Field-cooling Height Research Articles

Machine learning driven optimization and parameter selection of multi-surface HTS Maglev

This research aims to tackle the challenges posed by precise force measurement for high temperature superconducting (HTS) Maglev systems, including mechanical constraints, step motor limitations, and sensor resolutions. For this aim, six machine learning (ML) models namely Support Vector Machine (SVM), Gaussian Process Regression (GPR), Extreme Gradient Boosting (XGB), Long Short-Term Memory (LSTM), Extreme Machine Learning (EML), and Convolutional Neural Network (CNN) were developed to predict levitation force (Fz) and lateral force (Fx) based on process parameters including permanent magnet width (PMW), field cooling height (FCH), the movement in the z-axis (vertical distance), and the movement in the x-axis (lateral distance). Among six ML models, CNN emerged as the most accurate model, demonstrating smaller root mean square deviation (RMSD) without compromising correlation coefficients. Furthermore, an innovative process window approach was introduced to select process parameters that simultaneously meet the minimum value of Fz and maximum value of Fx, named β1 and β2, set at 90 N and 0 N, respectively. Within this window, PMW of 30 mm and z values less than 10 mm were found to be consistent for all FCH and x values. The novelty of this study is to formulate the optimisation problem in HTS Maglev using the developed ML model by addressing two specific objectives one of which focuses on maximizing Fz while ensuring Fx remains within a defined tolerance (β3), representing the minimum allowable ratio of the levitation force to the total force, and the second problem aims to maximize Fz while obtaining zero Fx. The optimum PMW, FCH, x, and z values were obtained at 30 mm, 30 mm, 4 mm and 5 mm, corresponding to Fz and Fx values of 224.2 N and -53.8 N for option 1. As for option 2, the process parameters were obtained as 28.6 mm, 25.9 mm, 0 mm, and 5 mm, corresponding to Fz and Fx values of 194.2 N and 0 N. It was obtained both experimentally and by the optimization that Fz reaches close its maximum as the Fx gains attractive character. Hence, it is expected that the outcomes of this study will significantly benefit the design of HTS Maglev systems and find valuable applications across various transportation engineering projects.

Levitation Force Compensation Study for HTS Maglev System Based on the Input of Electromagnetic Force

The advantages of levitation and guidance integration make the high-temperature superconducting (HTS) maglev system have great potential in the field of high-speed transportation. However, due to the influence of some factors such as the Dewar (a low temperature thermostat for superconductors) vacuum increases and magnetic field irregularity, the levitation force will decline and working height will drop. To solve the problems, this paper proposes a compensation method based on electromagnetic auxiliary device. Firstly, the thought and purpose of this method are explained in detail. Secondly, the effectiveness of levitation force compensation is verified by experiment. Then, electromagnetic simulation model is established and its correctness is verified by comparing simulation results and experimental data. Finally, dynamic simulation is conducted based on the verified model to study the vibration characteristics of Dewar system. The results show that the auxiliary device can compensate the levitation force and suppress vibration well. Meanwhile, comparing with the field cooling height (FCH) at 20 mm and 30 mm, the compensation effect of former is better than latter, but the overall maximum levitation force of latter is higher than former. This research provides an economical and effective way to achieve the levitation force compensation of HTS maglev system. Furthermore, the electromagnetic auxiliary device is an active energy input port, providing the possibility for the active control of HTS system. It is expected to provide reference for future practice in relevant application fields.

Working temperature threshold analysis for HTS maglev system based the novel thermal-dynamic levitation force coupling measurement device

The previous researches show that the temperature rises inside the high temperature superconducting (HTS) bulk will affect the levitation performance of the HTS bulk. In order to further explore the relationship between the internal temperature rise and the levitation force of the HTS bulk, a thermal-dynamic levitation force coupling measurement device is reformed, and the Halbach PM wheel is used to generate alternating MF at field cooling height (FCH) 30/40 mm, working height (WH) 8/12 mm and speed from 500 rpm to 3500 rpm with intervals of 500 rpm, to study the influence of MF fluctuation on the temperature rise and levitation force of the HTS bulk. The temperature values are obtained when the levitation force decays greatly (82 K) and fails (87 K). The experimental results can provide theoretical suggestions for the irregularity standard of PMG and reference for the protection of the HTS pinning maglev system.

