Levitation Force Research Articles

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.

Mechanical Analysis and Testing of Conduction-Cooled Superconducting Magnet for Levitation Force Measurement Application

High-temperature superconductors have great potential for various engineering applications such as a flywheel energy storage system. The levitation force of bulk YBCO superconductors can be drastically increased by increasing the strength of the external field. Therefore, a 6T conduction-cooled superconducting magnet has been developed for levitation force measurement application. Firstly, to protect the magnet from mechanical damage, reliable stress analysis inside the coil is paramount before the magnet is built and tested. Therefore, a 1/4 two-dimensional (2D) axisymmetric model of the magnet was established, and the mechanical stress in the whole process of winding, cooling down and energizing of the magnet was calculated. Then, the charging, discharging, and preliminary levitation force performance tests were performed to validate the operating stability of the magnet. According to the simulation results, the peak stresses of all coil models are within the allowable value and the winding maintains excellent mechanical stability in the superconducting magnet. The test results show that the superconducting magnet can be charged to its desired current of 150 A without quenching and maintain stable operation during the charging and discharging process. What is more, the superconducting magnet can meet the requirements for the levitation force measurement of both low magnetic field and high magnetic field.

An Effective Optimization Method and Implementation of Permanent Magnet Electrodynamic Wheel for Maglev Car

The levitation-propulsion integration ability of radial permanent magnet electrodynamic wheel (PM EDW) renders its competitive edge over other magnetic levitation systems. A low-cost and effective second induction method is proposed to target the synchronous improvement of the saturation speed, levitation and propulsion forces. Its effectiveness is determined from the small-scale EDW to the full-scale EDW via theoretical model, simulation analysis and experiments test. First, according to magnetic charge theory, an updated EDW is proposed and developed. Simulated and tested results of the small-scale EDW demonstrate that the levitation force, propulsion force and saturation speed are increased by 14%, 7% and 30%. This improvement benefits the increased induction current and the mitigated skin effect. Afterwards, further analysis of the full-scale EDW with rings of various conductivity and thickness is conducted. The levitation force, propulsion force and saturation speed are enhanced by more than 50%, 10% and 200% synchronously. Based on analysis of power loss under the same levitation and propulsion forces, the updated EDW is more efficient than the original EDW. Ultimately, a proof-of-principle prototype with the updated EDW and 4-m long guideway are developed. The multi-loop PID control strategy along with dynamic mode implementation methodology are introduced. The scaled prototype is levitated over guideway at 12 mm and the levitation-propulsion ability is implemented with the maximum acceleration of 1.25 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This proof-of-principle prototype with updated EDW and control strategy paves the way to engineering applications of Maglev car.

Dynamics of Separation of Unmanned Aerial Vehicles from the Magnetic Launcher Cart during Takeoff

Most aircraft launchers exhibit a rapid acceleration of the launching aircraft, often exceeding ten times the acceleration due to gravity. However, only magnetic launchers offer flexible control over the propulsion force of the launcher cart, enabling precise control over the aircraft’s acceleration and speed during its movement on the launcher. Consequently, extensive research is being conducted on magnetic launchers to ensure the repeatability of launch parameters, protect against aircraft overloads, and ensure operator safety. This article describes the process of modeling and analyzing the dynamical properties of a launch cart of an innovative prototype launcher, which employs a passive magnetic suspension with high-temperature superconductors, developed under the GABRIEL project. The developed mathematical model of the magnetic catapult cart was employed to conduct numerical studies of the longitudinal and lateral movement of the cart, as well as the configuration of the UAV–cart system during UAV takeoff under variable atmospheric conditions. An essential aspect of the research involved experimentally determining the magnetic levitation force generated by the superconductors as a function of the gap. The results obtained demonstrate that the analyzed catapult design enables safe UAV takeoff. External factors and potential vibrations resulting from uneven mass distribution in the UAV–cart system are effectively balanced by the magnetic forces arising from the Meissner effect and the flux pinning phenomenon. The primary advantage of the magnetic levitation catapult, in comparison to commercial catapults, lies in its ability to provide a reduced and consistent acceleration throughout the entire takeoff process.

