• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1025-1033
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• 2006

This paper describes the levitation mechanism using magnetic wheel for a maglev planar transportation system. Rotation of the magnetic wheel where the permanent magnet array is embedded produces the time varying traveling magnetic flux density and the generated magnetic flux density creates the induced levitation force and drag force with the conductor. Because the net drag force is zero, magnetic wheel can only generate the levitation force. Thus, it always guarantees the stability in levitation direction and it does not disturb other directional motion. In this paper, levitation principle of the magnetic wheel is analyzed using distributed field approach and dynamic characteristics of the levitation in the magnetic wheel system are estimated. The feasibility of the proposed levitation mechanism is verified through the several experimental works.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.52-56
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• 2022

Single-grain (c-normal or c-parallel) and multi-grain YBCO superconductors were prepared by a melt growth process with/without seeding. The magnetic levitation force and trapped magnetic field at liquid N₂ temperature (77 K) of the YBCO superconductors were investigated. Samples for the levitation force measurement were zero-field cooled (ZFC) to 77 K, and samples for trapped field measurement were field-cooled (FC) using Nd magnets. As for the magnetic levitation force, the c-normal, single grain sample showed the largest value, whereas the multi-grain sample showed the lowest value. The trapped magnetic field of the c-normal and c-parallel single-grain samples was 4-5 times that of the multi-grain sample. In addition, as the external magnetic field (the number of magnets) increased, the both properties increased proportionally. These results were explained in terms of the orientation dependence of the levitation forces and the magnetic field trapping capability of the YBCO superconductor.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.584-592
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• 2008

In this paper, we propose a new model of the magnetic control force exerted on the levitation object in magnetic levitation systems. The model assumes that the magnetic force is a function of the voltage applied to an electromagnet and the position of a levitation object. The function is not explicitly expressed but represented through a 2D lookup table constructed from the experimentally measured data. Unlike the conventional model that reveals only local characteristics of the magnetic force, the proposed model shows global characteristics satisfactorily. Specially devised measurement equipment is utilized in order to gather the data required for model construction. An experimental procedure to construct the model is presented. We apply the proposed model to designing a sliding mode controller for a lab-built magnetic system. The validity of the proposed model is illustrated by comparing the performances of the controller adopting the conventional model with that of the controller adopting the proposed model.

• Tribology and Lubricants
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• v.11 no.1
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• pp.20-26
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• 1995

Most magnetic bearings are based on the attractive force between the magnets and ferrous materials. One of the disadvantages of such attractive type magnetic bearings is the instability so that an active control device is necessary to operate bearing successfully. In this study a repulsive type magnetic bearing is analyzed which uses eddy current as a force source. The load capacities are analyzed for the various gap sizes, the rotor velocities and the frequencies of current supplied to electromagnet. Analytic Results show that as the gap size decreases, the levitation and drag forces increase, while the number of poles increasqs, the drag force decreases in the higher linear velocity region. Experimental results show that as the gap size decreases the levitation and the drag force increase, and as the velocity of rotor increases, the drag is larger than the levitation force up to certain velocity. But after that, the levitation is larger than the drag force. As the frequency of the current increases the levitation and drag decreases while the thickness of rotor gets thicker the forces decrease because of increase in eddy current loss.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2236-2245
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• 2011

This paper deals with the levitation force characteristics of electromagnet for MAGLEV vehicle application. The magnetic flux density distribution and levitation force characteristics of the electromagnet are investigated by means of equivalent magnetic circuit model. Firstly, we defined the aligned and unaligned electromagnet module for the full-electromagnet, and magnetic flux paths are represented for each model including leakage and fringing flux paths. Because of the analysis model contains both the permanent magnet and electromagnet coil, we calculated the airgap magnetic flux density and levitation forces using flux superposition in electromagnetic circuit. The results are validated extensively by comparison with finite element analysis. Moreover, the 1/4 scaled magnetic levitation and propulsion test vehicle has been manufactured and tested in order to verify these predictions. The experimental results confirms the validity of the analytical prediction with equivalent magnetic circuit model for the description of a electromagnet.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.4
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• pp.213-216
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• 2006

The magnetic levitation effect a high Tc superconductor beneath the toroidal permanent magnet was examined by means of a improved magnetic seesaw method. Magnetic effects associated with penetration and pinning in superconductor. One of these was focussing of magnetic field by superconductor and the other was magnetic levitation. The existence of equilibrium was shown to be related to hysteresis observed in the force separation for a toroidal permanent magnet and superconductor. Obtained results indicate that magnetic levitation effect in the present case was mainly due to diamagnetic effect.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.564-569
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• 2012

This paper proposes a hybrid-excited linear synchronous motor (LSM) that has potential applications in a magnetically levitated vehicle. The levitation and thrust force characteristics of the LSM are investigated by means of three-dimensional (3-D) numerical electromagnetic FEM calculations and experimental verification. Compared to a conventional LSM with electromagnets, a hybrid-excited LSM can improve levitation force/weight ratios, and reduce the power consumption of the vehicle. Because the two-dimensional (2-D) FE analysis model describes only the center section of the physical device, it cannot express the complex behavior of leakage flux, which this study is able to predicts along with levitation and thrust force characteristics by 3-D FEM calculations. A static force tester for a hybrid-excited LSM has been manufactured and tested in order to verify these predictions. The experimental results confirm the validity of the 3-D FEM calculation scheme for the description of a hybrid-excited LSM.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.321-327
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• 2011

This paper proposes an equipment and an algorithm for modeling the magnetic force of electromagnets in magnetic levitation systems. We assume that the magnetic force model is represented in terms of a 2D lookup table. The 2D lookup table is constructed by applying noncausal filtering and interpolation to data measured by the proposed modeling equipment. The proposed modeling equipment is designed such that it can measure the magnetic force exerted on the levitation object while it changes the voltage applied to the electromagnet and position of the levitation object. The algorithm of making a 2D lookup table has two stages. The data measured by the proposed modeling equipment is smoothed by a noncausal filter and then the 2D lookup table is obtained by interpolating filtered data. The proposed modeling method has advantages of time-saving, model consistency, and chance of automation for mass production. We show the validity of proposed method through control experiments.

• Tribology and Lubricants
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• v.14 no.4
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• pp.44-50
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• 1998

This paper describes the simulation of the levitation force between permanent magnet and high Tc(critical temperature) superconductor(HTSC). Levitation force is evaluated numerically on the basis of the magnetic vector potential method and the critical state model. The superconductor is approximated to 2-D slab model. By performing computations, the following characteristics have been investigated: the process of the generation of hysteresis, the various hysteretic behaviors. The characteristics of hysteresis are important for the application to magnetic bearing, for the damping and the nonlinear stiffness is related to hysteresis.

• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1643-1651
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• 2002

Magnetic levitation systems are required to have a large operating range in many applications. As one method to solve this problem, Time Delay Control (TDC) is applied to a single-axis magnetic levitation system in this paper A reduced-order observer is utilized to estimate states excluding measurable states in the control law. The system consists of a square air-core solenoid and a circular permanent magnet attached on a plastic ball. Theoretical magnetic forces of the system are obtained on the basis of the location of the magnet around the solenoid. The magnetic levitation force is obtained by the experiment, and then compared with the theoretical one. As the results of the control experiments, the nonlinear controller (TDC : 1-2 ㎜) has a larger operating range than the linear controller (PD control : 1-1.4 ㎜), and is superior to linear. control in the robustness to the modeling uncertainty and the performance of the disturbance rejection.