the influence of different types of motor suspension. The simulation results are well consistent with the theoretical analysis. The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.

Partial Force Calculation and Structural Strength Analysis of Null-Flux Coil for Superconducting Electrodynamic Suspension Train

Partial Force Calculation and Structural Strength Analysis of Null-Flux Coil for Superconducting Electrodynamic Suspension Train

DETOURS AND DELAYS: NAVIGATING THE PANDEMIC'S IMPACT ON INDIA'S TRANSPORT SECTOR AND TOURISM

The COVID-19 pandemic has had a profound impact on the Indian transport industry, affecting various sectors such as aviation, railways, road transport, and maritime. The nationwide lockdowns and travel restrictions imposed to curb the spread of the virus led to a significant decline in passenger traffic and freight movement, causing severe financial distress to the industry. This almost standstill in the movement of the people severely affected the Indian tourism industry which provides 7 per cent of GDP and 9 per cent of employment by 2019. The aviation sector witnessed a sharp decline in passenger traffic, leading to financial losses for airlines and airports. Many airlines were forced to suspend operations or reduce their workforce to survive. Similarly, the Indian Railways faced challenges due to the suspension of passenger trains, impacting revenue generation. The road transport sector also suffered due to the lockdowns, with restrictions on inter-state and intra-state movement affecting the movement of goods and passengers. The maritime sector faced challenges due to disruptions in global trade and port operations. To mitigate the impact of the pandemic, the Indian government announced various relief measures, including financial assistance, waivers, and restructuring of loans for the transport industry. The government also launched initiatives such as the Vande Bharat Mission to repatriate stranded Indians and the One Nation, One Card scheme for seamless travel across different modes of transport. By recognising the importance of the revival of tourism in India Indian Government announced many sops and reliefs to the tour operators, travel agents and transport organisations. Despite these measures, the road to recovery for the Indian transport industry remains challenging. The industry will need to adapt to the new normal by implementing safety measures, embracing digital technologies, and diversifying its operations to ensure resilience in future crises. KEYWORDS: Covid -19, Road transport, Railways, Civil aviation, Tourism

Sports competition among the Jewish population in Łódź in the years 1945–1949

The liberation of Łódź from German occupation enabled a revival of the Jewish culture, including physical culture. In the years between 1945 and 1949, Jewish people living in the city of Łódź reactivated their sporting movement. Jewish sport in Łódź did not achieve the pre-war level. The main reason was migration and a smaller Jewish population. The development of Jewish sport was adversely affected by lack of sports facilities and equipment and costly renovations of club rooms and sports fields. This resulted in the periodic suspension of sports training. The clubs that were formed: The Jewish Sports Club, Jewish Sports Club “Makabi”, Jewish Chess Club, Jewish Sports Club “Jedność” (“Unity”), Jewish Workers Sports Club “Gwiazda” (“Star”) competed as part of sports associations. The players of the Jewish Chess Club of Łódź were a match for the best in the country and the region. They won the Polish team championship twice (1946, 1947) and the City of Łódź championship (1947). Individually, the most successful player was Isaac Grynfeld, who won the 3rd place in the Polish championship (1946) and was 2-time Polish team champion. Among women, the Polish championship in 1949 was won by Róża Herman, PhD. The changes in Polish sport and the loss of cultural autonomy for Jews led to the dissolution of Jewish sports clubs in 1949. They were incorporated in Union Sports Club “Spójnia Solidarność” in Łódź and blended into the sporting movement created by the communist authorities.

GraphFL: Graph Federated Learning for Fault Localization of Multirailway High-Speed Train Suspension Systems

GraphFL: Graph Federated Learning for Fault Localization of Multirailway High-Speed Train Suspension Systems

Dynamic Characteristics and Protection Strategy for Superconducting Electrodynamic Suspension Train with Quenched Magnet

Dynamic Characteristics and Protection Strategy for Superconducting Electrodynamic Suspension Train with Quenched Magnet

Early fault diagnosis strategy for high-speed train suspension systems based on model-agnostic meta-learning

