Maglev Train Research Articles

On the active flow control in maglev train safety under crosswinds: Analysis of leeward suction and blowing action

On the active flow control in maglev train safety under crosswinds: Analysis of leeward suction and blowing action

A Modified ADRC Scheme Based on Model Information for Maglev Train

During the operation of maglev trains, they are subjected to various disturbances. The presence of these disturbances presents a significant challenge for attaining high-performance control and even poses the risk of system instability. To further enhance the anti-disturbance capability of maglev trains, this paper proposes a model information-assisted modified active disturbance rejection control (MADRC) approach. A mathematical model of the single-point suspension system of maglev trains is constructed for the design of the extended state observer (ESO), which is a modified extended state observer (MESO), and a nonlinear mechanism is incorporated to boost the performance of the ESO. Owing to the introduction of model information, the estimated quantity of disturbances by MESO no longer considers the system model deviation as a disturbance. Hence, the linear feedback control law is modified accordingly. The MESO is regarded as an ESO with time-varying gain using the equivalent gain method, and its stability is proven using the Lyapunov method. The tracking and anti-disturbance performances of different controllers are compared via simulation experiments. Suspension and anti-disturbance experiments are conducted on the single-point suspension experimental platform, verifying that the proposed MADRC has a more potent suppression ability for load disturbances in the suspension system.

Development of mechanical properties of concrete in vacuum tunnel of vacuum-based maglev train

The vacuum-based maglev train is an emerging transportation system currently under development worldwide. While concrete is a technically viable material for constructing vacuum tunnels, its mechanical performance in this unique environment remains unclear. This paper investigates the behavior of concrete in vacuum using a large customized vacuum tube. The results show that concrete undergoes significant water loss in vacuum, resulting in impeded cement hydration and porous hydration products with a foam structure. Vacuum exposure during the early ages of concrete has negative effects on mechanical properties. However, once the cement hydration reaches a high level of maturity, further vacuum exposure has little influence. Compared with atmospheric conditions, the shrinkage of concrete in vacuum is significantly increased. These findings provide a valuable experimental database and new insights for the use of concrete in vacuum-based maglev trains.

A Fast Multi-Objective Optimization Method for Control Parameters of High-Speed Maglev Vehicle-Bridge System

A fast multi-objective optimization method (FMOOM) is proposed by optimizing control parameters to improve the dynamic performance of a high-speed maglev vehicle–bridge system. This approach involves generating the corresponding dynamic response to the sampled control parameters using a theoretical model of a high-speed maglev vehicle–bridge system, followed by establishing an adaptive surrogate model for the relationship between the control parameters and the dynamic response extrema. In the second step, we combine the adaptive surrogate model and the multi-objective gradient-based optimizer (MOGBO) algorithm to obtain the Pareto solution set satisfying different performance indexes. Additionally, the control parameters are optimized using the fuzzy comprehensive evaluation method. In the numerical simulation, we investigate five maglev trains and ten-span simply supported beam bridges and the theoretical model is verified by comparing the calculations with the measured results. The optimization effect of FMOOM is analyzed under different working conditions. The results show that the adaptive surrogate model has good prediction accuracy based on the radial basis function. Furthermore, the Pareto solution distribution of different schemes using FMOOM is reasonable, and the optimization results are as expected. Compared with the reference scheme, the dynamic response of the maglev vehicle–bridge system is smaller after being subjected to FMOOM optimization, and the six performance indexes are dramatically improved.

A Data-Driven Comprehensive Evaluation Method for Electromagnetic Suspension Maglev Control System

As new advanced vehicles, the safety and stability of electromagnetic suspension maglev trains have always been a subject of concern. This study introduces the improved R index and τ-distance index into the performance evaluation of the suspension control system, respectively assessing the stability of the suspension gap and the smoothness of train operation, combining them with grey relational analysis to achieve data-driven comprehensive evaluation. Furthermore, feasibility tests on the Fenghuang Maglev Express validate the effectiveness and superiority of the comprehensive evaluation method based on measured data. Experimental results demonstrate that the data-driven comprehensive evaluation method, through designing specialized evaluation metrics and increasing assessment dimensions, effectively evaluates the performance of the suspension system control loop. Compared to a traditional error integral comprehensive performance index, it offers greater comprehensiveness and accuracy, along with real-time state-monitoring capabilities.

