Superconducting Maglev Vehicle Research Articles

Motion and thermal stability for high-temperature superconducting maglev vehicle under extreme crosswind conditions

Motion and thermal stability for high-temperature superconducting maglev vehicle under extreme crosswind conditions

Levitation performance evolution of high-temperature superconducting maglev vehicle under electromagnetism-heat-force strong coupling

ABSTRACT High-temperature superconducting (HTS) maglev is considered suitable for high-speed maglev systems because of its self-stability characteristic. However, when the HTS maglev vehicle vibrates, alternating current loss occurs in the onboard superconductor due to the change in the external magnetic field. It leads to the decrease of vehicle levitation height and seriously affects the safe and stable operation of the vehicle. So, in this paper, the levitation performance evolution of HTS maglev vehicle under the electromagnetism-heat-force strong coupling model is studied. The parameter of the air spring is optimized according to the ride index and levitation height decay. The effects of random irregularity at different speeds on vehicle levitation performance are compared. The influence of periodicity geometric irregularity on the levitation performance and ride comfort of HTS maglev vehicle are studied. This paper can provide data reference for the HTS maglev vehicle system in future engineering applications.

Investigation on thermal effect of bulk high-temperature superconductors under varying external magnetic field

Superconducting bulks applied to high-temperature superconducting (HTS) maglev vehicles are susceptible to magnetic field, resulting in alternating current (AC) losses and heat generation, which affect the stability of the suspension system. Therefore, the thermal effect of superconducting bulk under external magnetic field is worth studying. The paper uses finite element software to establish a 2D electromagnetic-thermal coupling model. The distribution and variation of HTS bulks’ temperature under varying external magnetic field are simulated and analyzed, and the loss and temperature rise of rectangular bulks with different thicknesses are studied. Finally, the effect of increasing the critical current density on the thermal effect of the superconducting bulk is discussed. The results show that the temperature rise of bulk has a positive correlation with the amplitude and frequency of external magnetic field. The maximum temperature is affected by the angle of magnetic field. Under the same external magnetic field, the bulk with smaller thickness produces smaller loss and temperature rise. The research results can provide important references for the operation and furniture design of HTS maglev vehicles.

<b>Evaluation of Vibration Resistance of Levitation and Guidance Ground Coils by Electromagnetic Excitation Tests Using a Superconducting Magnet</b>

During superconducting Maglev vehicles running, ground coils vibrate due to the reaction force of levitation force and guidance force. In electromagnetic excitation tests, a ground coil is vibrated under the strong magnetic field of a superconducting magnet. This paper describes an examination of test conditions based on numerical analysis, a processing method for energizing only the unit coil to be evaluated, and the electromagnetic excitation test results of the levitation and guidance coil. The vibration resistance of levitation and guidance ground coils were evaluated by electromagnetic excitation tests.

Influence of Traction Rod Arrangement on the Dynamic Performance of High-Temperature Superconducting Maglev Vehicle

High temperature superconducting (HTS) maglev, which uses the magnetic flux pinning effect to realize the levitation and operation, has attracted wide attention in the field of transportation due to its advantages of high efficiency, energy saving, safety and comfort. As the connection components between the bogie and vehicle body, and the transmission components of tractive and brake force, traction rods not only satisfy the relative motion between vehicle body and the bogie, but withstand the pounding of bogie relative to body as well. There is a great need to research the influence of traction rod parameters to HTS vehicle on its dynamic performance, which can prolong the life of the traction transmission device and enhance the running stability of vehicles. In this paper, a vehicle-bridge coupled dynamics model, considering different traction device arrangements, is established by means of multibody dynamics software Universal Mechanism (UM). And the influence of the traction transmission devices on the vehicle's dynamic performance is analyzed. The analysis results provide a reference for designing and optimizing the parameter of traction drive transmission devices.