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.

Enhancing magnetic levitation and guidance force and weight efficiency of high‐temperature superconducting maglev systems by using sliced bulk YBCO

AbstractWe aimed to enhance the magnetic force efficiency of Maglev systems without increasing total weight. For this aim, we divided YBCO bulks into three slices horizontally to utilize the YBCO‐permanent magnetic guideway (PMG) interaction surface as much as possible. We used whole YBCO above PMGs with different magnetic pole directions (PMG‐A and PMG‐B) in two lying positions of transversal and longitudinal and investigated levitation and guidance force performances. It is determined that levitation and guidance forces by using YBCO in transversal lying mode are bigger compared to the longitudinal mode. For sliced YBCO, the maximum levitation force increased by 69% and 78%, while the guidance force enhancements are determined as 212% and 91%, compared to the whole YBCO above PMG‐A and PMG‐B, respectively. The levitation and guidance force density with respect to the total mass of unit a set of slices YBCO increased by 92% and 106%, respectively, compared to the whole YBCO above PMG‐B in transversal mode. Since the higher levitation force and the lower total weight of the onboard unit are important parameters in point of the energy efficiency in Maglev and other levitation applications, the result of this study supplies useful data for the engineers and industrial partners.

Investigation of MgB2 bulk superconductors synthesized by in situ spark plasma sintering at different temperatures

In this research, the synthesis of MgB2 bulk superconductor with in-situ spark plasma sintering technique at different temperatures and the impacts of these sintering temperatures on the critical parameters (density, phase development, microstructure, transition temperature, critical current density and levitation force) of the superconductor were investigated. The optimum sintering temperature in terms of phase formation was found to be 850 °C. The maximum density was reached at 900 °C. It was determined that the critical temperatures of the samples sintered at 850 and 900 °C were around 39 K. It was found that the materials processed at different temperatures by in situ spark plasma sintering carry critical current densities of the order of 105 A/cm2 in the self-field and at 10 and 20 K. The maximum attractive and repulsive force are visible that there is not a linear relation with the sintering temperatures of samples.

Bulk MgB2 superconductor for levitation applications fabricated with boron processed by different routes

Bulk MgB2 discs were prepared by an in situ route from mixtures of magnesium and boron powders. The boron powders were produced by two methods. The first one consisted of a self-propagating high temperature magnesiothermic synthesis (SHS) process followed by acid and fluorine cleaning and a heat treatment in inert atmosphere. This approach produced boron with purities between 86 % and 97 %, where the main impurity was Mg. Depending on the final heat treatment, these boron powders were amorphous or crystalline. In the second route, high purity nano powders (99 %) of boron were obtained by a diborane pyrolysis process. Bulks of MgB2 were characterized by structural, microstructural, and magnetic measurements. Critical current density, pinning force aspects and levitation force (including guiding force) details were assessed. Amorphous lower purity boron (86–97 %) obtained by the first processing route was found to promote the largest levitation forces of the MgB2 bulks and, among these samples, the best levitation results were recorded when using boron with a purity of 95–97 %. Use of a lower purity boron that decreases the cost of MgB2 promotes large scale production at industrial level of bulk MgB2 superconducting magnets for levitation applications and enhances the applicability potential of MgB2 superconductor. The relationship between levitation force and specific features of the samples such as pinning force details are discussed.

Extended 2-D Magnetic Field Modeling of Linear Motor to Investigate the Magnetic Force Parameters of High-Speed Superconducting Maglev