Review of Fault-Tolerant Control Methods for Suspension Systems: From Road Vehicles to Maglev Trains

Review of Fault-Tolerant Control Methods for Suspension Systems: From Road Vehicles to Maglev Trains

Stochastic optimization of levitation control system for maglev vehicles subjected to random guideway irregularity

The dynamic performance of maglev vehicle-bridge coupled systems subjected to random guideway irregularity, especially the levitation stability of the running vehicle subsystem, is a critical issue affecting the safe operation and the comfort riding of maglev railways. This study is devoted to stochastic optimization of the levitation control system considering the coupled vibration of maglev vehicle and bridge under the random guideway irregularity. To alleviate the computational burden in the stochastic optimization process, the explicit expressions of the critical responses of the maglev vehicle-bridge coupled systems and the sensitivities of critical responses with respect to the feedback gains of the proportional-integral-derivative (PID) levitation controller are respectively constructed in terms of the guideway irregularity by virtue of the dimension-reduced formulation capability of the explicit time-domain method (ETDM), enabling stochastic dynamic analysis and stochastic sensitivity analysis to be executed at high efficiency. The stochastic optimization problem is formulated as the minimization of the standard deviation of the air gap variation with the constraint on the standard deviation of the current variation, and the optimal values of the PID gains are searched by the gradient-based method of moving asymptotes (MMA), in which the statistical moments and moment sensitivities of the critical responses required in the optimization process are obtained by ETDM. A numerical example with a 2-degree-of-freedom maglev vehicle moving on a multi-span simply-supported bridge is used to demonstrate the efficacy of ETDM for the stochastic analysis of maglev vehicle-bridge coupled systems under guideway irregularity. An engineering example involving a 3-car maglev train traversing a multi-span simply-supported bridge is further presented to show the effectiveness of the ETDM-based approach for the stochastic optimization of large-scale engineering problems. The levitation stability of the maglev train under the action of random guideway irregularity is considerably improved with the use of optimal feedback gains.

Research on Vibration Control Regarding Mechanical Coupling for Maglev Trains with Experimental Verification

The electromagnet module, as a fundamental component providing levitation force for maglev trains, plays a crucial role in ensuring the stability of train operation. However, vibrations can easily occur due to the mechanical coupling between the two suspension points of the electromagnet module. To reveal the inherent instability of the system and the coupling relationship between the state variables, a state-space equation that considers the mechanical coupling between the two suspension points is established. Furthermore, a differential control algorithm based on geometric feature transformation is proposed to mitigate the structural coupling vibration. Simulation experiments are conducted to compare the dynamic characteristics of the system before and after implementing the improvement algorithm under complex conditions. At the same time, the influence of control parameters on electromagnetic vibration was analyzed, focusing particularly on vibrations resulting from parameter mismatch, offering crucial insights for enhancing system stability. Additionally, suspension tests are carried out on the high-speed double bogie test platform in the Key Laboratory of Hunan Province to further validate the effectiveness of the proposed algorithm. The proposed control framework is both effective and concise, making it easy to implement in engineering applications. This research holds significant practical value in improving the stability of maglev trains.

Thermodynamic properties of [formula omitted] double quantum wire in the presence of impurity and Rashba spin-orbit interaction

We investigate the effects of impurities and Rashba spin-orbit interaction on the thermodynamic properties in the InxGa1−xN double quantum wire. The energy and eigenvectors of our system are obtained through analytical diagonalization in the presence of external fields, Rashba spin-orbit interaction, and impurities. These energy levels are used to analyse the entropy, mean energy, heat capacity, and free energy of the InxGa1−xN double quantum wire. The system's entropy increases with temperature and Rashba spin-orbit interaction but decreases with impurity. At low temperatures, entropy appears weakly dependent on impurity and exhibits minimal dependence on it. The heat capacity shows a peak structure and rises as impurity and the Rashba spin-orbit interaction increase at low temperatures. At low temperatures, the system's mean energy gradually increases. As the temperature rises, the mean energy becomes independent of interaction strength and increases more rapidly. The mean energy decreases with increasing impurity and Rashba spin-orbit interaction. The thermodynamic properties of our system, such as entropy, heat capacity, mean energy, and free energy, make it suitable for applications in electronics (such as the fabrication of energy storage devices and transistors), industry (such as the operation of magnetic levitation trains), and medicine (such as MRI).