The SCML-05 Developed for Studying the 3D Force and PMG Irregularities Characteristics of HTS Maglev

In order to promote the application of high temperature superconducting (HTS) maglev vehicle, the series of superconducting maglev (SCML) measurement devices — 01, 02 & 03 have been developed in Southwest Jiaotong University. During the course of research, the importance of three-dimensional (3D) study of the interaction between HTS bulks and permanent magnet guideways (PMGs) has become evident. More specifically, when the HTS vehicle is moving at a high speed, small irregularities of the PMG's magnetic field become the source of vibration. Therefore, in order to study the 3D force and the characteristics of HTS maglev under PMG irregularities, a new measurement device called SCML-05 was designed, constructed, and validated. This newly developed measurement device consists of two major parts. The first one is a closed-loop sliding platform providing 3D motion. The second part is measurement and data acquisition system with the software developed for this purpose. In addition, a laser displacement sensor is used to measure the geometry irregularities of the PMG. Overall, the SCML-05 is flexible and light. The force characteristics of the HTS bulks placed above the PMG can be precisely investigated by means of this system. Additionally, the PMG irregularities including geometry and magnetic field irregularities can be measured. These parameters are required to analyze the relationship between the PMG irregularities and the force of HTS maglev vehicle. The test process and typical results obtained by this system are presented in this paper.

Design of the Onboard Cryogenic System for High-Temperature Superconducting Maglev Vehicle

In the high-temperature superconducting (HTS) maglev system, the cryogenic system is used to eliminate the thermal load of the low-temperature unit in time to maintain the superconducting state of the superconductor, which is the prerequisite of the application. At present, liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) immersion cryogenic system is used in HTS maglev vehicles, but the operation efficiency of the vehicles will be reduced because of the LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> replenishment. Therefore, according to the application environment of HTS maglev vehicles, an onboard LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> natural circulation cryogenic system based on the principle of thermosiphon is designed. This paper focuses on the design of the structure of the cryogenic box, including the design of the vacuum system, the selection of refrigerator, the design of heat exchanger, and the selection of materials. Finally, it is calculated that the thermal load of the cryogenic system during the normal operation of the HTS maglev vehicle is 25.09 W, which is less than the cooling capacity of 120 W when the cryogenic system is working at 65 K. The feasibility of the cryogenic system is verified, which will provide a reference for the design of the cryogenic system in the engineering of the HTS maglev vehicles.

Vibration Characteristics of the New High-Temperature Superconducting Maglev Vehicle Based on Operation Test

A new HTS maglev vehicle called “KENYON” that can carry 8 passengers was successfully developed in December 2019. The vehicle adopted the bogie structure of independent running gear, which brings the improvement of curve passing performance. In order to further optimize vehicle curve passing performance in view of the small radius curve of the ring test line, corresponding experimental research was carried out in this paper. The experimental results show that the small wheelbase and centripetal arrangement were beneficial to improve the vehicle's curve passing ability.

Active vibration control of secondary suspension based on high-temperature superconducting maglev vehicle system

The high-temperature superconducting (HTS) magnetic levitation (maglev) vehicle system is a kind of self-stable levitation mode, which is benefited from the characteristic of flux pinning of non-ideal type II superconductor. And this novel prototype has the outstanding advantages of simple structure, reliable principle, friendly environment and so on. But in the HTS maglev vehicle system, the damping coefficients of the primary suspension are very small. The vibration of the YBCO bulks over a permanent magnet guideway (PMG) will be incurred by the fluctuant external magnetic field, which is easily transmitted to the car body to affect the running comfort. The primary goal of this paper is to apply active vibration control into two linear electromagnetic actuators on each bogie. Each electromagnetic actuator is combined with an air spring as a kind of active suspension system in secondary suspension. Initially, the primary suspension stiffness coefficient and damping coefficient of YBCO bulks are measured by experiments. And the mathematical model of HTS maglev vehicle with active actuators was built using the German track spectrum of low interference as PMG irregularity. Then, the dynamic responses of HTS maglev vehicle system were simulated with PID and Fuzzy-PID controllers used in the active actuator to verify the feasibility of the control methods, and compared with the uncontrolled system. Finally, the results of the simulation indicate that both control strategies could improve vehicle comfortable and greatly improve the stability of the system compared to the passive bogie system.

