Stable Levitation Research Articles

Three-Dimensional Active Magnetic Levitation Actuating and Control System for Curved Pipes

A three-dimensional active maglev (magnetic levitation) actuating system based on force imbalance is proposed. By combining the principle of force imbalance control with the control algorithm, the stable levitation and controllable levitating motion of the magnetic ball can be realized. The four electromagnetic actuating structures are used to stabilize the force of the controlled object, and the dual-hall sensor group and hardware differential method are used to improve control stability and accuracy. By combining the fine adjustment of the active maglev actuating system with the coarse adjustment of the mechanical arm, the three-dimensional levitation motion of the magnetic ball in curved pipes is realized. Experimental results show that the proposed control algorithm solves problems such as the increase of deviation between the controlled object and the steady-state operating point and the rapid deterioration of tracking performance in the model-based control method. In the vertical direction, the overshoot is within 0.418%, regardless of axis motion or non-axis motion. In the horizontal direction, the offset limits left and right of the axis are 4.590 mm and 3.536 mm, respectively. The fluctuation of vertical and horizontal motion is within the allowable range of ±0.2 mm. This can be applied to the non-destructive quality detection of the inner walls and the internal dredging of long and thin pipes in examinations and industrial fields.

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.

Magnetic levitation in the field of a rotating dipole.

It is well known that two permanent magnets of fixed orientation will either always repel or attract one another regardless of the distance between them. However, if one magnet is rotated at sufficient speed, a stable position at a given equilibrium distance can exist for a second free magnet. The equilibrium is produced by magnetic forces alone, which are strong enough to maintain a levitating state under gravity. We show that a stable levitation can be obtained when the rotating magnet is tilted from the rotation axis, with no offset in its position. In this regime, the levitating magnet remains centered and its spinning rate remains negligible, while its magnetic moment precesses in synchronization with the driving magnet. We provide a physical explanation of the levitation through a model relying on static dipolar interactions between the two magnets and present experimental results which validate the proposed theory.

Experimental evaluation on dynamic performance of medium–low-speed maglev vehicle running on low-positioned subgrade

ABSTRACT As a novel urban rail transit system with relatively low construction costs, medium–low-speed maglev transportation is currently experiencing rapid development in China. However, there have been rare studies on the experiments of medium–low-speed maglev vehicle passing curves and low-positioned subgrade. Therefore, this paper systematically conducts on-site dynamic tests on the Qingyuan Maglev Tourism Line. The experiment provides a detailed analysis of the dynamic characteristics of the vehicle system and subgrade under varying speeds up to 132 km/h. The study explores the impacts of operating speed, track layout, and type of girder structure. The results indicate that a significant increase in operating speed and the application of emergency braking intensify the dynamic response of the vehicle system. When passing through the R700m curve and low-positioned subgrade sections at different speeds, the primary vibration frequency of the sprung structure is below 2.5 hz, while the unsprung structure shows a wide frequency distribution. The peak frequencies of the vibration for the low-positioned subgrade are mainly distributed in the 60–140 hz range, and the vibration response of the girder remains at a low level. The Sperling index values, levitation gap, and lateral offset of the levitation electromagnet of the testing vehicle do not exceed 2.5, 4 mm, and 10 mm, respectively, indicating excellent ride comfort and stable levitation performance. The results of this test study provide a reliable assessment of the safety of the vehicle and subgrade system and would help precise modelling of vehicle and subgrade system in the future.

MightyLev: An acoustic levitator for high-temperature containerless processing of medium- to high-density materials.

"MightyLev," a new multi-emitter ultrasonic acoustic levitation device capable of extremely stable levitation of materials of density up to at least 11.3g cm-3, is described. The exceptional stability of medium- to high-density samples levitated in MightyLev makes the device highly suitable for chemical and structural analysis using micro-focused spectroscopic and x-ray scattering techniques. In combination with mid-infrared laser heating, MightyLev is capable of levitating metallic and oxide materials during high-temperature cycling and melting above 1500K. Instabilities in particle confinement during heating were investigated by directly visualizing the acoustic field using schlieren imaging. The results reveal jets of hot-air directed along the anti-nodes of the acoustic field. The reaction force on the sample from the jet, coupled with the restoring force of the acoustic trap, generates a parametric lateral oscillation of the sample. This result provides valuable insight for future optimization and wider application of acoustic levitation for high-temperature containerless material processing.