Pumping sequence effect on levitation and guidance forces of YBCO bulks for evacuated tube transportation

As a part of high temperature superconducting Maglev-evacuated tube transport (HTS Maglev-ETT), ETT technology provides a potential new solution to realize the proposition of higher ground speed transportation. In this system, due to the low pressure caused by tube evacuation, the temperature of liquid nitrogen (LN2) changes and ultimately affects the performance of HTS bulks. Considering the significant necessity to guarantee HTS Maglev-ETT operational stability and safety, this paper focuses on the levitation and guidance performance variations of YBCO bulks caused by the pumping sequence under low pressure. One working condition is to pump the air out during the field cooling stage before levitating the vehicle, defined as “evacuating and then levitating” (E-L case). The other working condition is to pump the air out after the field cooling stage when the vehicle is already levitated, defined as “levitating and then evacuating” (L-E case). Based on the superconducting maglev measurement system (SCML-01) and a self-developed ambient pressure-reducing platform, the working conditions’ effect on levitation and guidance force in the two sequences above is experimentally explored. Simultaneously, the difference between the two sequences is also discussed specifically. For a larger levitation force, the E-L case with high field cooling height (FCH) and low working height (WH) is an efficient condition; The L-E case with low FCH and low WH is suitable for a larger guidance force. In addition, the two specific conditions perform better under lower air pressure. All these conclusions are anticipated to provide a reference for practical startup procedures and future engineering design of HTS Maglev-ETT systems.

Magnetic Force Performance of Hybrid Multisurface HTS Maglev System With Auxiliary Onboard PMs

The vertical levitation force, guidance force, and magnetic stiffness values, and thus the loading capacity and movement stability of high-temperature superconducting (HTS) Maglev systems, are aimed to be increased in this study by using auxiliary permanent magnets (PMs) in the onboard unit together with the multisurface HTS-permanent magnetic guideway (PMG) arrangement (hybrid multisurface arrangement). First, the magnetic levitation force, guidance force, and stiffness performances of the hybrid multisurface arrangement were investigated at different field cooling heights (FCH). Then, to compensate for the negation of instability that results from the higher repulsive force between the onboard PMs and the PMG and to obtain an optimal magnetic field medium, we have changed the vertical position of the auxiliary onboard PMs (Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> ) to Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> = 0, 2, and 4 mm, at the cost of a bit of adecrement in the vertical levitation force. The bigger levitation force, together with the guidance force values for FCH = 25 mm and Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> = 0 mm, indicates that the hybrid multisurface HTS–PMG arrangements are beneficial to increasing the practical applicability of Maglev systems.

Vertical Nonlinear Damping Experiments and Identification of High Temperature Superconducting Levitation Above Permanent Magnet Track

High temperature superconducting (HTS) magnetic levitation (maglev) train has the potential to become the next generation of high-speed rail transport due to its passive stabilization and virtually no magnetic resistance. From the maglev dynamics views, the damping between the levitated superconductor and the permanent magnet will play an important role to the further vehicle bogie design. The early experiments on HTS maglev damping illustrates that the data was very small in the no-load conditions and lacks the significant exploration of the practical-employed three-seed YBCO bulk as the levitator material. In addition, the empirical expression of the damping coefficient and the working height is still unsolved for applications. Focusing on the vertical damping of the HTS levitator levitated above the practical Halbach magnet track, a vertical vibration damping test bench is designed to conduct experiments in free levitation. Firstly, the effects of three main working factors like load, field cooling height (FCH) and excitation strength, on the vertical damping of the HTS levitation are investigated under different experimental loads. It is interesting to find the HTS levitation shows strong damping behaviors during the practical load operations above the magnet track. Based on the experimental data and theoretical analysis, the vertical damping of the HTS Maglev engineering vehicle is derived as 2×104 Ns/m, which can be close to that of a superconducting electrodynamic levitation vehicle. Secondly, the empirical formula of damping-working height is established by combining the experimental data with the theoretical formula model. It is found that the excitation strength affects the decay of damping but has little effect on the damping magnitude. Furthermore, the phenomenon of keeping constant damping ratio at the same FCH is found even though the other conditions change. This paper show evidences that the HTS maglev system is not a weakly damped system and has a strong nonlinearity in the vertical damping. The proposed empirical formula can provide reference for the bogie design of HTS maglev train.

