• 한국산업융합학회 논문집
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• 제26권2_1호
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• pp.231-238
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• 2023

This paper develops the theory for a novel fault-tolerant, permanent magnet biased, 6-active-pole, homopolar magnetic bearing. The Lagrange Multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrices for the failed bearing. some numerical examples of distribution matrices are provided to illustrate the new theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events (up to any combination of 3 coils failed for the 6 pole magnetic bearing) while currents and fluxes change significantly. The overall load capacity of the bearing actuator is reduced as coils fail. The same magnetic forces are then preserved up to the load capacity of the failed bearing.

• 한국정밀공학회지
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• 제15권11호
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• pp.199-207
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• 1998

This paper presents the design and the control of three degree-of-freedom(DOF) fine positioning device based on an electro-magnetic force. The device is designed by use of a magnetic circuit theory and it is capable of fine motion due to the electro-magnetic force. The device consists of permanent magnets, yokes and coils. The magnetic fluxes generated from the permanent magnets constitute magnetic paths through steel, whereas the coils are arranged into the gap between two surfaces of the yokes. Therefore, by supplying current to the coils, the coils are capable of some motions due to Lorentz forces. For the optimal design of the actuating system, the system parameters are defined and investigated under the given constraints. From the system modeling in small displacement, three decoupled equations of motion are obtained. To get better performance of the system, a PID controller is implemented. Experimental results are presented in terms of time response and accuracy.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.82-87
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• 2007

A Halbach array is a special arrangement of permanent magnets which augments the magnetic field on one side of the device while cancelling the field to near zero on the other side. The application of this Halbach array magnet to the electrodynamic suspension for Maglev train has been recently studied in order to increase the levitation capability. This paper is focused on analytical method of the magnetic levitation system using Halbach array magnet. The suitability of the proposed method is verified with comparing to a finite element method. From this study, it is confirmed that the proposed method provides a reasonable solution with a little analysis time to the finite element method and the magnetic levitation system using Halbach array magnet is stable dynamically.

• 대한기계학회논문집A
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• 제32권8호
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• pp.654-659
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• 2008

This paper is to suggest a concept design of the permanent magnet type magnetic resonance imaging (MRI) device based on the parameter optimization method. Pulse currents in the gradient coils will introduce the effect of eddy currents in the ferromagnetic material, which will worsen the quality of imaging. In order to equalize the magnetic flux in the MRI device for good imaging, the eddy current effect in the ferromagnetic material must be taken into account. This study attempts to use the design of experiment (DOE) and the response surface method (RSM) for equalizing the magnetic flux of the permanent magnet type MRI device using that the magnetic flux can be calculated directly using a commercial finite element analysis package. As a result, optimal shapes of the pole and the yoke of the PM type MRI device can be obtained. The commercial package, ANSYS, is used for analyzing the magnetic field problem and obtaining the resultant magnetic flux.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.218-223
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• 1993

In this paper, we present a full digital control scheme which controls currents and speed of the permanent magnet AC servo motor with large range of bandwidth and high performance. The current equations of the permanent magnet AC servo motor are linearized by feedback linearization technique. Both acceleration feedforward terms and IP controllers, whose gains are functions of motor speed, are used in order to control motor currents. In addition the phase delays in current control loops are compensated by placing phase lead-lag compensators after current commands, which make it possible to avoid high gains in the current controllers. Unity power factor can be achieved by the proposed current controller. Pulsewidth modulation is performed by way of the well-known comparison with a triangular carrier signals. The velocity controller is designed on the basis of the linearized model of the permanent magnet AC servo motor by the proposed current controller. The performance of the entire control system is analyzed in the presence of uncertainty in the motor parameters. The proposed control scheme is implemented using the digital signal processor-based controller composed of an Analog Device ADSP 2111 and a NEC78310. The pulsewidth modulation (PWM) signals are generated through a custom IC, SAMSUNG-PWM1, which has the outputs of current controllers as input. The experimental results show that the permanent magnet AC servo motor can be always driven with high dynamic performance by the proposed full digital control scheme of motor speed and motor current.

