• 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.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.253-259
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• 2005

Magnetic encoder with relatively low pulse per rotation is generally used for detecting speed of the high-speed rotating machine. It is due to the fact of the mechanical problems of vibration and bearing stiffness and also the limit of maximum output pulse of the mounted encoder. The magnetic encoder is divided into two types, that is, toothed gear-wheel method and magnetic wheel method according to the shape of the rotation disk. In case of detecting speed by the tooth gear-wheel, the encoder itself can be acted as the additional inertia where the number of tooth determining the output pulse and the width of the wheel detecting the change of the magnetic flux density are relatively enough large considering the volume of the rotating machine. While the magnetic wheel method has the limit of the magnetizing number of the ring magnet, there is relatively few, if nv, the influence of inertia on the machine. In this paper, it is proposed a simple magnetic wheel encoder suited for the high speed rotating machine and the method of signal processing and the output characteristics are examined through the V/F operation of max 48,000(rpm) and 2.4(KW) spindle motor.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.882-887
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• 2011

A spiral electrodynamic wheel is proposed as an actuator for the contactless conveyance of a conductive rod. When rotating the wheel around the rod, a radial force, a tangential force, and an axial force are generated on the rod and cause a screw motion of the rod. The rotation of the rod is the inevitable result due to traction torque of the wheel and the unintended motion to be excluded. However, the rotating speed of the rod should be measured without mechanical contact to be cancelled out through the controller, so the electrodynamic wheel is used as a sensor measuring the rotating speed of the rod indirectly as well as an actuator. In this paper, we model the magnetic forces by the proposed wheel theoretically and compare the derived model with simulation result by Maxwell, and analyze influences on the magnetic forces by key parameters constituting the wheel. The feasibility of the conveyance system is verified experimentally.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.957-965
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• 2011

Recently, railway industry has been developed not only functional parts such as acceleration and high performance of the railway but also emotional parts such as improved ride comfort and blocking noise. However, some important components of railway such as wheel and rail always had exposed too much operation time, cyclic load and rolling contact directly. The variations of load, vibration and chemical compositions were caused of wheel and rail having a lot of different types of contact fatigue damages. Therefore, It is necessary to improve inspection and maintenance technology in order to ensure safety and reliability of railway. Many researchers have already been reported the technology. Magnetic camera, one of the non-destructive testing technique can be used to inspect and evaluate the changes of magnetic field in ferromagnetic and paramagnetic materials with cracks. When an electromagnetic is applied to a specimen, a magnetic field will be distorted around a crack on the specimen. In present paper, the distribution of magnetic property in wheel with cracks using magnetic camera had investigated. The crack can be detected and evaluated by distribution analysis of magnetic field. The magnetic camera technique can be detected and evaluated the crack by rolling contact fatigue.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.72-80
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• 2009

When the magnet wheel rotates over a conducting plate, it generates the traction torque as well as the repulsive force on the conducting plate. Partially-cut traction torque results in the linear force into the tangential direction. To cut the traction torque, the concept of magnetic shield is introduced. The direction change of the linear force is realized varying the shielded area of magnetic field. That is, the tangential direction of non-shielded open area becomes the direction of the linear thrust force. Specially a shape of permanent magnets composing the magnet wheel leads to various pattern of magnetic forces. So, to enlarge the resulting force density and compensate its servo property a few simulations are performed under various conditions such as repeated pattern, pole number, radial width of permanent magnets, including shape of open area. The theoretical model of the magnet wheel is derived using air-gap field analysis of linear induction motor, compared with test result and the sensitivity analysis for its parameter change is performed using common tool; MAXWELL. Using two-axial wheel set-up, the tracking motion is tested for a copper plate with its normal motion constrained and its result is given. In conclusion, it is estimated that the magnet wheel using partial shield can be applied to a noncontact conveyance of the conducting plate.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.795-799
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• 1995