Design and Implementation of auto-filling liquid nitrogen for HTS maglev vehicles based on Kalman filter algorithm

The cryostat equipped with superconducting materials is one of the most important component of high-temperature superconducting maglev vehicles. However, due to the multiple energy disturbance forms in the cryostat, such as AC losses of superconductors, vibration of the cryostat and so on, the evaporation of liquid nitrogen (LN2) will be stimulated to accelerate, which will seriously threaten the vehicle safety. Therefore, this paper designs an intelligent controller which can realize the function of auto-filling LN2 based on the Kalman filter (KF) algorithm. Moreover, in this publication the corresponding methodology will be described as well in detail. Initially, the platinum resistance sensors were used to study the relationship between the temperature and LN2 level, meanwhile, the system state equation and observation equation were established. Then, the KF algorithm was introduced to estimate the true LN2 level. Based on the feedback signal of LN2 level, the system utilizes the STM32 microprocessor as control chip to control the solenoid valves and realizes the function of auto-filling. The controller has been implemented and the total time for filling one cryostat was reduced from 86 min to 16 min. This result is very encouraging and inspiring for the practical application of HTS maglev systems.

Study on Flux-Pinned Load Characteristics of High Temperature Superconducting Maglev Vehicle

With the distinctive pinned effects, the high temperature superconducting magnetic levitation vehicle is characterized by its high-performance self-stability, strong anti-interference ability and non-contact features, which are worthy of being studied in detail. In this paper, the high temperature superconducting maglev test platform in Southwest Jiaotong University was utilized to study the flux-pinned force. The calibration of vertical and lateral load characteristic curve under corresponding quasi-static conditions were conducted firstly, then it was transformed through polynomial fitting. In addition, the variation law of flux-pinned force under straight and curved tracks at different running speeds of maglev vehicle was attained based on the experiment.

Levitation Performance of the Second-Generation HTS Maglev Vehicle Serving in a Ring Test Line

Based on the decades of research, the second-generation high temperature superconducting (HTS) maglev vehicle was developed for continuously running on a ring test line. In this paper, the levitation performance of the entire HTS maglev vehicle was studied. The levitation force of the entire vehicle composed of four maglev cryostats was measured in field cooling heights of 20, 30, and 40 mm. The experimental results showed that the levitation force of the HTS maglev vehicle exceeds 10 000 N at a 12 mm levitation height, which means that the vehicle can achieve a load capability of 1 t/m. In addition, the levitation height decay of the HTS maglev vehicle was studied during operating at a low speed. Some levitation height decay was found after running for a period of time. To reduce the levitation height decay, the preload method was introduced to the maglev vehicle system. It was found that the proper preload method is beneficial for reducing the levitation height decay.

Dynamic Liquid Nitrogen Level Detection of Cryostats Onboard the HTS Maglev Vehicle

For the safe operation of high-temperature superconducting (HTS) Maglev vehicles, the liquid nitrogen (LN2) level in the onboard cryostat should be monitored in real-time during the whole running process. The previous method of LN2 level detection was proposed by using resistance sensors or liquid volume meters as the testing equipment to estimate the liquid level. However, the fluctuation of LN2 level causes great disturbance for the liquid level detection, which leads to unsteady detection and loss of valid data. In this paper, an effective method for LN2 level detection under dynamic conditions is proposed. First, the static evaporation of LN2 in rectangular and circular containers are measured by PT100 platinum resistances. And then, a self-developed simple hardware is designed for onboard cryostats, further improving the HTS maglev vehicle performance. Furthermore, the state estimation theory, which uses particle filter algorithm, is employed to eliminate the interference caused by fluctuation of the LN2 level. The real-time measurement results illustrate that the proposed dynamic liquid nitrogen level detection is able to meet the requirements of the LN2 level detection with high precision.

&lt;b&gt;Characteristics of Magnetic Springs for Guidance of Superconducting Maglev Vehicles&lt;/b&gt;

&lt;b&gt;Characteristics of Magnetic Springs for Guidance of Superconducting Maglev Vehicles&lt;/b&gt;

Study on Electromagnetic Force Characteristics Acting on Levitation/Guidance Coils of a Superconducting Maglev Vehicle System

Superconducting Maglev has been developed as a high-speed transport system. Superconducting coils (SC coils) are installed on the vehicle, and levitation/guidance coils (LG coils) are installed on the ground. A null-flux-type electrodynamic suspension system provided by electromagnetic interaction between SC coils and LG coils serves as the levitation and guidance functions of the vehicle system. Electromagnetic forces acting on SC coils are related to levitation and guidance functions of the vehicle. These forces were studied in previous research, and characteristics of levitation and guidance forces were revealed with respect to parameters of the design of the vehicle. On the other hand, electromagnetic forces acting on LG coils also exist as action–reaction pairs with the forces acting on SC coils. The forces act on LG coils in every levitated run of the vehicle, and stress is applied on the conductor and molded resin of the LG coils. In conventional studies, the vehicle design has been decided mainly by the electromagnetic forces acting on SC coils, and not by the forces acting on LG coils. The aim of the study is to establish an improved method to design the vehicle system with the objective of not only optimization of characteristics of the vehicle, but also consideration of stress on LG coils. As a preliminary study to establish the improved method, a study by computer simulation on characteristics of electromagnetic forces acting on LG coils with respect to the parameters of the vehicle is described in this paper.