Optimization of Nd-Fe-B permanent magnet guideways with high-temperature stability

High-temperature superconducting (HTS) pinning Maglev systems are advantageous due to their ability to achieve large-scale passive-stabilized levitation. Elevated temperatures can lead to a reduction in the magnetic characteristics of the permanent magnet guideway (PMG), which may pose a risk to the safe functioning of HTS Maglev trains. In order to guarantee the secure and dependable functioning of HTS Maglev trains, it is necessary to augment the high-temperature stability of the PMG. This study involves simulating the high-temperature stability of present PMGs and developing a new PMG that exhibits greater performance. Magnetic field simulation is employed to compute the demagnetization of permanent magnets (PMs) in several typical PMGs, encompassing both reversible and irreversible scenarios, in order to examine the factors contributing to demagnetization and evaluate the thermal stability of the PMGs at elevated temperatures. The grade, size, and magnetization direction of the Halbach-type PMG are subsequently optimized and compared to the original Halbach-type PMG. Following this, ideas for further optimization are provided. The optimized Halbach-type PMG reduces the overall decay ratio of the highest magnetic flux density Bz by 5.77% compared to the existing Halbach-type PMG. Additionally, the irreversible decay ratio is decreased by 6.13% at 85 ℃. The levitation force decay ratio on the HTS bulks above the optimized Halbach-type PMG is decreased by 8.11% compared to the existing Halbach-type PMG. Additionally, the irreversible decay ratio is reduced by 9% at 85 ℃. This study provides valuable insights for enhancing the efficiency and performance of PMGs and HTS Maglev trains over extended periods of operation.

Method of field measurement of electromagnetic environment of high speed maglev train

Abstract In order to reduce the complexity of the magnetic field test of maglev trains and improve the accuracy of measurement data, this paper proposes a field measurement method of maglev train radiation emission based on high-speed parallel adaptive filter denoising technology. This measurement method is not limited by special measurement sites, and has the characteristics of high-speed measurement, real-time data processing, and large-capacity data storage. It breaks through the technical bottleneck of the traditional measurement system. The electromagnetic radiation emission of high-speed maglev trains is measured in real-time through multi-antenna synchronous measurement technology, and multi-channel high-speed RF signal measurement and acquisition of external signals are further carried out by blind source separation technology, environmental pre-scanning is carried out, environmental interference characteristics are obtained through feature statistics, and the radiation signal to be measured is estimated by blind source separation algorithm. It helps to achieve the purpose of accurately measuring the electromagnetic radiation emission of high-speed maglev trains. Through field testing, the denoising performance of the method reached 20 dB. Through field testing, the denoising performance of the method reached 20 dB.

Research on control parameters of high-speed maglev train under stochastic track irregularities

During operational phases, maglev trains encounter track irregularities, presenting a formidable challenge to the integrity of their control systems owing to the inherently stochastic nature, a challenge accentuated in the context of high-speed maglev trains. This study aims to comprehensively examine control parameters within the context of stochastic excitation resulting from track irregularities. Through the development of a rigorous stochastic response analysis model utilizing the pseudo excitation method, the investigation delves into the dynamics of an EMS-type high-speed maglev train-rigid track system. Evaluation indices, derived from the power spectral density of the maglev train's response, are established to quantify both control stability and operational stability. Subsequently, based on these indices, a recommended range of PD control parameters is proposed, accounting for the requirements stipulated by the evaluation metrics. The study elucidates that variation in PD control parameters exert discernible effects on the system's stability, primarily altering the nature frequency and damping ratio. Specifically, control stability demonstrates a positive correlation with increasing PD control parameters, while operational stability exhibits a nuanced relationship—initially bolstered by escalating proportional coefficients but subsequently tempered, albeit gradually, with heightened derivative coefficients. The delineated range of values for PD control parameters is meticulously determined, considering pertinent physical parameters of the electromagnetic system, such as mass, static suspension current, and static suspension gap, alongside factors like the Sperling indicator and suspension gap variation.