Stable Levitation of Single-point Levitation Systems for Maglev Trains by Improved Cascade Control

The stable levitation of single-point levitation systems for electromagnetic suspension (EMS) maglev trains, which belongs to the control task of nonlinear and unstable systems, is investigated in this paper. Considering the simplicity and convenience of the control application, we dedicate ourselves to combining and applying common control methods to achieve the stable levitation rather than designing complex controls or using advanced control methods. For this goal, the single-point levitation system is divided into an electromagnetic system and a motion system first. On this basis, we design the Lyapunov controller and sliding mode controller as Controller I, while another Lyapunov controller and the standard Proportional Integral Derivative (PID) controller are designed as Controller II, which are used to control the electromagnetic system and motion system respectively and constitute the improved cascade control to achieve the stable levitation. Furthermore, the switching controller consisting of the standard PID controller and the designed Lyapunov controller is used as Controller II for the improvement of both stability and robustness.

Contactless surface tension measurement of molten oxides using oscillating drop method in an aerodynamic levitator

Aerodynamic levitation stands as a contactless method for thermophysical property measurement of molten oxides at high temperatures, offering the advantage of eliminating sample contamination and enabling surface tension measurement through the oscillating drop method. However, the presence of oscillation mode splitting results in an underestimation of surface tension. By improving levitation stability and optimizing the acoustic excitation method for the levitated drops, this study successfully eliminates oscillation mode splitting for the first time. The l = 2 resonance frequency is directly measured, which is used to calculate surface tension according to the Rayleigh equation. Taking Al2O3 as a representative of oxides, this study demonstrates the accurate surface tension measurement during the frequency scan process when oscillation mode splitting is absent. Additionally, combining damped oscillation analysis with the frequency scan reduces measurement uncertainty from 2.8 % to 1.5 %. Within the temperature range of 2336K–2923K, the surface tension of molten Al2O3 is determined to be γ = −(4.071 ± 2.688) × 10−5 (T-2327)+(0.7465 ± 0.074) N/m. Underestimation of surface tension is prevented when the l = 2 resonance frequency is used for surface tension calculations. The frequency crossover method which is used for surface tension measurement is also found to be affected by oscillation mode splitting.

On the instability of single-axis acoustic levitation under radial perturbations

Acoustic levitation is widely used in non-container measurement and non-contact manipulation. Particles in the single-axis acoustic levitation are easily unstable in the radial direction under external perturbations. In order to explore the instability in the acoustic levitation during radial perturbations, a nonlinear acoustic levitation model considering the coupling of radial and axial vibration is proposed to analyze the dominant factors influencing the levitation stability, an acoustic levitation system consisting of a transducer and a plane reflector is established, and high-speed photography is used to observe the vibration behavior of the particle with large radial vibration and the levitation stability. The simulation results are compared and verified with the experiments, which indicate that the reduction in axial trapping stiffness due to radial vibration plays a vital role in the levitation instability. The present model can characterize the radial anti-interference ability of different levitators as well as predict the movement trajectories of levitated particles after being disturbed, which is helpful to optimize the design of acoustic levitators and provide guidance for acoustic manipulation.

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.

Linear Model Predictive Control and Back-Propagation Controller for Single-Point Magnetic Levitation with Different Gap Levitation and Back-Propagation Offline Iteration

Magnetic suspension balance systems (MSBSs) need to allow vehicle models to levitate stably in different attitudes, so it is difficult to ensure the stable performance of the system under different levitation gaps using a controller designed with single balance point linearization. In this paper, a levitation controller based on linear model predictive control and a back-propagation neural network (LMPC-BP) is proposed and simulated for single-point magnetic levitation. The deviation of the BP network is observed and compensated by an expansion state observer (ESO). The iterative BP neural network model is further updated using current data and feedback data from the ESO, and then the performance of the LMPC-BP controller is evaluated before and after the update. The simulation results show that the LMPC-BP controller can achieve stable levitation at different gaps of the single-point magnetic levitation system. With further updating and iteration of the BP network, the controller anti-jamming performance is improved.