Dynamic guidance performance of HTS bulk under varying external magnetic field

With the unique flux pinning characteristics, high temperature superconducting (HTS) bulk can stably levitate above the permanent magnet guideway (PMG). Moreover, owing to its advantages of environmental protection, frictionless and pollution-free, the HTS maglev has shown significant potential in high-speed rail transit. At present, HTS maglev technology is at a critical moment from laboratory research to engineering application. Among the numerous parameters related to its engineering application, the curve negotiation ability determined by the guidance performance of the HTS bulk superconductors is crucial to the safety and stability of its operation. Thus, in this paper, we experimentally investigated the dynamic guidance force of the HTS bulks under different operational conditions including different rotational speeds, maximum lateral displacement (MLD), field cooling height (FCH), and working height (WH) based on a customized HTS maglev dynamic measurement system (SCML-03). In addition, the dynamic guidance force of HTS bulk under long-time operation was studied. It is concluded that FCH, WH, and MLD are intimately associated with the dynamic guidance performance of the HTS bulk, while the rotational speed of the circular PMG has little influence on it. Namely, to improve the dynamic guidance performance of the HTS bulk, reducing the FCH and increasing the WH properly can be regarded as an effective method. Eventually, this research also verifies the long-term lateral stability of the HTS maglev system during dynamic operation.

Loading capacity, rotation loss and torsional oscillation research on an Evershed-type hybrid superconducting bearing used for micro-thrust measurements

Characterized by their very low rotational drag, applications of high-temperature superconductor (HTS) bearings have been expanded in some high-precision instruments. We have developed a sensitive magnetic suspension stand based on an Evershed-type hybrid HTS bearing to measure μN-level thrust. The hybrid HTS bearing uses the strong attractive force of a permanent magnet (PM)-biased bearing to support the main load in the bearing, while instability in the PM-biased bearing is compensated by the magnetic stability from a HTS bearing. Compared with a single PM/HTS bearing, the hybrid HTS bearing is intended not only to support larger loads but also to suppress rotation loss and levitation drift. Loading capacity, loss and damping torque were explored for different design parameters such as bearing gaps L 1, L 2 and the field cooling height (FCH) of bulk HTSs. Spin-down testing suggested that the loss of a hybrid HTS bearing can be reduced by increasing the HTS bearing gap L 2 or reducing the FCH. The hybrid HTS bearing showed a typical oscillation behavior at extreme low frequencies, and torsional pendulum testing suggested that the spring constant k of the hybrid HTS bearing can be as low as 36.39 μN m deg–1. A micro-thrust stand based on the hybrid HTS bearing was established to test an electrospray thruster in a vacuum chamber, and the measurement result of 26.61 μN shows the ability of the micro-thrust stand to achieve μN level testing.

Dynamic Response of HTS Pinning Maglev System Under High Frequency Excitation

The full-size high temperature superconducting (HTS) pinning magnetic levitation (maglev) prototype train was launched in SWJTU, Chengdu, China in 2021. This prototype has shown the basic load and low speed operation capacity of HTS pinning maglev train. Hence, the next important issue should be its dynamical performance under high-speed. Moreover, in the same track condition, higher speed usually brings higher frequency excitation, which becomes the major vibration cause of the HTS pinning maglev system. Therefore, this paper will mainly focus on this point to study the dynamic response of the HTS pinning maglev system under high frequency. Initially, an experiment is designed to measure the vibration response signal under the external excitation in different directions. Secondly, the responses of the system in each direction under different excitation frequencies are compared. Finally, the vertical, lateral and coupling response of the system under high frequency in different field cooling height (FCH) are analyzed. The result verifies that the HTS pinning maglev can effectively isolate the high frequency vibration. And compared to the vertical excitation, the lateral excitations can affect the dynamic performance of the system to a greater extent. This study suggests the smoothness requirement of the operating line in high-speed, as well as providing references for future dynamic studies and design of HTS pinning maglev system.

