Levitation Force Research Articles

Design of levitation controller for EMS maglev train with compensation of eddy current effect

ABSTRACT The Electro magnetic suspension (EMS) maglev train uses active control to achieve levitation stability, and the eddy current effect of the levitation electromagnet can make it difficult to adjust the control parameters of EMS maglev train, even affecting the levitation stability of EMS maglev train. Aiming at the control parameters of EMS maglev train under eddy current effect, an analytical expression of the levitation force considering eddy current effect was derived, and a single electromagnet levitation model was established. The influence of eddy current effect in the stability of open-loop levitation system was compared and analyzed. A fitting levitation control parameter was determined through a single levitation frame bench test, and the Simulink model of a single levitation frame was established. The different levitation control parameters effects considering eddy current effects at 200 km/h was studied comparatively, and a BP-PID adaptive controller was designed to adjust the controller parameters of EMS maglev train. The research results showed that the proposed BP-PID controller can effectively adjust control parameters to achieve effective compensation and optimization of the balance working point of the air gap caused by eddy current effect.

Design, Modeling, and Characteristics Analysis of Halbach Permanent Magnetic Spring

Magnetic springs, which can be used to replace traditional mechanical springs, have many advantages, such as necessitating no physical contact, generating no friction, no vibration or noise, and having a long lifespan. Nevertheless, their strong nonlinearity limits their widespread application. In this study, we developed a novel permanent magnet spring to address this issue: a Halbach permanent magnetic spring, with a large levitation force and an approximately linear force characteristic curve. First, we introduce the structure and the parameters of the Halbach permanent magnetic spring. Second, we describe the levitation force performance and the stiffness performance of the Halbach permanent magnetic spring using finite element analysis. Third, we analyze the trends through which different parameters influence the levitation force performance and stiffness performance. Finally, we provide recommendations for the future design of and improvement in the Halbach permanent magnetic spring.

Nondipole interaction between two uniformly magnetized spheres and its relation to superconducting levitation

Analytically solving the magnetostatic Maxwell equations in the bispherical coordinates, we calculate the magnetic field around two uniformly magnetized spheres oriented so that their magnetic moments are parallel to the axis passing through the centers of the spheres. We demonstrate that, contrary to what is often claimed in the literature, the magnetic interaction between such spheres is not equivalent to the interaction between two point magnetic dipoles placed in the centers of the spheres. The nonzero levitation force acting on a uniformly magnetized sphere or a point magnetic dipole above a superconducting sphere in the ideal Meissner state is a clear manifestation of the non-equivalence.

Effects on the Microstructure and Levitation Force Properties of Multi-Seeded YBCO Superconductors Using in Situ Self-Assembly Seeding Approach

Effects on the Microstructure and Levitation Force Properties of Multi-Seeded YBCO Superconductors Using in Situ Self-Assembly Seeding Approach

Dynamic Interaction Analysis of a Coupled System of Permanent Maglev Train and Flexible Track Beam

Vehicle–track beam coupling resonance greatly influences the vibration response of the suspended permanent (SPML) system. Therefore, the study established the coupled dynamic model of the SPML train and the track beam using. The model is used to analyze the dynamic response of SPML trains when passing through the long-span flexible track beam at resonance speed. The accuracy of the model was verified by field tests, which simulated and compared the dynamic responses of maglev train and track beam systems at different running speeds. Furthermore, the coupled vibration response of the train and track beam at resonant speed are investigated to gain insight into the mechanism and vibrational properties of the SPML system in a resonant background. It shows that the dominant frequency of the train, suspension frame, and track beam is 6.74[Formula: see text]Hz. They result in resonance in the SPML system at 30[Formula: see text]km/h. Further analysis shows that adjusting the vertical distance between the mass center of the vehicle and the track beam can effectively alleviate the resonance between the vehicle and the track. Additionally, deformation at the ends of the long-span track beams affects the levitation force and gap of the suspension frame, offering valuable guidance for SPML system design.