Field homogeneity improvement of maglev NdFeB magnetic rails from joints.

An ideal magnetic rail should provide a homogeneous magnetic field along the longitudinal direction to guarantee the reliable friction-free operation of high temperature superconducting (HTS) maglev vehicles. But in reality, magnetic field inhomogeneity may occur due to lots of reasons; the joint gap is the most direct one. Joint gaps inevitably exist between adjacent segments and influence the longitudinal magnetic field homogeneity above the rail since any magnetic rails are consisting of many permanent magnet segments. To improve the running performance of maglev systems, two new rail joints are proposed based on the normal rail joint, which are named as mitered rail joint and overlapped rail joint. It is found that the overlapped rail joint has a better effect to provide a competitive homogeneous magnetic field. And the further structure optimization has been done to ensure maglev vehicle operation as stable as possible when passing through those joint gaps. The results show that the overlapped rail joint with optimal parameters can significantly reduce the magnetic field inhomogeneity comparing with the other two rail joints. In addition, an appropriate gap was suggested when balancing the thermal expansion of magnets and homogenous magnetic field, which is considered valuable references for the future design of the magnetic rails.

Study on the Magnetic Field Inhomogeneity of a Halbach Permanent-Magnet Guideway Due to Different Defects

The track regularity of a permanent-magnet guideway (PMG) is an important issue to ensure the riding comfort and running stability of high-temperature superconducting (HTS) maglev vehicles. Compared with defects of typical railway tracks, similar defects on PMG could affect the magnetic field at the levitation height and then influence the running performance and the riding comfort of the maglev system. In this paper, the influence of four kinds of Halbach PMG defects on magnetic field distribution was investigated by a finite-element simulation method. According to the calculation results, it is found that the sensitivity of the magnetic field inhomogeneity varies with each kind of defect. The vibration experiments found that the magnetic field inhomogeneity does bring vibration to HTS maglev vehicles. The results could provide significant references for future PMG design in the HTS maglev system.

希土類系高温超電導磁石搭載時の磁気浮上式鉄道車両の起磁力制御に関する検討

希土類系高温超電導磁石搭載時の磁気浮上式鉄道車両の起磁力制御に関する検討

Optimization of the Superconducting Linear Magnetic Bearing of a Maglev Vehicle

Considering the need for cost/performance prediction and optimization of superconducting maglev vehicles, we develop and validate here a 3D finite element model to simulate superconducting linear magnetic bearings. Then we reduce the 3D model to a 2D model in order to decrease the computing time. This allows us to perform in a reasonable time a stochastic optimization considering the superconductor properties and the vehicle operation. We look for the permanent magnet guideway geometry that minimizes the cost and maximizes the lateral force during a displacement sequence, with a constraint on the minimum levitation force. The displacement sequence reproduces a regular maglev vehicle operation with both vertical and lateral movements. For the sake of comparison, our reference is the SupraTrans prototype bearing. The results of the optimization suggest that the bearing cost could be substantially reduced, while keeping the same performances as the initial design. Alternatively, the performances could be significantly improved for the same original cost.

Levitation Performance of Rectangular Bulk Superconductor Arrays Above Applied Permanent-Magnet Guideways

Bulk high-temperature superconductors with a rectangular shape are easy to realize a compact assembly, which is promising for maglev applications. In order to find a reasonable array pattern, we have studied the levitation force of four multiseeded rectangular YBaCuO blocks with three possible arrays above two different permanent-magnet guideways (PMGs). Experimental results show that the levitation force can be improved by optimizing the array pattern of the bulk superconductors. An effective method to improve the utilization rate of the applied magnetic field is to avoid the joint air gaps between bulks located in a strong magnetic field area of the PMG. The optimal array pattern is able to enhance the levitation performance of the present superconducting maglev vehicle.