Early fault diagnosis of suspension systems is essential for the safe operation of high-speed trains. However, neural network-based fault diagnosis methods have two remaining issues: the fault samples are difficult to obtain in practice and the early fault features are too weak to be extracted directly from the raw vibration signals using neural networks. A novel strategy is proposed for early faults diagnosis in suspension systems (i.e. component performance degradation within 20%) by integrating a new sample reconstruction method, a new grouping normalisation method, and model-agnostic meta-learning (MAML) algorithm. First, the 1D raw vibration signals are converted to 2D feature matrices consisting of artificial features using the sample reconstruction method; meanwhile, the grouping normalisation method is used to enhance the early weak fault features in the feature matrices. Second, MAML specialises in few-shot model training for early fault diagnosis, with the feature matrices as the training samples. Finally, the results are compared with those obtained using other current methods. The numerical results show that the proposed strategy yielded excellent performance in the few-shot early faults diagnosis of suspension systems, achieving a maximum accuracy of 94.75%.

Robust predictive compensation control for lateral magnetorheological semi-active suspension of high-speed trains with time delay

ABSTRACT Aiming at reducing the effect of time delay on the control performance of magnetorheological (MR) damper semi-active suspension, a control strategy with strong robustness to time delay is investigated in this study, including the force controller of MR damper, the robust controller and the predictive compensator. The force controller of MR damper is built based on the hyperbolic tangent function; the robust controller is built based on the simplified model of car body lateral vibration and is designed by μ-synthesis method considering the effect of time delay; then the Smith predictive model and the lateral velocity predictor are designed, which form the predictive compensator of semi-active controller to reduce the effect of time delay. To validate the effectiveness of the proposed control strategy, several conventional semi-active controllers are designed as comparative objects. The simulation results show that the proposed semi-active control strategy can maintain good performance when time delay is in the range of 0–100 ms and has better robustness to time delay compared with the conventional control strategy.

Parameter optimization of electromagnetic suspension-type maglev train control system based on multi-objective grey wolf non-dominated sorting hybrid algorithm-Ⅱ hybrid algorithm

This paper presents a novel hybrid algorithm based on CMOGWO-ADNSGA-II to solve the vibration stability problem during the operation of a EMS-type maglev train dynamics model subjected to strong non-linear magnetic buoyancy. The proposed algorithm optimizes the control system parameters of EMS-type maglev train suspensions by combining an improved multi-objective chaotic grey wolf algorithm (CMOGWO) with an improved non-dominated Sorting genetic algorithm-II (ADNSGA-II) to enhance the search capability of the algorithm and ensure population diversity. The efficacy of the algorithm is demonstrated by applying it to the EMS-type maglev train suspension frame control system to find the optimal control parameters. Experimental results show that the system with the optimal parameters applied significantly reduces the suspension gap amplitude and the corresponding standard deviation, as well as the vertical acceleration amplitude and the corresponding standard deviation during operation. The proposed algorithm provides a good solution for EMS-type maglev train suspension vibration control, which can improve its performance and safety.

Study on levitation control performance assessment of maglev train based on minimum entropy

In order to meet the strict requirements of the reliability and safety of the commercial operation of the maglev train, it is necessary to carry out the control performance evaluation of the suspension system. However, at present, variance is often used as the evaluation index of control system. This method cannot get accurate performance evaluation results when the system is affected by non-Gaussian disturbance. Therefore, aiming at the non-Gaussian control performance evaluation of maglev train suspension system, a control performance evaluation method of maglev train suspension system based on minimum entropy is proposed in this paper. In view of the non-Gaussian characteristics in the operation data of maglev train suspension system, this paper introduces the feedback invariant entropy of non-Gaussian system, and then realizes the evaluation and analysis of the control performance of maglev train suspension system based on the minimum entropy criterion. Finally, combined with the evaluation and analysis of the operation data of Changsha medium and low-speed maglev train, this paper verifies the effectiveness and accuracy of the proposed performance evaluation method for the control performance evaluation of maglev train suspension system.