Halbach structure parameter optimization by Maxwell tensor method for PML in manned hybrid maglev

This paper presents an optimization of the Halbach structure parameters for the permanent magnetic levitation (PML) component in manned hybrid maglev system using Maxwell tensor method. The focus is on enhancing the levitation force and reducing the lateral stiffness, which are important for improving the system’s load capacity and lateral stability. Based on the analysis of the magnetic flux density formula as presented by Halbach (1985), seven structural parameters were reduced to four independent variables. The Maxwell tensor formulation enabled the derivation of analytical expressions for the levitation force and stiffness, leading to identification of parametier conbinations that maximize magneitc properties. Contour plots were constructed to visually demonstrate the impact of parameter variations on magnetic characteristics, including magnetic flux density, levitation force, and lateral stiffness. Ultimately, a series of optimization cases for structural parameters were proposed in accordance with the design requirements of the manned hybrid Maglev system, and these cases were comprehensively evaluated through contour plot analysis. Furthermore, the finite element software FEMM was utilized to model and validate the optimal cases, thereby confirming the effectiveness of the analytical expressions for magnetic properties and the optimization strategy. This research not only provides theoretical support for the design of PML components but also offers new insights into the optimization of magnetic characteristics for hybrid maglev systems.

Magnetic Properties of Improved Molar Ratio Y1.6Ba2.3Cu3.3O7-y Bulk Magnet

YBCO bulk superconductor was fabricated by the seed crystal growth method using a Sm1.8Ba2Cu3O7-y (Sm123) seed. The molar ratio of Y was increased in order to increase the flux pinning magnetic force. The density of Y211 phase, playing the role of flux pinning center for superconducting bulk magnetic force, was observed to increase in the microstructure of Y1.6Ba2.3Cu3.3O7-y specimens, as the composition of Y, constituting the superconducting bulk, increased. The measured superconducting critical current density of Y1.6Ba2.3Cu3.3O7-y superconducting bulk was 36,247 A/cm2, a 17% increase due to the increase of Y composition. The measured magnetic levitation force was 74 N, and the maximum trapped magnetic force was 2.56 kG. The superconducting magnetic force tended to increase as the Y composition in the bulk increased. The method of controlling the molar ratio of the elements constituting the superconductor bulk in this study seems to be an alternative to increase the magnetic force of superconducting bulk.

Comparison of Levitation Properties between Bulk High-Temperature Superconductor Blocks and High-Temperature Superconductor Tape Stacks Prepared from Commercial Coated Conductors.

Bulk high-temperature superconductors (HTSs) such as REBa2Cu3O7-x (REBCO, RE = Y, Gd) are commonly used in rotationally symmetric superconducting magnetic bearings. However, such bulks have several disadvantages such as brittleness, limited availability and high costs due to the time-consuming and energy-intensive fabrication process. Alternatively, tape stacks of HTS-coated conductors might be used for these devices promising an improved bearing efficiency due to a simplification of manufacturing processes for the required shapes, higher mechanical strength, improved thermal performance, higher availability and therefore potentially reduced costs. Hence, tape stacks with a base area of (12 × 12) mm2 and a height of up to 12 mm were prepared and compared to commercial bulks of the same size. The trapped field measurements at 77 K showed slightly higher values for the tape stacks if compared to bulks with the same size. Afterwards, the maximum levitation forces in zero field (ZFC) and field cooling (FC) modes were measured while approaching a permanent magnet, which allows the stiffness in the vertical and lateral directions to be determined. Similar levitation forces were measured in the vertical direction for bulk samples and tape stacks in ZFC and FC modes, whereas the lateral forces were almost zero for stacks with the REBCO films parallel to the magnet. A 90° rotation of the tape stacks with respect to the magnet results in the opposite behavior, i.e., a high lateral but negligible vertical stiffness. This anisotropy originates from the arrangement of decoupled superconducting layers in the tape stacks. Therefore, a combination of stacks with vertical and lateral alignment is required for stable levitation in a bearing.