The Effect of the Movement of a Passive Reflector on the Atomization of a Levitating Drop

Abstract This study investigates the instability of distilled water drops under acoustic levitation induced by the movement of a reflector toward the transducer. The experimental setup consisted of a passive concave reflector and a Langevin transducer in a uniaxial-resonance configuration. The experiment consists of achieving a stable levitation of the droplet and then moving the reflector constantly toward the transducer, shortening the distance h between them (reflector-transducer). All experiments were recorded using a high-speed camera to analyze the drop’s behavior. The results revealed three distinct instabilities: radial atomization occurred when the drop volume (VD ) was ≤ 3.74 μl, beyond which central atomization was observed. A third instability is observed when a low reflector velocity (Vr < 0.67 mm/s) is used, where the droplet exhibited modes of oscillation with pulsed central atomization.

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.

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

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

Development of a new technological scheme of the carousel milking platform based on the principles of magnetic levitation

The Carousel, the most capital–intensive and loaded milking unit, is a rotating platform that carries a large mechanical load. Its own weight, combined with the weight of the animals being moved, can reach 1200 kg per milking place or more. To reduce friction in the wheeled systems of high-loaded vehicles, large-sized assemblies and mechanisms of machinery and equipment, including agricultural machinery and aggregates, the use of magnetic suspension technology is promising. The research was carried out in order to develop a new technological scheme of a levitating rotating milking platform Carousel based on the principles of magnetic levitation. The creation of a fundamentally new resource-saving design of the Carousel milking platform based on the principles of magnetic levitation in order to increase its reliability and reduce operating costs due to the exclusion of wear on the propellers of the rail-wheel system is possible. A new scheme of a rotating milking platform Carousel using permanent magnet magnetic suspension technology without the use of wheel thrusters is proposed. Its force calculation was performed in the main mode of steady motion with the platform fully filled with animals and partially filled at the beginning and end of the milking cycle of animals, obtaining basic equations for determining the necessary repulsive forces in horizontal and vertical magnetic assemblies providing magnetic levitation (suspension) and lateral stabilization (centering) of the rotating platform.

Nonlinear dynamics of diamagnetically levitating resonators

The ultimate isolation offered by levitation provides new opportunities for studying fundamental science and realizing ultra-sensitive floating sensors. Among different levitation schemes, diamagnetic levitation is attractive because it allows stable levitation at room temperature without a continuous power supply. While the dynamics of diamagnetically levitating objects in the linear regime are well studied, their nonlinear dynamics have received little attention. Here, we experimentally and theoretically study the nonlinear dynamic response of graphite resonators that levitate in permanent magnetic traps. By large amplitude actuation, we drive the resonators into nonlinear regime and measure their motion using laser Doppler interferometry. Unlike other magnetic levitation systems, here we observe a resonance frequency reduction with amplitude in a diamagnetic levitation system that we attribute to the softening effect of the magnetic force. We then analyze the asymmetric magnetic potential and construct a model that captures the experimental nonlinear dynamic behavior over a wide range of excitation forces. We also investigate the linearity of the damping forces on the levitating resonator, and show that although eddy current damping remains linear over a large range, gas damping opens a route for tuning nonlinear damping forces via the squeeze-film effect.

A novel boost power converter suitable for bearingless switched reluctance motor with wider rotor teeth

Abstract Aiming at the problem that the excitation current build-up speed of the bearingless switched reluctance motor with wider rotor teeth (BSRMWR) is too slow during commutation, this paper proposes a simple structured boost power converter. When the motor is commutation, it uses the winding demagnetization energy to quickly establish the excitation current for the latter phase winding and realizes the low torque ripple operation of the motor on the basis of ensuring the stable levitation of the motor. The topology and working status of the novel power converter are analyzed. On this basis, a 12/8 pole single-winding BSRMWR driving system based on the novel boost power converter is constructed. Through Matlab/Simulink simulation, the feasibility and effectiveness of the novel power converter are verified.