• 한국정밀공학회지
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• 제17권10호
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• pp.69-76
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• 2000

Lots of semi-active control devices have been developed in recent years because they have the best features of passive and active system. Especially, controllable magneto-rheological(MR) fluid devices have received significant attention in these area of research. The MR fluid is the material that reversibly changes from a free-flowing, linear viscous fluid to a semisolid with a controllable yield strength in milliseconds when exposed to a magnetic field. If the magnetic field is induced by moving a permanent magnet instead of applying current to a solenoid, it is possible to design a MR damper consuming low power because the power consumption is reduced at steady state. This paper proposes valve mode MR damper using permanent magnetic circuit that has wide range of operation with low power consumption, a design parameter is adopted. The magnetic circuit, material of choke and choke type are selected experimentally with the design parameter. The behaviors of the damper are examined and torque tracking control using PID feedback controller is performed for step, ramp and sinusoidal trajectiories.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.433-439
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• 2000

Lots of semi-active control devices have been developed in recent years because they have the best features of passive and active system. Especially, controllable magneto-rheological(MR) fluid devices have received significant attention in these area of research. The MR fluid is the material that reversibly changes from a free-flowing, linear viscous fluid to a semisolid with a controllable yield strength in milliseconds when exposed to a magnetic field. If the magnetic field is induced by moving a permanent magnet instead of applying current to a solenoid, it is possible to design a MR damper consuming low power because the power consumption is reduced at steady state. This paper proposes valve mode MR damper using permanent magnetic circuit that has wide range of operation with low power consumption and small size. To design a MR damper that has a large maximum dissipating torque and a low damping coefficient, a design parameter is adopted. The magnetic circuit, material of choke and choke type are selected experimentally with the design parameter. The behaviors of the damper are examined and torque tracking control using PID feedback controller is performed for step, ramp and sinusoidal trajectories.

• 한국자기학회지
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• 제9권1호
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• pp.48-54
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• 1999

자기부상형 리니어 모터와 비접촉 구동에 의한 크린룸 환경용 물류 운송장치를 개발하기 위하여 접촉 없이 완전하게 부상되는 자기부상레일을 개발하고자 하였다. 영구자석의 같은 극을 마주보게 배치할 때 생성되는 작용력에 의한 부상 특성을 파악하고, 해석을 통하여 외력 변화에 강인하고 부상위치의 변화가 작은 반발부상형 레일을 설계·제작하였다. 개발된 부상 레일은 고정자석 양면에서 서로 반발되게 자석을 배열하여 부상하는 구조로 상호 반발력에 의하여 평형이 이루어지기 때문에 부상체에는 횡력만 작용하게 된다. 부상계에서 발생되는 횡력은 부상체의 부상 중심 위치에 반발력을 이용한 보조자석을 설치하여 제어하고자 하였다.

• 전기학회논문지
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• 제63권3호
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• pp.431-436
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• 2014

In this paper, temperature change properties on the 210kW-class Interior Permanent Magnet Synchronous Motor (IPMSM) are performed with the cooling performance of a water cooling device through the thermal characteristic analysis of the IPMSM considering a real driving pattern of urban railway vehicles. First, the thermal analysis modeling of 210kW-class IPMSM, which is an alternative to the conventional induction motor, and its water cooling device is conducted. Next, the thermal characteristic analysis of the IPMSM considering a real driving pattern of urban railway vehicles is performed using 2-Dimensional FEM tool. Finally, the calculated characteristic results are analyzed. Consequently, it is confirmed that the internal temperature of the 210kW-class IPMSM may be lowered to about 42~52% by maintaining the coolant flow rate of the water cooling device (Cross sectional shape of the pipe has 220mm width and 10mm height) for 0.2kg/s level.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.73-75
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• 2002

Single phase SRM(switched reluctance motor) is very simple in structure and in driving circuit than three phase SRM. But it can't be started by itself. The prototype of salient pole rotor type single phase SRM was fabricated in former research and the starting device was installed in bottom of the rotor for generating start torque. The starting device is composed of permanent magnet and it is placed the rotor at specific position which is generated positive torque when the prototype is started. Therefore the prototype was started by itself but it is also affected the torque and the speed in operation. On this paper, the influence of the starting device on no-load speed of the prototype was confirmed by measurement of no-load speed according to installation of the starting device or not.