Damping characteristics of High-Temperature superconducting pinning maglev levitation system

High-temperature superconducting (HTS) pinning maglev has achieved rapid development in recent decades. The levitation system of the HTS pinning maglev is mainly composed of Dewar with built-in HTS bulks and permanent magnet guideway (PMG). For a maglev transportation system, damping is important for vibration attenuation, and the inherent damping characteristics of the HTS pinning maglev system have not been evaluated clearly. In this paper, the damping characteristics of the HTS pinning maglev system are analyzed through experiments and simulations. Experiments are conducted to measure the dynamic responses of the system under free and forced vibrations. The logarithmic envelope method is used to evaluate the system damping under free vibration. The cross-correlation function is utilized to obtain the phase difference between the system vibration signal and excitation signal, and then calculate the system damping under forced vibration conditions. In addition, a two-dimensional finite element model including HTS bulks, PMG, and Dewar conductive shells is established to evaluate the damping force generated by each component during system vibrations. The additional eddy current damping of the conductive Dewar shell is considered and analyzed. Finally, from the perspective of system damping and thermal stability of HTS bulks, suggestions for selecting Dewar shell materials are proposed.

On the future sustainable ultra-high-speed maglev: A superconductor magnet technology enabling high energy efficiency and robustness

The blooming ultrahigh-speed SC maglev (superconducting magnetically levitated train) prompts green travel worldwide. We utilized high-temperature superconductor (HTS) magnets and have developed an energy-economical SC maglev prototype (Energ. Convers. Manage. (291)117247). In this paper, as a continuation, we further improve and maximize the performance of its key part – the HTS magnets, especially in compact high magnetic field and energy density operating conditions, by innovating an HTS magnet technology named the Shunted Extreme-NI Concept. The operational energy-robustness, -density, and -economy of HTS magnets, compared to the conventional type, are improved by 96.8%, 66.7%, and 52.5%, respectively. For a full-scale maglev equipped with this technology, the estimated energy consumption per passenger kilometer can be further reduced to below 20% of that of airplanes under the same cruising speed of 1000 km/h. This work is dedicated to advancing the energy performances of HTS magnets, heading to the future sustainable maglev transportation.

Maglev train high-precision positioning technology based on FBG array time division multiplexing

The positioning system is crucial in operating, controlling and monitoring maglev trains. This study proposes a maglev train positioning technology based on weak Fiber Bragg Grating (wFBG) sensing array time division multiplexing (TDM). The onboard Halbach permanent magnet array generates a traveling wave magnetic field that follows the train movement. The wFBG magnetic sensor array fixed on the track senses the magnetic field changes which cause periodical variation in sensors’ center wavelength. The relative position of the onboard Halbach array and the sensors on the track can be determined with the changes in center wavelength. Therefore, train positioning can be achieved. A rotating motor equipped with a circumferentially arranged magnet array is utilized for simulation experiment to verify the frequency response characteristics of the magnetic sensor. The result is that the operating frequency range of the sensor is at most 160 Hz so the sensor can be applied to positioning under the theoretical speed of 23 km/h. A small-scale experiment containing nine sensors is also conducted, which achieves relative positioning accuracy of 20 mm and absolute positioning accuracy of 540 mm, demonstrating the feasibility of the positioning technology. This study introduces the FBG TDM technology into maglev train positioning and provides new ideas about maglev train positioning.

High-performance cable materials for maglev trains prepared by the multiple synergistic regulation effects of the functionalized ionic liquids on EVA-based composites

High-performance cable materials for maglev trains prepared by the multiple synergistic regulation effects of the functionalized ionic liquids on EVA-based composites

Modeling and Analysis of a Novel Levitation Magnet with Damping Coils for High-Speed Maglev Train

Modeling and Analysis of a Novel Levitation Magnet with Damping Coils for High-Speed Maglev Train

Method for Predicting Linear Eddy Current Braking Performance of the High-Speed Maglev Train Based on Magnetic Circuit Structure

