Electromagnetic Levitation System Research Articles

Design of a coil for electromagnetic levitation: comparison of numerical models and coil realization

Electromagnetic levitation is a unique environment allowing for making non-contact measurements over samples of liquid metals at different temperatures. The electromagnetic coil is the core of the electromagnetic levitation system, and its design defines the amount of energy introduced into the sample as well as the shape and stability of the latter during levitation. In the present work, analytical and numerical modelling for a real electromagnetic inductor is performed and compared with experimental observations. The shape of the experimental electromagnetic coil is assured due to 3D printing of a template which is used for the coil winding. Tables 3, Figs 5, Refs 14.

Reinforcement Learning-Based Optimal Tracking Control for Levitation System of Maglev Vehicle With Input Time Delay

The running environment of a magnetic levitation (maglev) vehicle is complex, with problems such as track irregularity, external disturbance, varying system parameters, and time delays, which bring great challenges to the design of a high-performance levitation controller. In this article, an adaptive neural network controller with input delay compensation and a control parameter optimization scheme is proposed for the electromagnetic levitation system of a maglev vehicle, which can solve the key engineering problems of external disturbance, input time delay, and time-varying mass. Aiming at the problem of input time delay, a sliding-mode surface with time-delay compensation is constructed, and a double-layer neural network and adaptive law are utilized to approximate the uncertain dynamics; thus, a finite time adaptive tracking control law is proposed. Based on the Lyapunov method, the stability of the proposed controller in finite time is analyzed. The proposed method does not only update the input and output weights of the neural network online, but also introduces reinforcement learning (Actor–Critic network) to optimize the key controller parameter in real time and enhance system robustness. Simulation and experimental results show that the proposed controller can effectively suppress the air gap vibration with time delay and uncertain dynamics, and significantly improve the performance of levitation control.

Influence of eddy effect of coils on convection and deformation of electromagnetically levitated droplet

This paper presents a comparative modeling of free surface deformation, fluid flow, and temperature distribution in electromagnetically levitated molten droplets with and without the eddy effect of coils in both normal and microgravity environments. The results show that in the TEMPUS device (Tiegelfreies ElektroMagnetisches Prozessieren Unter Schwerelosigkeit), a dual-frequency electromagnetic levitation system in microgravity, the alternating currents in the positioning and heating coils function as a reciprocal load owing to the mutual inductance, which leads to a visible decline in the induced current in the droplet. Consequently, the temperature level and deformation of the droplet were dramatically overestimated after the eddy effect was omitted. Under terrestrial conditions, the alternating currents in the lower and upper coils have the same frequency and magnitude but run in opposite directions. The major influence of the omitted eddy effect is the enhanced equilibrium position of the droplet, whereas the influence on convection and the temperature field is minimal. With this work, it is expected that the behaviors of electromagnetically levitated droplets can be predicted more precisely by considering the eddy effect of coils for a better understanding of the convection, temperature distribution, and deformation of the droplet.

In-situ observation of S/L interface migration and mechanical property increase of Inconel 600 alloy prepared by electromagnetic levitation

The Inconel 600 alloy was highly undercooled and its S/L interface migration during recalescence was observed in real time by using the electromagnetic levitation (EML) system. The characteristic of S/L interface migration and the dendritic growth velocity are strongly dependent on undercooling. At a small undercooling, the γ phase nucleates and grows to the undercooled melt with a sharp interface, and the corresponding microstructure appears as dendrite with strong texture. Nevertheless, once the undercooling exceeds the critical undercooling the sharp S/L interface transforms to a planar shape, which is attributed to the formation of equiaxed grain with a diffused orientation distribution. The 60°<111> annealing twins are generated only when the undercooling is larger than 130 K, due to the obvious recrystallization and sufficient driving force. Besides, the compressive tests were performed on the bulk Inconel 600 alloy samples. The results demonstrate that the elastic modulus is affected little by the undercooling, however, the yield strength obviously increases with the enhancement of undercooling. The strengthening mechanism is mainly ascribed to the formation of sub grain boundaries and annealing twins.