Enhancing dynamic stability of HTS maglev systems with preloading method

High temperature superconducting (HTS) bulks have strong flux pinning capabilities and are widely used in various fields. Their self-stabilizing characteristics also provide new ideas for ultra-high-speed rail transit. For HTS maglev systems, operational stability, curve negotiation and safety when subjected to external forces are very important. Due to the hysteresis effect of superconducting bulks, they do not always return to their initial positions after deviating from the levitated position in an alternative external magnetic field. In some cases, the levitation system can be destroyed. Studies have shown that preloading can enhance quasi-static levitation performance. Therefore, this paper conducts a detailed analysis of the quasi-static levitation and guidance forces of HTS bulks above a Halbach permanent magnet guideway (PMG) under conditions with and without preloading. Additionally, the dynamic responses of the HTS bulks under lateral or vertical pulsed excitations are studied, with a particular focus on the final equilibrium position offset after disturbance. The results indicate that preloading can suppress the attenuation of the levitation force, enhance the guidance performance, and raise stiffness in both lateral and vertical directions. It also effectively suppresses position deviation from disturbance and increases the maximum excitation force threshold for system instability. This study provides practical insights for HTS maglev applications.

Modeling and dynamic performance of distributed force in high-temperature superconducting pinning magnetic levitation

High-temperature superconducting (HTS) pinning magnetic levitation (maglev) systems are highly promising for future applications in rail transportation. Through the interaction between onboard HTS bulks and the permanent magnet guideway (PMG), this system generates levitation and guidance forces, known as the HTS-PMG relationship. Under practical conditions, this interaction manifests itself as a distributed force. However, past models have only considered concentrated forces. This study aims to design experiments to investigate the HTS-PMG relationship and propose a more realistic discretized lateral-vertical coupling HTS-PMG relationship to accurately reflect torques in dynamic simulations. Based on this, a dynamic model is established to analyze the Sperling index and the five-degree-of-freedom dynamic response of the HTS pinning maglev vehicle system under different HTS-PMG relationship models. The results indicate that the proposed discretized lateral-vertical coupling HTS-PMG relationship accurately characterizes the torque generated by the HTS levitator, influencing lateral, roll, pitch, and yaw motions to some extent. Compared with the concentrated force model, the discrete force model exhibits superior dynamic performance, particularly in terms of lateral dynamics and the lateral Sperling index. This study provides valuable insights into the field of HTS maglev, particularly regarding investigating HTS-PMG relationships and their impact on HTS maglev system dynamic performance.

Orientation optimization of the Halbach PMG for the levitation and guidance performance of the HTS maglev system

High-temperature superconducting maglev technology has great application potential in rail transit applications due to its advantages such as passive stable levitation and green environmental protection. As one of the key components of the HTS maglev system, the Halbach-type permanent magnet guideway (PMG) enhances the magnetic field on one side of the guideway and weakens that on the other side. Optimizing the PMG, including the geometry and magnetic properties of the magnet, is an effective method to improve the levitation and guidance performance of the system. In addition, since NdFeB permanent magnets are expensive, optimizing the design of the PMG for the HTS maglev system is also an important work to reduce the application cost. In this paper, the Nelder–Mead Simplex method (NMS) in the optimization solver in COMSOL software is used to optimize the geometric parameters of the Halbach PMG according to the different objective requirements of the HTS maglev system. The optimization objectives include the maximum levitation force and guidance force under the constraint of the maximum cross-sectional area of the PMG, as well as the minimum cross-sectional area of the PMG with a minimum levitation force constraint. The results indicate that the NMS method is effective. By comparing four PMGs during the optimization process, it is found that this method can fully improve the utilization of the magnetic field by changing the geometric parameters of the Halbach PMG. This study can provide a valuable reference for the optimal design of the PMG for HTS maglev systems in the future.

Development of Simplified Methods for Levitation Force Distribution in Maglev Vehicles Using Frequency Ratio Tests.

Maglev vehicles apply the entire vehicle load uniformly onto bridges through levitation forces. In assessing the dynamic characteristics of the maglev train-bridge coupling system, it is reasonable to simplify the distributed levitation force as a concentrated force. This article theoretically derives the analytical response of bridge dynamics under the action of a single constant force and conducts numerical simulations for a moving single constant force and a series of equally spaced constant forces passing over simply supported beams and two-span continuous beams, respectively. The topic of discussion is the response of bridge dynamics when different degrees of force concentration are involved. High-precision displacement and acceleration sensors were utilized to conduct tests on the Shanghai maglev line to verify the accuracy of the simulation results. The results indicate that when simplifying the distributed levitation force into a concentrated force model, a frequency ratio can be used to analyze the conditions for resonance between the train and the bridge and to calculate the critical speed of the train; the levitation distribution force of a high-speed maglev vehicle can be simplified into four groups of concentrated forces based on the number of levitation frames to achieve sufficient accuracy, with the dynamic response of the bridge being close to that under distributed loads.