Experimental and Numerical Investigation of Levitation Force Parameters of Novel Multisurface Halbach HTS–PMG Arrangement for Superconducting Maglev System

We have designed multisurface Halbach high temperature superconductor-permanent magnetic guideway (HTS-PMG) arrangements for magnetically levitated transportation (Maglev) and investigated the static force parameters in addition to the dynamic response characteristics. Three different Halbach HTS-PMG arrangements were used with multisurface (6 HTS, 4 HTS) and single surface (2 HTS) configurations and static and dynamic measurements were carried out in three different field cooling heights (FCHs). The bigger vertical loading capacity and wider loading gap were obtained with multisurface Halbach HTS-PMG arrangements. In addition, nearly four times bigger guidance force values of multisurface arrangements than that of single surface one indicates that the side HTSs in multisurface arrangements make a significant contribution to the guidance force and thus lateral movement stability of Maglev systems. Both the vertical and lateral dynamic stiffness values increased with decreasing FCH and it can be also said that the dynamic stiffness properties of Maglev systems can be enhanced especially in lateral direction by using the multisurface Halbach HTS-PMG arrangements. Understanding of these experimental observations is supported by dedicated theoretical modelling through a 2-D approximation of the system. We show that by using a single material parameter (the critical current density <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>c</b></sub> ) for the whole superconducting set, one may satisfactorily predict the complete series of experiments. The static and dynamic parameters obtained from this study and the results of dedicated theoretical modeling for single-surface and multisurface HTS-PMG arrangements are thought to be helpful for the researchers working on static and dynamic performances of HTS Maglev systems.

Design and Experimental Studies on Superconducting Maglev Systems With Multisurface HTS–PMG Arrangements

In this article, we have designed and constructed a new multisurface (MS) high temperature superconductor (HTS) Maglev measurement system to investigate the enhancement of magnetic force properties of Maglev systems via MS HTS configurations above conventional permanent magnetic guideway (PMG). We have investigated both the static force and stiffness behavior and dynamic response characteristics of these MS HTS-PMG arrangements in different field cooling heights (FCHs). Optimum cooling height is determined as FCH 20-30 for both six- and four-HTS configurations. The maximum levitation force values of HTS-PMG arrangement with six-HTS were obtained bigger than that of four-HTS in the unit cryostat volume of MS arrangement, indicating that the HTSs at the bottom side of the cryostat make contribution to the loading capacity of Maglev systems. In the present article, it is observed that the magnetic flux density of bottom surface in addition to upper surface of the PMG can make a contribution to loading performance, vertical and lateral stability of Maglev systems. It is thought that the designed measurement facility and results of this study will be beneficial to increase the magnetic flux density in the unit volume via MS HTS-PMG arrangements for future design and construction of the HTS Maglev systems.

Magnetic Resistance of HTS Maglev Moving Above a Permanent Magnet Guideway with Large Magnetic Field Fluctuations

Unlike the magnetic levitation characteristics that most research focuses on, this article focuses on the magnetic resistance of high-temperature superconductor (HTS) maglev system. By superimposing iron sheets on the permanent magnet (PM) track to create significant magnetic field fluctuations, we studied the magnetic resistance of HTS-PM maglev caused by the fluctuating magnetic field, and used the rotating orbit platform to study the influence of the running speed and the field cooling height (FCH) on the magnetic resistance. The magnetic resistance is found mainly originating from the self-stabilizing characteristic of type II superconductor in an uneven external magnetic field, showing oscillation characteristics near a certain equilibrium value, with nearly constant amplitude at a given FCH and running speed. Spectrum analysis shows that the main frequency of the oscillation is the same as the frequency of the alternating magnetic field received by the maglev vehicle during running above the fluctuating magnetic field, revealing that this is a forced vibration driven by a fluctuating magnetic field. The oscillation amplitude and power density increase steadily with the increase of FCH, and show the characteristics of first increasing and then reaching saturation with the increase of running speed. The research results reveal that there is an inherent correlation between the oscillation of the magnetic resistance and the stability of the system.

Dynamic Characteristics of Levitated YBCO Bulk Running Above the Permanent Magnet Guideway With Fluctuating Magnetic Field

The dynamic characteristics of high-Tc superconducting magnetic levitation train (HTS-Maglev) are of great significance for future engineering applications. In this article, the dynamic characteristics of the HTS-Maglev are studied by measuring the variation amplitude of the levitation force on the running speed using an HTS-Maglev levitation simulation platform, where the distribution of the magnetic field of the permanent magnet track is uneven. The stability of the superconducting bulk at various running speeds and with different field cooling heights (FCHs) is analyzed by using the time domain, frequency domain, and Lyapunov exponent calculation. The levitation force is found reduced by the fluctuated magnetic field as the FCH is larger than the working height. The unstable phenomena of the system are observed at a running speed equivalent to a driving frequency of 25, 400, 466, and 490 Hz. The movement of the YBCO bulk shows typical chaotic characteristics with a positive Lyapunov exponent when the FCH is greater than 50 mm and the running speed reaches 180 km/h.