Design and Characterization of a Non-Linear Variable Inerter in Vehicle Suspension System

Inerter is a two-terminal component in suspension system such that the force at the two terminals is directly proportional to the relative acceleration of these two points. Studies have shown that the inerter can provide satisfactory vibration isolation for a number of suspension applications, including train suspension, building suspension and vehicle suspension. In the context of vehicle suspension, the existing passive inerter has been shown to provide benefits to vehicle dynamics performance measures, such as ride comfort and road holding ability. However, a basic passive inerter has fixed characteristic, and hence its potential is limited. This study overcome this limitation by incorporating variable inertia in inerter flywheel, however its non-linear characteristic needs to be determined. The method of achieving variable inertia in inerter flywheel is through introduction of movable masses or sliders attached with springs into inerter flywheel. The change of moment of inertia is caused by position change of sliders due to centrifugal force when the flywheel is rotating. Results showed that the proposed variable inerter exhibits a non-linear force-acceleration relationship with respect to its operating rotational speed. A vehicle suspension system equipped with a variable inerter is also able to further reduce vertical vehicle body acceleration and vehicle’s dynamic tire load when compared with vehicle suspension system without inerter and equipped with a passive inerter, which indirectly relates to a better vehicle ride and handling performance improvements. Hence, it can be proved that the proposed variable inerter is better than a passive inerter and is able to provide better ride comfort and road holding ability to a vehicle.

Design optimization of a stepped HTS magnet for electrodynamic suspension train

High-temperature superconducting (HTS) magnets are promising candidates for transportation and power systems, such as the electrodynamic suspension (EDS) train, ultra-high field magnet and magnetic resonance imaging, because of their large current-carrying capacity and low power loss. The critical current depending on magnetic flux density is an essential factor in assessing the application performance of HTS magnets. As usual, the existing HTS magnet is wound with rectangular cross-section, which results in magnetic field concentration inside winding. In this paper, we propose a novel HTS magnet structure with stepped cross-section to alleviate the magnetic field concentration, and resultantly improve the critical current. From this point, this paper aims to design and optimize a stepped HTS magnet with the critical current maximized. Firstly, the structure design of the stepped HTS magnet is performed with a consideration of the application scenario of EDS train. Then, the critical current of the HTS magnet is estimated with a homogenized self-consistent model. Afterwards, an HTS magnet with stepped cross-section is optimized, fabricated and finally tested. The critical current was experimentally measured to verify the simulation results, followed by the electromagnetic investigations of the stepped HTS magnet in the EDS train.

Refined disturbance observer based prescribed performance fixed-time control of high-speed EMS trains with track irregularities

High-speed Electromagnetic Suspension (EMS) train is continuously impacted by the irregularity of the track, which worsens the levitation performance of the train. In this paper, a composite control scheme for the EMS is proposed to suppress track irregularities by integrating a Refined Disturbance Observer (RDO) and a Prescribed Performance Fixed-Time Controller (PPFTC). The RDO is designed to estimate precisely the track irregularities and lumped disturbances with uncertainties and exogenous disturbances in the suspension system, and reduce input chattering by applying to the disturbance compensation channel. PPFTC is designed to converge the suspension air gap error to equilibrium point with prescribed performance by completing error conversion, and solve the fast dynamic issue of EMS. And the boundary of overshoot and steady-state is limited in the ranged prescribed. A theoretical analysis is conducted on the stability of the proposed control method. Finally, the effectiveness and reasonability of the proposed composite anti-disturbance control scheme is verified by simulation results.

Vertical Resonance Simulation of Superconducting Electrodynamic Suspension Train/Bridge Coupled System

The superconducting electrodynamic suspension (EDS) train, which speed over 600 km/h, has the advantages of a lightweight, large suspension gap (up to 100 mm), stable suspension, etc. Therefore, it is expected to become one main form of the next generation of high-speed and ultra-high-speed manned rail transit. The bridge will vibrate and deform when the train passes through the bridge. And the vibration and deformation of the bridge will affect the dynamic response of the train as well. Therefore, the train and the bridge will form an interaction system. And under a certain running speed, train/bridge coupled resonance will occur, directly affecting the train's safety and comfort. In this paper, the MLX01 superconducting EDS train is taken as the research object, established a 14-DOF dynamic model for vertical and pitching vibration analysis of a superconducting EDS train and established a single-span Euler-Bernoulli simply supported bridge. Nonlinear levitation forces connect the train and bridge subsystem to form a superconducting EDS train/bridge coupled vertical dynamic model. Simulation calculation explores the effects of train speed and bridge damping ratio on the superconducting EDS train/bridge coupled system's vertical resonance response. The results show that the train speed and the bridge's natural frequency are two main factors affecting the vertical resonance of the train/bridge. In train operation, the first resonance speed should be avoided. Increasing the damping ratio of the bridge cannot prevent the train/bridge resonance, but it can weaken the dynamic response of the bridge during resonance, and properly increasing the damping ratio of the bridge is conducive to the stability of train operation.