A fully superconducting magnetic bearing with a jointless coil excited by a superconducting dynamo

Abstract Superconducting magnetic bearings usually combine a setup of permanent magnets (PMs) and superconducting bulks. The bearing size is typically scaled up to increase the levitation force as the force density is limited in such setups due to the magnetic flux density and its spatial gradient. As alternative, the PMs might be replaced by a superconducting coil. To test this, jointless coils were prepared by a wind and flip technology using coated conductors of different tape manufacturers. The realized pancake coils were studied at liquid nitrogen temperature. Numerical simulations yielded a magnetic field of up to 0.5 T at 77 K for coils with a inner diameter of 20 mm. The prepared coils were charged with a superconducting dynamo, in which two magnet configurations were tested. A clear dependence on the magnet size and frequency was found for the charging characteristics. A magnetic field of about 0.3 T at 77 K was imprinted in one of the coils. However, a degradation of the coils was found over time indicated by some delamination at the cutted edges, which reduced the maximum achievable magnetic field after a few weeks. Nevertheless, a fully superconducting bearing was realized with by combining the jointless coil with an additional YBCO bulk. After charging the coil with the dynamo, a levitation force of up to 10 N at 77 K was measured under zero-field cooling conditions. The generated levitation force decayed only slightly after charging indicating low losses in the coil.

Numerical and experimental research on the hydro-electromagnetic levitation micropump

Micropump is the core component of the microfluidic systems. However, most mechanical micropumps are using the traditional contact bearings that are troubled by wear-out failure. Hydraulic levitation, which can make the rotating components levitate without any solid-solid contact, provides efficient solution to this long-standing challenge. Nevertheless, the current hydraulic levitation technology must utilize micron microgroove structure to produce thrust forces, therefore enlarging the assemble difficulty and manufacture cost. Alternatively, a novel kind of hydro-electromagnetic levitation micropump (HELP) without grooved thrust bearing is designed in this study. Taking advantage of the coupling behavior between the electromagnetic force and hydraulic force, the rotor of the HELP can levitate in the working fluid in all directions. Thereafter, the mechanisms of levitation forces formation are elucidated by the simulations of fluid flow and motor. Results indicate that the levitation bearing can provide sufficient load capacity in all working conditions, especially in high speeds. Based on the hydro-electromagnetic levitation principle, the HELP prototype is manufactured, whose overall size is as large as a coin, but can output the hydraulic performance of over 3160 mL/min and 90.5 kPa at 20000 RPM, which is several times over other micropumps. To verify the rotor levitation performance, the levitation trajectory test benches are built on the basis of laser displacement sensors. Results prove that the designed HELP can levitate stably in all directions at all rotational speeds. The proposed levitation micropump may be an excellent choice for powering the liquid cooling systems with high performance and high reliability.

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.

Behavior and effect of natural refinement of Sm2BaCuO5 derived from homogeneous nucleation catastrophe in bulks

AbstractAmong the REBa2Cu3O7‐δ (REBCO or RE123, RE = rare earth element) family, SmBCO is preferably used in top‐seeded melt‐growth (TSMG) because of its outstanding property and more controllable stoichiometry 123. Nevertheless, the refinement of Sm2BaCuO5 (Sm211) particles has been challenging for high‐performance SmBCO bulks. Conventional precursor powders (SmBa2Cu3O7‐δ plus Sm2BaCuO5) intrinsically result in enlarging Sm2BaCuO5 particles due to their coarsening and epitaxial growth during the heating process. Here, we used modified precursor powders (MPPs, Sm2O3 plus Ba2Cu3O5) in air‐processed TSMG, in which there is neither Sm211 in the beginning nor related enlargement during heating. Consequently, the nucleation catastrophe of Sm211 occurred above the peritectic temperature, which in situ formed, possessing naturally small size. Further, aiming to suppress the Sm/Ba substitution, Ba‐rich MPP, substituting Ba2Cu3O5 with Ba3Cu4O7) was employed, producing an excellent SmBCO bulk with a diameter of 24 mm: levitation force of 51.5 N and trapped field of 0.537 T. Optical micrographs and quantitative analyses confirmed the superior refinement and distribution of Sm211 particles in SmBCO bulks. Most importantly, new strategies in this work are widely applicable for developing cost‐effective and high‐performance other REBCO bulk superconductors.