Lateral drift of the HTS Maglev vehicle running on a ring test line under low pressure environment

With the development in recent years, high temperature superconducting (HTS) Maglev with self-stabilization characteristic has been regarded as a good candidate for evacuated tube transport (ETT). To ensure the safety and stability of the HTS Maglev vehicle running in a low pressure environment, results measured in the latest research of an HTS Maglev-ETT Test System were used to study the lateral drift (LD) of the Maglev vehicle under different low pressures. The field cooling heights (FCHs) of 20 mm, 30 mm, and 40 mm were studied under each pressure condition. The experimental results show that the low pressure environment and an appropriately low FCH condition are both beneficial to suppress the LD phenomenon. The low pressure environment will reduce the LD by lowering the temperature of the liquid nitrogen and increasing the pinning potential energy U0 of HTS bulk. The basic data of the pressure effects on the HTS Maglev system at different FCHs proves the low-pressure environment can improve the operating characteristics and further demonstrates the superiority of the HTS Maglev-ETT system.

Levitation Height Drifts of HTS Bulks under a Long-Term External Disturbance

High-temperature superconducting (HTS) maglev owns the capability of passive stabilization and has the potential to operate at a high speed with low energy consumption. However, the excitation caused by the irregular surface and inhomogeneous magnetic field of the permanent magnet guideway (PMG) will result in vibration between the superconductors and PMG, which could lead to some stability problems such as drift. To study the reliability of HTS maglev systems under a long-term disturbance, a tailored experimental device composed of a vibration table, a fixture, and HTS maglev model was employed. The effects of field-cooling height (FCH), external excitation frequencies, and amplitudes on the levitation height drift were investigated. It is found that under the same operating conditions, large excitation amplitude, high frequency, and low FCH would lead to a greater levitation height drift. There are three kinds of drift trends, i.e., downward, upward, or downward at first and then upward, and the phenomenon of drifting upward is more likely to occur under small excitation amplitude, high frequency, and low FCH conditions. Meanwhile, two simulation models employing the flux flow model and the flux flow and creep model were applied respectively. The simulation results show that the flux flow and creep model are more consistent with the experimental phenomena and the flux flow has a greater influence on the drift in the initial time period, while the flux creep has a slighter impact on the drift for a long time. These researches reveal the levitation height drift rules of the HTS maglev system and introduce proper simulation model for levitation height drift so that this work provides a reference for the design and safe operation of HTS maglev vehicles.

Guidance Force and Its Hysteresis of YBCO Bulks Under a Low-Pressure Environment

High temperature superconducting (HTS) maglev train running in the evacuated tube is a new kind of transportation with great potential. The HTS bulks are core component of the HTS maglev train, and its guidance performance is crucial to the ability of curve-passing. Therefore, it is necessary to study the guidance force of YBCO bulks under a low-pressure environment. Based on the test system of magnetic levitation characteristics under low-pressure environments, the super-cooling state of liquid nitrogen is realized by the method of evacuation. The guidance force of YBCO bulks moving laterally above a Halbach permanent magnetic guideway was measured under different pressure values (100, 60, 40, 20 kPa). Results show that decreasing pressure is beneficial to improve the guidance performance of YBCO bulks. When the field cooling height (FCH) is under 35 mm, the guidance force increases with the decrease of the pressure. However, when the FCH is more than 35 mm, the guidance force decreases with the decrease of the pressure. Furthermore, decreasing FCH and pressure value can decrease hysteresis of guidance force and enhance the lateral stability of the HTS maglev system.

Vibration Suppression of High-Temperature Superconducting Maglev System via Electromagnetic Shunt Damper