A 2D numerical finite element model of a linear synchronous motor (LSM) is extended based on the magnetic field and moving mesh properties to investigate the magnetic flux and magnetic force characteristics of the high-speed EML Maglev system, by using HTS coils rather than lower current carrying copper coils on the onboard unit and PMs on the ground. In this 2D LSM model, the transient, time dependent solver is used to obtain the magnetic flux densities. Both the propulsion and levitation forces increased with increasing supercurrent J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> values indicating the advantage of using the superconducting windings in PM-LSM of Maglev vehicles as compared to the copper wires. It was also determined that although the propulsion force is obtained on a comparable level with the studies in literature, the lower levitation force issue than the EDS, despite the better propulsion to levitation force ratio, can be overcame by using the high flux trapping capacity bulk HTSs in the onboard unit together with the superconducting coils. The determined higher propulsion force in this PM-LSM Maglev model indicates that the Maglev vehicle can reach higher velocities in a short-distance and thus this vehicle can be effectively used in short-distance travels in addition to the long-distance transportation. On the other hand, since the EDS system to be accelerated in a certain time interval via conventional wheels to achieve sufficient levitation, PM-LSM system can be integrated into the EDS Maglev system to ensure higher acceleration in a short time interval in addition to the higher levitation and propulsion force performances.

Study on Electromagnetic Relationship and Dynamic Characteristics of Superconducting Electrodynamic Maglev Train on Curved Track

This study considers an electrodynamic maglev train of the MLX01 type as the research object. Equivalent circuit models of levitation/guidance were established, and forces in different directions were solved using the energy method A field-circuit-motion coupling numerical model of a single bogie and a ground coil was established. Based on the field-circuit-motion coupling model, the various electromagnetic relationship of maglev train on curved track was analyzed. The law of the electromagnetic spring coefficient and the internal mechanism under different electromagnetic parameters was explored. Considering the coupling characteristics between the electromagnetic forces, the characteristics of the levitation force and guidance force under different standard air gaps were analyzed, and a numerical fitting analysis was performed. On this basis, the laws of levitation force and guidance force with levitation displacement and guidance displacement, as well as the characteristics of drag force with operation speed under different standard air gaps, were studied. Meanwhile, the characteristics of the guidance-drag ratio and levitation-drag ratio were analyzed. A dynamic model with 20 degrees of freedom was established based on the analysis of the geometric model of the maglev train. Taking the track irregularity as the external excitation source of the bogie, the dynamic characteristics of the bogie and vehicle body under different standard air gaps and speeds were analyzed. The effects of different suspension damping and stiffness coefficients on the vibration characteristics of a vehicle body were studied. This provides important theoretical and data support for design and dynamic analysis of superconducting electrodynamic maglev trains.

Research on the self-levitation of cylindrical magnets with wrapped shells in magnetic fluid: Consideration magnetization direction of magnets

In this paper, the self-levitation of cylindrical magnets wrapped by shells immersed in magnetic fluid (MF) is studied. The calculation formula of the magnetic fluid levitation force (MFLF) received by magnets and shells is derived, and the dependence between MFLF, mass of MF, and levitation height of magnets is studied. Attention is paid to the influence of magnetization direction of magnets and shells on MFLF, and experiments have been designed to study MFLF. Research shows that both the magnetization direction of magnets and shells can affect MFLF, and the use of soft magnetic shells and radial magnetized magnets is beneficial to obtain a smaller axial MFLF. In addition, the magnetization direction of magnets has a significant influence on the distribution and surface instability of MF, which is a key factor affecting MFLF. There are two intervals in which the MFLF changes drastically for the axial magnetized magnets, but only one for the magnets with radial magnetization. The reason is that the surface instability of MF caused by axial magnetized magnets plays a significant role in axial MFLF, while the surface instability caused by radial magnetized magnets has almost no influence on axial MFLF.

Research on vibration mechanism of the low-to-medium-speed maglev train-track-at-ground-structure system

The at-ground-structure supports the maglev track on the subgrade segment and receives the subgrade’s equally distributed elastic support to ensure the holding track running of the maglev train. A complicated maglev train-track-at-ground-structure coupled system is produced, negatively affecting the stable operation of the train. To explore the vibration mechanism, an elaborate maglev train-track-at-ground-structure coupled system was established considering active levitation control, and field tests confirmed the reliability of the numerical method. Firstly, the natural frequencies of track-at-ground-structure were investigated. Then, characteristics of this coupled system were examined in terms of its dynamic interaction mechanism, dynamic response characteristics and vibration frequency spectrum distribution. Finally, the vehicle-induced resonance mechanism and anti-vibration methods of the at-ground-structure were analyzed. The results show that the high-frequency vibrations exist in both the F-rail and at-ground-structure obviously, and create varied wavelengths affecting the maglev train’s running stability. The high frequency resonance phenomena easily produce when loading frequency of neighboring levitation forces is near to fundamental frequency of at-ground-structure, and disappears while the two frequencies are avoided.