Comprehensive Model Construction and Simulation for Superconducting Electrodynamic Suspension Train

Comprehensive Model Construction and Simulation for Superconducting Electrodynamic Suspension Train

An energy harvesting shock absorber for powering on-board electrical equipment in freight trains

To realize smart detection and safe operation of freight trains, a continuous and stable energy source is required for electrical equipment on the train. It is a feasible scheme to harvest the vibration energy of train suspension to supply power for on-board electrical equipment. This paper presents an energy-harvesting shock absorber (EHSA) based on the slider-crank mechanism and ratchet-pawl mechanism, which provide a vibration reduction effect and renewable electricity. To determine the damping performance and the power generation performance of EHSA, a dynamic model is established based on MATLAB. According to the tests on the mechanical testing and sensing (MTS) bench, the maximum power generation mechanical efficiency of the EHSA is 67.75%, and the maximum output power of the EHSA is 1.65W. In addition, the charging tests on the MTS bench show that the proposed device is applicable to power on-board electrical equipment on freight trains.

Time-varying nonlinear parameters identification of high-speed train suspension system based on WMA

The parameters identification of suspension components provides a foundation for health assessment of the high-speed train. Considering the time-varying nonlinearity of suspension parameters caused by changing temperature, this work identifies the time-varying nonlinear parameters based on the wavelet multiresolution analysis (WMA) combined with the proposed improved Akaike information criterion (AIC). Firstly, the parameters variation law against time-temperature are fitted based on test data and the vibration responses of a two-degree-of-freedom suspension model are obtained. Secondly, the time-varying nonlinear parameters are expanded into scale coefficients using WMA. Thus, the identification of time-varying nonlinear parameters is transformed into the identification of time-invariant wavelet scale coefficients. Then the improved AIC is utilized to select the optimal basis functions and decomposition scales in noisy environments. The identified parameters vectors are used by the improved AIC as evaluation index of identification model to reduce the effect of noise. Finally, the time-varying nonlinear parameters are reconstructed based on the optimal wavelet scale coefficients. The results show that the time-varying nonlinear stiffness and damping coefficients can be accurately identified based on the WMA combined with the proposed improved AIC.

Magnetic Shielding Design of Onboard Superconducting Magnet for Electrodynamic Suspension Train

The superconducting electrodynamic suspension (EDS) train has been expected to be a promising candidate for the future ultrahigh-speed transportation due to its excellent levitation and guidance stabilities, high lift-to-drag ratio, and being free-of of active control. As a core component of the EDS train, the onboard superconducting magnet (SCM) is usually required to generate a strong magnetic field, however, which may threaten the safety of passengers. Therefore, it is indispensable to design a magnetic shielding for onboard SCM, aiming at minimizing the magnetic field in the coach of the vehicle. In this paper, a three-dimensional (3-D) finite element method (FEM) model for solving the electromagnetic problems of magnetic shielding system is established and validated by experimental results. Prior to global optimization, the effects of thickness, multi-layer and partition structure of shielding plate on the magnetic shielding are discussed primarily. It was found that the thickness has a great impact on the shielding effect, while the influence of multi-layer structure is weak. Moreover, the weight of the magnetic shielding plate can be effectively reduced by partitioning it into several blocks with different thicknesses. Based on the above studies, magnetic shielding plate is finally optimized in consideration of the thickness, multi-layer structure and partition. Consequently, the weight of the magnetic shielding plate can be reduced by 20% compared with the original one.