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.

Modelling and analysis of a superconducting magnetic coupler used for cryogenic pump

AbstractIt is difficult to achieve low heat leakage and leak‐free rotary sealing for conventional small‐ and medium‐sized cryogenic liquid pumps (CLPs). This is because the motor in a room‐temperature environment is connected to the pump impeller (in a cryogenic environment) via a long transmission shaft. An axial flux‐concentration superconducting magnetic coupler (AFCSMC) is proposed for CLP to eliminate the transmission shaft. Firstly, the structure and the operation mechanism of AFCSMC are described. Then, a 2D electromagnetic modelling method for AFCSMC is established based on the H‐φ formulation and also validated experimentally in terms of the prediction on the levitation force and the guidance force. Thus, the 2D numerical simulations of AFCSMC are performed in an equivalent static system instead of the actual double rotor motion system in which the moving mesh is quite complicated. It is investigated that dependences of the transmission torque on the key electromagnetic structural parameters, such as permanent magnet arrangement, number of pole‐pairs, ferromagnetic yoke, operating slip, and so on. The results indicate that the average transmitting torque is less affected by the operating slip, and AFCSMC can start asynchronously and operate in steady state with a synchronous speed. With the advantages of low loss, risk‐free of desynchronising, and overload protection, the proposed AFCSMC can provide a competitive candidate for mechanical power transmission technologies in cryogenic engineering.

Non-Contact Multi-Degree-of-Freedom Motor Based on Hybrid Electromagnetic-Piezoelectric Drive Mode

A new non-contact ultrasonic motor consisting of a Langevin transducer, an electromagnetic device, and a spherical rotor is presented, and the designed motor is theoretically analysis and experimentally verified. The designed motor is driven by a mixture of near-field acoustic levitation and electromagnetism, and the electromagnetic platform is controlled by three stacked piezoelectric actuators to control the deflection direction, thus driving the spherical rotor to achieve the same angle of deflection and self-propagation. By exciting the Langevin transducer under the rotor, the high-frequency vibration of the stator disc causes the air between the stator disc and the rotor to be squeezed periodically, and when the air pressure in the gap is larger than the external atmospheric pressure, the levitation force generated by the stator is larger than the gravity of the rotor, thus levitating the rotor, and when the rotor deflects, it can still achieve stable levitation because of its special geometry. The proposed new motor is expected to be used in applications requiring high output torque and micro-displacement.

Stochastic evaluation of quasi-zero stiffness magnetic spring using a reluctance-corrected analytical model

—In state of the art high-precision motion systems, which utilize magnetic levitation, a quasi-zero stiffness gravity compensation is one of the essentials to improve dynamic performance, eliminate position dependency and thus simplify controller design. Special configurations of permanent magnets, such as Halbach magnet arrays, can realize magnetic levitation as a form of magnetic spring. However, unlike conventional permanent magnet machines with large stiffness, the quasi-zero stiffness magnetic spring requires higher modeling accuracy for force estimation, which is affected by the nonlinear reluctance effect of permanent magnets. In this study, we propose an accurate magnetic modeling method for the quasi-zero stiffness magnetic spring. By correcting the reluctance effect of magnets, the proposed magnetic model achieves superior accuracy estimating levitation force and stiffness to the conventional surface current model. Using the reluctance-corrected magnetic model, tolerance analysis was performed to identify dominant geometric parameters affecting the uncertainty of the Halbach array magnetic spring performance. A Monte-Carlo simulation was used to estimate the overall tolerance of magnetic forces and stiffness. The experimental results fit in the tolerances.