• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1903-1908
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• 2008

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 한국항공운항학회지
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• 제26권2호
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• pp.47-53
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• 2018

In this paper, we investigate a collision avoidance algorithm for unmanned aerial vehicles using potential field based on the relative velocity of obstacles. The potential field consists of the attraction force and the repulsive force that are generated for the target and the obstacles. And the field can be classified into the attractive potential field generated by the target and the repulsive potential field generated by the obstacle, respectively. In this study, we construct an attractive potential field as a function of the distance between the UAV and the target position. On the other hand, a repulsive potential field is created by a function of distance and the relative velocity of the obstacle with respect to the UAV. The proposed potential field based collision avoidance algorithm is evaluate through simulations.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1202-1208
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• 2006

This paper presents an experimental characteristics of electro-hydraulic proportional pressure control valve. In this study, poppet and valve body which are assembled into the proportional solenoid were designed and manufactured. The constant force characteristics of proportional solenoid actuator in the control region should be independent of the plunger position in order to be used to control the valve position in the fluid flow control system. The stroke-force characteristics of the proportional solenoid actuator is determined by the shape (or parameters) of the control cone. In this paper, steady state and transient characteristics of the solenoid actuator for electro-hydraulic proportional valve are analyzed using finite element method and it is confirmed that the proportional solenoid actuator has a constant attraction force in the control region independently on the stroke position. The effects of the parameters such as control cone length, thickness and taper length are also discussed.

• 한국생산제조학회지
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• 제25권3호
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• pp.157-163
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• 2016

Green vehicles include electric vehicles, natural gas vehicles, fuel cell vehicles (FCV), and vehicles running on fuel such as a biodiesel or an ethanol blend. An FCV is equipped with a cylinder valve installed in an ultra-high pressure vessel to control the hydrogen flow. For this purpose, an optimum design of the solenoid actuator is necessary to ensure reliability when driving an FCV. In this study, an electromagnetic field analysis for ensuring reliable operation of the solenoid actuator was conducted by using Maxwell V15. The electromagnetic field analysis was performed by magnetostatic technique, according to the distance between magnetic poles in order to predict the attraction force. Finally, the attraction force was validated through comparison between the Maxwell results and measurement results. From the results, the error of attraction force ranged from 4.53 % to 9.05 % at testing conditions.

• 한국기계가공학회지
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• 제15권2호
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• pp.89-96
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• 2016

Growing concerns regarding environmental pollution have increased the demand for green vehicles. Green vehicles include electric vehicles, compressed natural gas vehicles, fuel cell vehicles, and vehicles running on fuels such as bio diesel or an ethanol blend. CNG vehicles are equipped with a cylinder valve installed in a high-pressure vessel to control the CNG flow. For this purpose, the optimum design of cylinder valve solenoid is necessary to secure at driving a CNG vehicle. In this study, electromagnetic field analysis to ensure the reliable operation of the solenoid was conducted by using a Maxwell V15. The electromagnetic field analysis was performed by magnetostatic technique according to distance between magnetic poles in order to predict the attraction force. Finally, the attraction force was validated through comparison between the Maxwell results and the measurement results. From the results, the error of attraction force was found to be 2.85 N to 6.5 N under the testing conditions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1610-1615
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• 2007

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 유공압시스템학회논문집
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• 제2권3호
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• pp.1-5
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• 2005

There are two types of solenoid actuator for force and position control of the fluid power system. One is an on-off solenoid actuator and the other is an electro-magnetic proportional actuator. They have some different characteristics for attraction force according to solenoid shape. Attraction force of the on-off solenoid actuator only depends on flux density. And the stroke-force characteristics of the proportional solenoid actuator are determined by the shape of the control cone. In this paper, steady state characteristics of the solenoid actuator for electro-hydraulic proportional valve determined by the shape of control cone are analyzed using finite element method and it is confirmed that the proportional solenoid actuator has a constant attractive force in the control region independently on the stroke position. And the shape of control cone is optimized using 1+1 evolution strategy to get a constant force. In the optimization algorithm, control cone length, thickness and taper length are used as a design parameter.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.103-112
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• 2021

The labor force plays an important role in attracting foreign direct investment (FDI) both in developed and developing countries. In countries where there are appropriate policies for training human resources and maintaining the health of human resources, such countries have a competitive advantage and can attract FDI inflows, besides having a workforce to meet the needs of foreign investors. The purpose of this paper is to analyze the effect of the labor force and several other factors on FDI attraction in Vietnam. The empirical model is employed to perform regression and correlation on the impact of the labor force, real gross domestic product, inflation, index of business freedom, and index of investment freedom on Vietnam's FDI attraction by using a secondary time series data set during the period 1995-2018. The empirical results found that both labor force and inflation have a positive influence on FDI at a 5% significance level; index of business freedom has a positive impact on FDI at a 10% significance level, and real gross domestic product and index of investment freedom have a positive impact on FDI at a 1% significance level. From these results, this study proposes several important policy implications for Vietnam in attracting FDI in the future.

• 한국자기학회지
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• 제6권1호
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• pp.40-47
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• 1996

본 논문에서는 영전식 magnetic lifter의 최적 설계 방법을 제시하였다. 등가 자기회로법으로 흡착시와 탈착시의 자장 해석 및 전자역 계산을 행하였고, 최적 설계를 위해 등가 자기회로법으로 해석된 흡착시의 전자력을 최대로 하는 lifter의 치수를 구하였다. 또한 흡착시의 전자력을 제한 조건으로 하여 lifter 전체의 부피를 최소로 하는 치수를 찾았다. 위 최적 설계를 위한 최적화 알고리즘으로는 (1+1) Evolution Strategy(ES)를 이용하였다. 또한 상용 자장해석 프로그램(MAXWELL)을 사용하여 얻은 결과와 위의 최적화 결과를 비교하여 본 논문의 최적화방법의 타당성을 검증하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권2호
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• pp.77-83
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• 2000

This paper deals with the design of a touch free eddy-current brake for high speed transportation systems by using 2-dimensional Finite Element Method (2-D FEM). The eddy current brake systems have to equipped with maximum braking force and deceleration at the given volume or mass, high braking force at small rate, attraction forces as small as possible and stable construction. The parameters, such as the number of pole, electric ampere-turns and slot width have influence on these braking characteristics. For the magnet to satisfy above-mentioned performance in high speed, the braking performance according to variation of the parameters are analyzed by the 2-D FEM. In addition, the magnet stack width is determined from equivalent stack width that is calculated by solution of the Field with scalar potential. From these results, the magnet of optimized configuration with maximum braking force and minimum attraction force is designed by the process of detail design.