The high-temperature superconducting (HTS) maglev system is characterized with self-stable levitation, low energy consumption, and pollution-free operation, and it has been considered as a promising technology for implementing high-speed transport systems. But the previous studies have shown that the damping of such system is relatively low, which indicates the large-amplitude nonlinear vibration may occur easily under external disturbances and affect the long-term motion stability, operation safety, and comfort of HTS maglev in rail transit application. In order to suppress the harmful vibration, an electromagnetic shunt damper (EMSD) was designed and incorporated into the HTS maglev system. Compared with other systems which employ the EMSD to diminish the vibration, the HTS maglev system does not need to set up external devices to supply magnetic field for the damper, because the permanent magnet guideway (PMG) in this system is directly taken advantages of. The natural frequency of the damper is adjusted to a value close to that of the maglev system. In this way, the damper becomes most effective because the moving vehicle body and the circuit resonate simultaneously. The feasibility of the damper was demonstrated through systematic experiments, and the effects of different field cooling heights (FCHs) of the HTS maglev system on EMSD’s performance were experimentally studied as well. Also, how the change of resistors in the EMSD circuit affects its working efficiency was preliminarily explored in this work. The results show that under the definite external disturbance, the damper can effectively attenuate the acceleration of vibration, furthermore, and it is found that the damper works better in condition of lower FCH. Within the scope of our experiments, the EMSD with a resistor in lower resistance performs better as results have shown. This investigation indicates that the vehicle will run in a more smooth and comfortable way along the track with this damper. The work is important for the further practical application of the technology.

Trapped Field and Levitation Performance of a YBCO Superconductor Magnetized in Different External Magnetic Fields

In order to find a relative preferable method to improve the trapped magnetic field (Btrap) of a YBCO superconductor, the influences of field-cooling height (FCH), magnetization intensity, and magnetization process on the trapped fields of the high temperature superconductor (HTS) magnetized in the magnetic fields of the permanent magnet guideway (PMG) and the superconducting magnet (SM) were both studied. In addition, the levitation forces of the bulk magnetized in the two different magnetic fields were also investigated in this paper. The experimental results showed that the maximum trapped field ratio (δtrap) of the bulk magnetized above the PMG attained the largest value, when the initial FCH was 30 mm. The remagnetization process was a preferable method to increase the Btrap, in the case that the FCH was higher than 30 mm. When the exciting current (Ie) of the SM was smaller than 15 A, the remagnetization process was an effective method to improve the Btrap. The remagnetization performance of the bulk attained the saturation, under the condition that the Ie was larger than 15 A. In the aspect of the levitation performance, it can be found that the decreasing amplitude of the force with the Btrap became larger, when the levitation gap was lower. The force acted on the bulk increased with increasing the magnetic fields of the SM. Moreover, the results also indicated that the initial Btrap was larger; the maximum levitation force (Flmax) became smaller. The magnetic hysteresis of the bulk was found to decrease with increasing the Btrap.

High-Temperature Superconducting Magnetic Levitation Vehicles: Dynamic Characteristics While Running on a Ring Test Line

In the long-distance operation of the high-temperature superconducting (HTS) magnetic levitation (maglev) systems, the dynamic characteristics of the vehicle are closely related to its security and stationarity, which require in-depth research to ensure its safe operation. Thus, we investigated the dynamic characteristics of the HTS maglev and assessed its safety and stationarity when running on a ring test line. In the experiments, the important parameters related to safety are lateral displacement (LD) and levitation height (LH). Results show that an appropriate low field-cooling height (FCH) is beneficial for its safe operation, and the maximum LD (MLD) should be considered in vehicle designs. Moreover, in other experiments, we tested the vibration acceleration of the HTS maglev vehicle using acceleration sensors and assessed its stationarity according to the Chinese National Standard GB5599-85, which is specifically published to assess the stationarity and security of railway vehicles by the China Ministry of Railways. The stationarity of the HTS maglev vehicle running on the ring test line is of good grade. When the secondary suspension and appropriate measures of vibration reduction are considered, the stationarity will be greatly improved.

Dynamic response characteristics of high temperature superconducting maglev systems: Comparison between Halbach-type and normal permanent magnet guideways

The permanent magnet guideway (PMG) is very important for the performance of the high temperature superconducting (HTS) system in terms of electromagnetic force and operational stability. The dynamic response characteristics of a HTS maglev model levitating on two types of PMG, which are the normal PMG with iron flux concentration and Halbach-type PMG, were investigated by experiments. The dynamic signals for different field-cooling heights (FCHs) and loading/unloading processes were acquired and analyzed by a vibration analyzer and laser displacement sensors. The resonant frequency, stiffness and levitation height of the model were discussed. It was found that the maglev model on the Halbach-type PMG has higher resonant frequency and higher vertical stiffness compared with the normal PMG. However, the low lateral stiffness of the model on the Halbach-type PMG indicates poor lateral stability. Besides, the Halbach-type PMG has better loading capacity than the normal PMG. These results are helpful to design a suitable PMG for the HTS system in practical applications.