Simulation and Test of Energy Consumption of High-Tc Superconducting Coils in Electromagnetic Levitation System

In order to evaluate the energy consumption of the superconducting magnetic levitation system with real-time control, the methods of simulation and test were used to study the AC plus DC loss of the superconducting coil. The simulation established a 2D finite element model in COMSOL, which was based on the H equations method with simple form and fast calculation speed. The test was carried out on a new type of measurement system, which adopted the electrical method with high sensitivity, simple operation and easy implementation. The results of simulation and test showed that, under normal working conditions, the levitation current in the form of AC plus DC produced a relatively small energy loss below $1mW$ per meter. This conclusion is helpful for the promotion and application of superconducting magnetic levitation control system.

Silicate Island Formation in Gas Metal Arc Welding

Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.

Mass estimation and adaptive output feedback control of nonlinear electromagnetic levitation system

Electromagnetic levitation system (EMS) has inherently unstable dynamics and is strongly nonlinear in nature. In this paper, feedback linearization controller is utilized for stabilization and trajectory tracking of the EMS. Then, Linear Quadratic Regulator (LQR) approach is used to determine the gains of mentioned controller, which enables us to minimize the combination of the state error and control effort. As all measurements of the EMS states are not accessible, a nonlinear observer is utilized to estimate the unmeasured states. On the other hand, the EMS has a model uncertainty originated from the unknown carriage weight. To deal with these issues, nonlinear versions of Kalman filter have been used to simultaneously estimate states and parameter (carriage mass) of the EMS. Simulations are conducted on the EMS and compared to the existing results in the literature to appraise the overall performance of the proposed method. The evaluation of simulation results demonstrates that the proposed control methodology is efficient not only in stabilizing the levitated object but also in attenuating the disturbance and uncertainty present in the EMS.

Vertical Dynamic Response Prediction of the Electromagnetic Levitation Systems

Due to the limited deviation range of the controllable levitation gap, the vehicle/track coupling dynamic problem of the maglev transportation system is very prominent. The stability of the electromagnetic levitation system is deeply affected by the track irregularity. It is found that there are obvious dynamic characteristic differences of the electromagnetic levitation system, and the deviation range of the levitation gap increases gradually with the increase of the train speed. This paper presents a vertical dynamics prediction method of the electromagnetic levitation system. Firstly, the model of the electromagnet module and the track is established. Then, the amplitude spectrum functions of the levitation gaps are obtained by using the discrete frequency excitation method. Based on the amplitude spectrum functions, the vertical dynamic response of the levitation system can be predicted. The amplitude spectral analysis results are consistent with the numerical simulation results.

Investigation on planar electromagnetic levitation system using lead compensation and LQR controllers

Magnetic levitation is a method by which an object is suspended with no support other than magnetic fields. The main objective of this study is to demonstrate stabilized closed-loop control of 2-DOF maglev experimentally using real-time control Simulink feature of (SIMLAB) microcontroller. Phase lead compensation and linear quadratic regulator (LQR) controllers are employed to examine the stability performance of the maglev control system under effect of sudden wave signal change and load on maglev plane. The effect of sudden change of applied wave signal on single point, line and plane is presented. Furthermore, in order to study the effect of sudden change of applied load, the direct full load has been applied on all points of the prototype maglev plate simultaneously. Moreover, the airgap distance controlled using phase lead compensation controller is unstable with high oscillation. Meanwhile, LQR controller provided more stability, homogeneous response and good agreement. Additionally, the results of pulse width modulation reveal that the control system using LQR controller provides identical and smooth response to adjust the levitated plane compared to phase lead compensation controller.

Hybrid intelligent controller design for an unstable Electromagnetic Levitation System: A fuzzy interpolative controller approach

This article presents the design and implementation of hybrid intelligent controller for the dynamically nonlinear and unstable electromagnetic levitation system (EMLS). The hybrid design is having the intelligence of the fuzzy interpolative controller (FIC) with estimation ability and noise immunity achieved by means of the Kalman filter. The fuzzy inference system (FIS) is replaced by fuzzy linear interpolation networks based on look-up table to form the fuzzy rule base in ordered to reduce the computational complexity and to boost up the execution speed of the control approach as compared to conventional Mamdani or Sugeno type FIS toolkits. The proposed design stabilises the EMLS under wide initial and assorted operating conditions. Further, the proposed controller maintains the performance robustness under 0-25% of vertical payload disturbance by holding the steel ball within the safe limits. Simulation results are presented to validate the novelty and effectiveness of the proposed approach for EMLS.