On high-speed magnetic levitation (maglev) trains, the linear eddy current brake (LECB) is a key piece of equipment to ensure the safety of train operation. In the event of a sudden failure of the traction motor or the external power grid, braking by the LECB, which comes with the maglev train, is currently the only emergency braking method that can ensure the train can be safely stopped while operating at high speed. The braking performance of eddy current brakes is usually predicted based on symmetrical magnetic equivalent circuits, which usually ignore the interactions between the magnetic circuits. For LECB, such interactions should not be neglected. In this paper, to investigate an accurate and efficient method for predicting the braking performance of LECB for high-speed maglev trains, based on the structural characteristics of LECB and Kirchhoff’s law, a full structural magnetic equivalent circuit model considering the interactions between magnetic circuits is developed, and then combined with the subdomain method, a braking force model, to predict the braking performance of LECB. The performance prediction of LECB with different numbers of magnetic poles is compared with the traditional method using the results of the finite element method and the experimental method as references. The results show that the proposed method is more accurate in predicting the braking performance of LECB and better reflects the physical characteristics of the actual magnetic field.

Comprehensive degree of nonlinearity in the dynamic response of high-speed Maglev train

The aim of this study is to propose a method for evaluating the comprehensive degree of nonlinearity in the dynamic response of high-speed maglev train system through mathematical modeling and numerical simulation. A model of a typical high-speed maglev vehicle is established based on the principles of maglev vehicle dynamics, and control models for the suspension magnet and the guide magnet are developed using principles from the electromagnetism and automatic control theory. The vibration responses of the vehicle system, including acceleration and electromagnetic forces are calculated using a fast numerical integration method. This calculation is performed for various control parameters and track harmonic excitations. The Hilbert-Huang transform (HHT) is adopted to decompose the response signal and derive the local mean frequency (amplitude) and instantaneous frequency (amplitude) of the response, based on which the Degree of Nonlinearity (DN) of the vibration response of a single component is obtained by calculating the deviation between the instantaneous frequency and the mean frequency. The Comprehensive Degree of Nonlinearity (CDN) of the vibration response in the maglev train system is proposed and defined by incorporating the DNs of the vertical and lateral vibrations of the carbody, bogie, suspension magnet and guide magnet, and by quantitatively evaluating them. The effects of the electromagnet control parameters and harmonic irregularities (wavelength and amplitude) of the track on the DN of each component and the CDN of the entire vehicle system are analyzed in detail. The analysis results show that the DN and CDN can demonstrate the extent of instability in the vehicle system and can be applied for safety warning on maglev vehicles.

Experimental study on the dynamic behavior of a new medium–low-speed maglev subgrade structure

Constructing medium–low-speed magnetic levitation (MLS maglev) subgrade by borrowing the construction standards of high-speed railway (HSR) subgrade can result in enormous engineering waste because the amplitude, distribution width, and dynamic coefficient of the dynamic load of MLS maglev trains are much smaller than those of HSR trains. To address this problem, an innovative subgrade structure was proposed to match the dynamic loads of MLS maglev trains. Two experimental models are constructed to study the proposed MLS maglev subgrade at train speeds of 100 km/h, 120 km/h, 160 km/h, and 200 km/h. The two models are labeled as Models I and II, and the only difference between these two models is the type of surface layer material of the subgrade bed, whereas the other structural features are the same. Specifically, the Model Ⅰ employs graded gravel, whereas the Model Ⅱ uses A group filling. The experimental results indicate that for both models, the dynamic earth pressure amplitudes are all less than 20 % of the subgrade’s self-weight at the bottom surface of the subgrade bed. In addition, the cumulative settlement of the two models is below the cumulative settlement limit. Although both models with the proposed MLS maglev subgrade exhibit excellent long-term performance, the Model Ⅰ has superior attenuation characteristics of dynamic earth pressure, and smaller acceleration and dynamic deformation than that the Model Ⅰ. This is attributed to the graded gravel used in the Model Ⅰ, which possesses a greater dynamic modulus and damping ratio than the A group filling used in the Model Ⅱ. The results presented in this study could contribute to the comprehension of the dynamic behavior of the subgrade under the dynamic loads of MLS maglev trains. More importantly, compared to the existing MLS maglev subgrades, the proposed MLS maglev subgrade has lower construction standards and is thus suitable for practical engineering applications.