Modeling and Optimization of a Large-Load Magnetic Levitation Gravity Compensator

This article presents the modeling and optimization design of a large load magnetic levitation gravity compensator. The proposed magnetic levitation gravity compensator comprises three layers of two-dimensional (2D) permanent magnet arrays. The middle mover layer can generate a large passive levitation force to compensate for the gravity of large loads in some magnetic levitation systems, such as the measurement framework in lithography machines or large space optical equipment to be tested on the ground. To accurately predict the passive levitation force, an improved magnetic charge model is proposed, in which the actual working points of each permanent magnet (PM) are considered. The accuracy of the improved model is verified via three-dimensional (3D) finite element simulation. Genetic algorithm (GA) is then adopted as the parameter optimization method to reduce the levitation force stiffness within the effective vertical displacement to the greatest extent possible. Compared with the levitation force performance without parameter optimization, the sensitivity of the levitation force with vertical displacement is significantly reduced. In addition, the mechanical structure is designed, and the mechanical strength is checked. Finally, a magnetic levitation gravity compensator prototype with a passive levitation force of 6200 N is manufactured and tested. The tested values of the levitation force match well with the analytical and simulation results. The tested levitation force stiffness within 4 mm is less than 50 N&#x002F;mm and basically remains unchanged, which is a superior performance for magnetic levitation systems.

Research on Levitation Force Control of an Axial-flux Hybrid-Excitation Generator with PI-Based Torque Distribution

An asymmetric-primary axial-flux hybrid-excitation generator (APAFHG) has already been proposed to improve the starting performance of vertical axis wind turbines. However, the double-stator single-rotor structure causes a problem: different torque proportions create different rotor maglev forces, which will cause fluctuation and negatively impact the rotor bearing and even the operation of the wind power generation system. Therefore, a mathematical model considering the double-stator single-rotor structure and a proportional integral-based torque control strategy considering double-stator distribution are proposed in this paper to help APAFHG offer a good starting performance in vertical-axis wind power generation system and to stabilize maglev force generated by double-stator quadrature axis current simultaneously. Finally, the cooperation control of the maglev force and torque distribution is realized in MATLAB/Simulink, and the rotor maglev force will be relatively stable despite mechanical torque changes, which is a basis for the wind turbine to stably operate as the wind constantly fluctuates in vertical axis wind power system.

A novel magnetic circuit and structure for magnetic levitation ruler

The single axis linear displacement measurement system of CMM is composed of grating ruler, servo motor and linear motion mechanism. Although the measuring accuracy of grating ruler is high, the accuracy of servo motor and linear motion mechanism is low. Therefore, the complex structure limits the measurement accuracy of the linear displacement measurement system. This paper introduces a novel linear displacement measurement system named magnetic levitation ruler. According to the working principle of grating ruler and the characteristics of magnetic levitation technology, the magnetic circuit design and structural design of magnetic levitation ruler are completed in this paper. The mover core of the magnetic levitation ruler is in the stable working magnetic field provided by the stator yoke. The horizontal control coil wound on the mover core can obtain more stable ampere force to improve the control accuracy of the mover core displacement. Therefore, the mover core can be moved in step mode, and the length of each step is fixed. Each step is the minimum scale of the magnetic levitation ruler. Therefore, the mover core can implement displacement measurement while moving in a linear motion. This paper analyzes the working principle of levitation, horizontal motion, and displacement measurement of magnetic levitation ruler, and determines the structural materials and parameters of magnetic levitation ruler with the help of finite element analysis software. The simulation results show that the levitation force of the magnetic levitation ruler is proportional to the current passing through the levitation coils, and the thrust of the horizontal control coil is less disturbed by the magnetic field. Compared with the linear displacement measurement system with rotational servo motor or permanent magnet synchronous linear motor as the core, the magnetic levitation ruler has stable magnetic field, strong controllability, high integration, and is easier to achieve high-precision control.