Dynamic Performance Optimization of Electromagnetic Levitation System Considering Sensor Position

The controlled air gap of the electromagnetic levitation system of maglev train is generally 8-10mm, which makes the vehicle/guideway coupling problem prominent. In practice, it is found that the stability of the magnetic levitation system is affected by guideway irregularities, and the levitation gaps show different dynamic characteristics, which is closely related to the sensor positions. The purpose of optimization of the dynamic performance of the electromagnetic levitation system is to reduce the dynamic deviation amplitude of the levitation gaps. Firstly, a linear model of the module levitation system with guideway is proposed. On this basis, the discrete frequency excitation method is used to obtain the dynamic amplitude response of the levitation gaps at different guideway wavelengths and vehicle speeds. Then, an optimization framework based on sensor positions is proposed. Based on this framework, the optimal sensor position at different speeds is obtained. The simulation results show that the optimal scheme can effectively reduce the deviation amplitude and the difference between the two levitation gaps, thus improving the dynamic performances of the electromagnetic levitation system.

A basic study on levitation characteristics of metal foil by edge-supported electromagnetic levitation system

The grasping and conveying of an object by utilizing the frictional force generated by contact are performed during various steps in the process of manufacturing industrial products. Deterioration of the surface quality due to these contacts is a problem. A noncontact way to transport steel plates using electromagnetic force has been proposed as a solution to these problems. In such applications to date, electromagnets are installed in the vertical direction. However, if the steel plate is thin and lacks sufficient flexural rigidity, it is difficult to exert enough suspension force to levitate the entire steel plate. To solve this problem, we propose an edge-supported electromagnetic levitation system suitable for flexible steel plates using electromagnets installed in the horizontal direction. In this paper, we report on levitation experiments to verify the effectiveness of the proposed system and discuss characteristics of the horizontal positioning of electromagnets and levitation suspension.

Basic study on effect of transport acceleration in electromagnetic levitation system for thin steel plate

Thin steel plates are widely used in various industrial products. However, because of the deterioration of surface quality and metal plating that occurs during transport, some problems exist. As a solution to these problems, a noncontact transport of steel plate using electromagnetic force has been proposed. However, side slip or the dropping of the plate may occur. Therefore, we proposed the addition of electromagnetic actuators to control the horizontal motion of levitated steel plates. In this study, we examined the change in the levitation stability during noncontact transport with the addition of positioning control in the horizontal direction or changed transport conditions. As a result, the application of a magnetic field in the horizontal direction improved the levitation stability of transported thin steel plates in different transport conditions.

Vibration suppression effect in an electromagnetic levitation system for flexible steel plate: experimental consideration on levitation performance using sliding mode control

Vibration suppression effect in an electromagnetic levitation system for flexible steel plate: experimental consideration on levitation performance using sliding mode control

Force Sensor Model Based on FEA for the Electromagnetic Levitation System

The traditional control strategy of the electromagnetic levitation system (ELS) is a voltage or current control strategy based on the gap sensor and the current sensor. In this paper, an electromagnetic force sensor model is proposed and the mapping relation between electromagnetic force with current and levitation gap is obtained by Maxwell computation. The new force sensor model is used in ELS's control simulation and the result shows a new force sensor model can work well.

Numerical Investigation of the Position and Asymmetric Deformation of a Molten Droplet in the Electromagnetic Levitation System

In this study, a numerical model was developed of the electromagnetic levitation system based on the actual structure and size of the levitation coil. The model was then used to investigate the effects of the induced magnetic field, the electric field, and the magnetic force on the lateral drift and irregular deformation of different sized copper droplets. In addition, several tests were conducted in order to verify the conclusions obtained from the numerical simulation analysis.