Performance Optimization of Maglev Train’s Electromagnetic Levitation System: Control Structure and Algorithm

This article investigates the performance optimization structure and algorithm of the electromagnetic levitation (EML) system. Firstly, a functionalized control structure is proposed by the incremental attachment of a controller gain system. Under this control structure, the predesigned controller is designed for nominal performance while the controller gain system handles performance optimization. This is of great help because the system trajectory of the highly dynamic and open-loop unstable EML system can be contained in the admissible region during the optimization of the controller gain system. Secondly, it is demonstrated that optimizing the incrementally attached controller gain system (under the proposed control structure) for performance optimization is equivalent to optimizing the predesigned controller. The advantage of the equivalence is that the predesigned control system needs not to be modified and the incremental attachment can be performed even when the EML system is running. Furthermore, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -learning algorithm is presented for the real-time implementation of the proposed structure and the incrementally attached controller gain system. Finally, the effectiveness of the structure and algorithm is validated on the EML system. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The EML system is key to maglev transportation. It is open-loop unstable, highly dynamic, and its accurate model is generally unavailable. On the other hand, the levitation performance may not be optimal given the predesigned controller. Moreover, during the long-term operation, it is desired in practice that the controller of EML system can be upgraded in a friendly fashion. This article presents a control structure that optimizes the levitation performance in an incremental style, such that the predesigned controller does not need to be modified. The incremental attachment can be realized via the onboard CAN network or UDP channel. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -learning algorithm optimizes the incrementally attached controller gain system without distabilizing the levitation stability of the EML system under the proposed control structure. In such a way, the open-loop and highly dynamic characteristics can be handled and the friendly implementation style can be achieved.

A Ground-Based Electrostatically Suspended Accelerometer.

In this study, we have developed an electrostatically suspended accelerometer (ESA) specifically designed for ground use. To ensure sufficient overload capacity and minimize noise resulting from high suspension voltage, we introduced a proof mass design featuring a hollow, thin-walled cylinder with a thin flange fixed at the center, offering the highest surface-area-to-mass ratio compared to various typical proof mass structures. Preload voltage is directly applied to the proof mass via a golden wire, effectively reducing the maximum supply voltage for suspension. The arrangement of suspension electrodes, offering five degrees of freedom and minimizing cross-talk, was designed to prioritize simplicity and maximize the utilization of electrode area for suspension purposes. The displacement detection and electrostatic suspension force were accurately modeled based on the structure. A controller incorporating an inverse winding mechanism was developed and simulated using Simulink. The simulation results unequivocally demonstrate the successful completion of the stable initial levitation process and suspension under ±1g overload.

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.

Modeling and analysis of a novel 6-DOF magnetic levitation system with experimental verification

To improve the uniformity of magnetic flux and increase the stroke of the magnetic levitation system, this paper designs a novel 6-DOF magnetic levitation system and proposes an improved novel Halbach array. First, a repulsive passive magnetic bearing is utilized to provide levitation force, leading to a noticeable reduction in levitation power consumption. Then, a magnetic circuit model for the magnetic levitation system is established, and the improved novel Halbach array is optimized based on this model. Next, the stable levitation model and measurement model for the system are established, and the magnetic field distribution and magnetic bearing stiffness are analyzed. Results indicated an increase of 0.1[Formula: see text]T in the maximum magnetic flux density, accompanied by an improvement in the uniformity of magnetic flux. Additionally, there is an enhancement of 10% in magnetic bearing stiffness. Finally, a prototype of the system is constructed, and the stable levitation simulation and experiment of the actuator are conducted with this system. The maximum levitation absolute displacement error obtained by simulation is about 655[Formula: see text]nm, and the experimental results exhibited a maximum levitation absolute displacement error of approximately 750 nm for the system, confirming the effectiveness of the proposed modeling method.