The magnetostriction versus field (${\lambda}-H$) curves for the melt-spun ribbons of $Dy_{x}{(Fe_{1-y}B_{y})}_{1-x}$ (x=0.2, 0.25, 0.3; y=0, 0.05, 0.1, 0.15, 0.2) alloys are measured systematically at various wheel speeds ranging from 10 to 50 m/sec. The ${\lambda}-H$ curves in most cases vary sensitively with the wheel speed and, in the wheel speed range where no amorphous phase is formed, the magnetic softness improves rather continuously with the wheel speed. This result is considered to be due to the reduced grain size with increasing wheel speed, which was confirmed by X-ray diffraction and transmission electron microscopy. In particular, homogeneous and ultrafine grains with size of about 10 nm are formed even in the as-spun state when the $Dy_{0.3}{(Fe_{1-y}B_{y})}_{0.7}$ alloys are quenched at the wheel speed of 30 m/sec (for the alloy with y=0.2) or 40 m/sec (for the alloys with $y{\leq}0.15$) and the ribbons having the nanocrystalline grain structure exhibit good magnetostrictive characteristics.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.923-925
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• 2008

As known generally, when permanent magnets whose poles are upward and downward in order, arranged into the circumferential direction rotate under the conducting plate, the rotating force acts on the plate as well as the repulsive force. If the magnetic field by the magnet wheel(the above rotating permanent magnets) is partially shielded, the magnet wheel over open region can be a linear induction motor. The distinct feature from induction motor is that the traveling magnet field is produced by the moving permanent magnet instead of ac current. Furthermore, a variation of the open region changes the direction of the thrust force. In this paper, we introduce a concept of the linear actuator using the magnet wheel. Under the above shielding condition, a few simulation results and its verification from a simple test setup are described.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.230-236
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• 2012

Shielding the air-gap magnetic field of the electrodynamic wheel below a conductive plate and opening the shielding plate partially, a thrust force and a normal force generate on the conductive plate at the open area. But, as only the variable controlling both forces is a rotating speed of the electrodynamic wheel, it is very difficult to control the forces independently by the speed. So, we discuss a novel method controlling the forces effectively through manipulating a size of the open area. The independent control is made possible by virtue of the feature that the relative ratio between both forces is irrelevant to an air-gap length and determined uniquely for a specific rotating speed of the wheel. Therefore, the rotating speed and the size of open area become new control variables. The feasibility of the method is verified experimentally. Specially, the controllable magnetic forces are used in a noncontact conveyance of the conductive plate.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.600-606
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• 2012

Upon investigation of the damaged wheels for high speed train it was determined that the damage was caused by rolling contact fatigue during operation of train. The major problems that railway vehicle system using wheel-rail has to face during operation of railway vehicle are rolling contact fatigue, cracks in wheels, cracks in rails and wheel-rail profile wear. If these deficiencies are not controlled at early stages the huge economical problems due to unexpected maintenance cost in railway vehicle can be happened. Also, If the accurate knowledge of contact conditions between wheel and rail can be evaluated, the damage of wheel can be prevented and the maintenance operation can save money. This paper presents the applicability of electro-magnetic technique to the detection and sizing of defects in wheel. Under the condition of continuous rolling contact fatigue the damage of wheel has continuously monitored using the applied sensor. It was shown that the usefulness of the applied sensor was verified by twin disc test and the measured damaged sizes showed good agreement with the damaged sizes estimated by electro-magnetic technique.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.793-798
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• 1993

In this study the attitude control of the KOREASAT is investigated. The KOREASAT is a geostationary satellite and its 3 attitude angles, namely, roll, pitch and yaw angles, are stabilized by using the 3-axis stabilization technique. In the pitch control loop, the pitch attitude angle received from the earth sensor is processed in the attitude processing electronics by using PI type control logic, and the control command is sent to the momentum wheel assembly to generate the control torque by varying the wheel rate. The roll/yaw attitude control is performed by activating a magnetic torquer or by firing appropriate thrusters. The magnetic torquer interacts with the earth magnetic field to produce the control torque, and the thrusters are used to control the larger roll attitude errors. In this study dynamic modelling of the satellite is performed. And the earth sensor, the momentum wheel, and the magnetic torquer are mathematically modelled. The 3-axis attitude control logic is implemented to make the closed-loop system and simulations are carried out to verify the implemented control laws.