Design and experiment of an electromagnetic levitation system for a micro mirror

In this paper, the design and characterization of a contactless electromagnetic levitation and electrostatic driven microsystem is presented, which has applications for example for large scale angle rotation micro mirrors. The proposed design can levitate a fabricated aluminum micro rotor which can incorporate a mirror and control it to rotate around the vertical axis within the range of ± 180°, which enlarges the scanning angle dramatically compared with conventional torsion micro mirrors. The rotation angle of the micro rotor is detected by the change of capacitance and controlled by the electrostatic force produced by variable capacitors. The levitation of the micro rotor is realized by utilizing electromagnetic inductions. The rotation is achieved through electrostatic forces generated by a digital controller. The hybrid system design for a micro rotor, combining magnetic and electrostatic forces is introduced. The digital control strategy is based on a PID controller with bias voltage. The detection interface circuit, which is based on frequency multiplexing, is also presented in this paper. It has been experimentally shown that the proposed design can levitate a 1.65 mm radius and 8 µm thickness aluminum micro rotor to 100 µm height with 20 MHz frequency and 0.5A p-p input current. Square and slope wave input experiments were carried out. The experimental results show that the control principal is in good agreement with the simulation models and this applies as well to the time-response performance and stability.

Basic study on edge supported electromagnetic levitation system for flexible steel plate

Basic study on edge supported electromagnetic levitation system for flexible steel plate

Takagi-Sugeno fuzzy regulator design for nonlinear and unstable systems using negative absolute eigenvalue approach

This paper introduces a Takagi-Sugeno &#x0028 T-S &#x0029 fuzzy regulator design using the negative absolute eigenvalue &#x0028 NAE &#x0029 approach for a class of nonlinear and unstable systems. The open-loop system is initially embodied by the traditional T-S fuzzy model and then, all closed-loop subsystems are combined using the proposed Max-Min operator &#x0028 discussed in Section III &#x0029 in place of traditional weighted average operator from the controller side to lessen the coupling virtually and simplify the proposed regulator design. For each virtually decoupled closedloop subsystem, the composite regulators &#x0028 i.e., primary and secondary regulators &#x0029 are designed by the NAE approach based on the enhanced eigenvalue analysis. The Lyapunov function is utilized to guarantee the asymptotic stability of the overall T-S fuzzy control system. The most popular and widely used nonlinear and unstable systems like the electromagnetic levitation system &#x0028 EMLS &#x0029 and the inverted cart pendulum &#x0028 ICP &#x0029 are simulated for the wide range of the initial conditions and the enormous variation in the disturbance. The transient and steadystate performance of the considered systems using the proposed design are analyzed in terms of the decay rate, settling time and integral errors as IAE, ISE, ITAE, and ITSE to validate the effectiveness of the proposed approach compared to the most popular and traditional parallel distributed compensation &#x0028 PDC &#x0029 approach.

A CFD Study Assisted with Experimental Confirmation for Liquid Shape Control of Electromagnetically Levitated Bulk Materials

Two types of optimized electromagnetic levitators were designed to achieve the free surface shape control of metallic melts as the combined results of the Lorentz force, sample gravity, and surface tension. The levitation behavior of bulk melts was investigated using computational fluid dynamics (CFD) modeling coupled with high-frequency electromagnetic field analysis and the arbitrary Lagrangian–Eulerian (ALE) method. The difference in the oscillation behavior between the solid and molten samples was explained by the damping of the electromagnetic induction and liquid viscosity. The motion of the mass center, melt shape, flow pattern, and Lorentz force in the levitated melt were determined within a wide excitation current range. With the increase in the applied current, the melt’s centroid position rose sharply in the area with low current but displayed a slow increase in the area with high current. Meanwhile, the stable shape of the bulk melt showed the typical transition from a long taper through a short taper and then into a rhombus. The internal flow pattern transformed from a simple double-loop structure to a complex configuration with three or four loops. The dependence of the deformation on the Bond number was analyzed in the two types of levitators. In addition, the stable shape and swing process of the bulk Al melt within the two types of electromagnetic levitation (EML) systems were quantitatively studied under protective inert gas conditions. The melt contour could be well described by the 10th Legendre polynomial function with a deviation of less than 0.5 pct.