Effect of partitioning YBaCuO bulk on the levitation force in Halbach external field

When a YBaCuO bulk superconductor (SC) is subdivided, its levitation force may not be significantly reduced after this partitioning process. The force will decrease even less if the sectional surface introduced by partitioning is parallel to the induced current loop. Moreover, the levitation force can be maintained because the partitioning makes the SC more magnetizable. These findings have implications for longitudinal maglev technology. A method for calculating levitation forces in nonuniform fields based on critical-state theory is proposed. In this method, an SC is divided into several regions where the external field is approximately uniform within each subvolume. To minimize the force degradation introduced by partitioning, the cutting surfaces should be parallel to the induced current. This approximate approach can effectively reproduce the experiment and improve the calculation accuracy. Another application of combining and recovering discrete SCs is demonstrated, and it is shown that a recombined SC according to the small-loss partitioning condition can achieve 68% of the levitation capacity of an intact sample. In addition, the invisible cracks inside the bulk sample can be predicted by comparing its levitation force with that of the intact sample.

Complex microstructural analysis of YBCO single-grain bulks with artificial holes: Effect on superconducting properties

This work presents an investigation of the microstructural and superconducting properties of standard single-grain bulk superconductor Y–Ba–Cu–O (YBCO) and samples fabricated with artificial holes. It was shown that the presence of artificial holes reduces the absolute porosity of the sample. The presence of artificial holes did not improve the homogeneity of oxygen distribution in the samples after oxygenation. The distribution of Y211 particles in the samples has a negligible effect on the macroscopic superconducting properties. In the process of crystal growth, the ellipticity of the introduced holes and their displacement in the direction of crystal growth in the growth sectors arise. Macroscopic superconducting properties, such as levitation force and trapped magnetic field at 77 K, were supplemented by magnetization measurements of superconducting transition temperature and critical current density. The levitation force and the trapped magnetic field were higher for the sample with holes. For the measured trapped magnetic field, the decrease of the porosity in the a-growth sectors, which have a higher volume fraction of Y2BaCuO5 (Y211) particles, and consequently stronger pinning, is significant.

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.

Design accuracy and magnetic field analysis of a dual-armature bearingless flux reversal motor

A dual-armature bearingless flux reversal motor (DBFRM) is proposed. The permanent magnet in the motor is located on the stator side, the armature winding is located on the stator side and the rotor side, the suspension winding is located at the stator side, the rotor teeth are embedded in the slotted non-magnetic material rotor barrel, and the stator and rotor cores are made of laminated silicon steel. The DBFRM demonstrates the characteristics of high speed, long life, and fast dynamic response and has unique advantages in power energy saving and energy storage. Compared with the traditional bearingless flux reversal motor, the DBFRM shows better fault tolerance. Based on the theory of air-gap magnetic field modulation, the torque and the levitation mechanism of the motor are expounded from four perspectives—permanent magnetic field, armature reaction magnetic field, electromagnetic torque, and levitation force—which lays the foundation for the establishment of an accurate mathematical model of levitation force and torque.

Permanent Magnet Electrodynamic Suspensions Applied to MAGLEV Transportation Systems: A Review

This article reviews permanent magnet electrodynamic suspensions (PM-EDSs) used in ground transportation systems, such as Magnetic Levitation (MAGLEV) trains. The different suspension topologies are first presented, considering separately their two main components, namely the track and the magnetic field source. Beyond that, a phenomenological explanation of the evolution with the speed of the drag and levitation forces is provided, depending on the track topology. The models aimed at predicting the behavior and performance of the suspension are then detailed, classifying them according to whether they are global or local. Finally, the main experimental setups developed to validate PM-EDSs are described.