• 한국산학기술학회논문지
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• 제20권12호
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• pp.797-803
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• 2019

본 연구는 동력분산형 고속열차의 횡방향 진동을 저감하기 위하여 진행되었다. 동역학 해석을 통한 연구에서 동력분산형 고속열차 시제차량(HEMU-430X)은 고속열차에서 주로 사용되는 차륜프로파일(XP55, GV40, S1002)에 관계없이 낮은 등가답면구배에서 횡방향 진동이 커지고, 차륜 마모가 진행되어 등가답면구배가 커지면 횡진동이 감소하는 경향을 보였다. 이는 HEMU-430X에 적용된 현가장치 특성치들의 조합된 결과로 인해 등가답면구배가 낮을 때 차체와 대차가 1.4Hz의 주파수로 공진하여 차체 헌팅이 발생되기 때문이다. 고속열차의 횡방향 진동저감에 대한 해외 사례에서 요댐퍼의 유압강성(Hydraulic stiffness)을 낮추어 진동을 개선한 사례를 고찰하였다. 요댐퍼의 시리즈 강성은 유압강성과 탄성조인트의 조합인데 본 연구에서는 유압강성 조정대신 비교적 간단하게 할 수 있는 탄성조인트의 강성을 낮추어 횡방향 진동을 개선하고자 하였다. 신규 제작된 탄성조인트를 적용한 요댐퍼의 시리즈 강성은 기존 요댐퍼 대비 60% 수준으로 낮았다. 60% 수준의 시리즈 강성이 적용된 요댐퍼를 HEMU-430X의 TC~M2 3량에 설치하여 시운전 시험을 수행하였다. 시운전 시험 결과 TC를 선두로 한 하행 주행 시 TC~M1의 횡방향 진동이 개선되고, MC를 선두로 한 상행 주행 시 후미 TC차량의 횡진동이 개선되는 결과를 보였다. 본 연구의 진동저감 방안은 향후 영업운전을 위해 도입되는 EMU-250 및 EMU-320의 횡방향 진동 문제 발생 시 해결책으로 적용할 수 있다.

• Design & Manufacturing
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• 제1권1호
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• pp.7-11
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• 2007

The fabrication of precision optical components by deterministic CNC grinding is an area of great current interest. Replacement of the traditional, craftsman driven, optical fabrication process is essential to reduce costs and increase process flexibility and reliability. Moreover, CNC grinding is well suited to the fabrication of complex shapes such as aspheres, making it possible to design optical systems with fewer components and reduced weight. Current technology is capable of producing surfaces with less than 2 microns peak to valley error, 50 nm rms surface roughness, and less than 1 micron subsurface damage. Bound abrasive tools, in which the abrasive particles are fixed in a second (matrix) material, play an important part in achieving this performance. In this paper, the factors affecting the ultra-fine surface roughness and profile accuracy of machined surfaces of aspheric parts has been analyzed experimentally and theoretically and on ultra-precision aspheric grinding system and precise adjusting mechanism have been designed and manufactured. In the paper we report the results of experiments and modeling performed to examine the effects of machinability, occurring during grinding of optical surfaces, on the tool surface profile. Profiles of machined surface were measured by using SEM. In order to optimize grinding conditions of aspheric lens processing, we performed experiments by design of experiments.

• International Journal of Railway
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• 제2권2호
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• pp.43-49
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• 2009

Wear and rolling contact fatigue (RCF) defects are most important causes of rail damage, and often interaction competitive at present railway track. Head check is one of rolling contact fatigue (RCF) defects, and generally occurs in mild circular curves and transition curves that are set at both ends of sharp circular curves. Wear tends to limit the crack growth of head checks by removing the material from the RCF surface. In order to clarify the conditions of the occurrence and growth of head checks, the authors measured the interacting forces between wheels and rails and the angle of attack of wheelset, and carried out contact analyses using the actual profile data of wheels and rails. The effects of the lateral force, the contact geometry, and the wear rate at rail gauge comer on the formation of head checks were also analyzed by using the worn profiles of actual wheels and rails and the data obtained by a track inspection car. Some specific range of wear rate at the gauge comer was identified as having close relation with occurrence of head checks.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.75-80
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• 2011

In the area of wheel on rail vehicle, hunting stability which is generated by lateral motion is one of important characteristics for running safety. It might cause not only oscillation of vehicle but also derailment in an unstable area of the high speed. A Maglev vehicle is usually controlled the voltage to maintain the air gap between electromagnet and track. However, in Maglev system, an occurrence possibility of hunting motion could be high, because Maglev vehicle is not controlled directly lateral force between electromagnet and track in the curved guideway. In this paper, running safety is evaluated when Maglev vehicle run on guideway at high speed according to installment of damper between maglev vehicles and bogies, and to analyze the effect of it. Also, the parametric study is carried out for selecting effective lateral damper properties through the simulation. To accurately predict the running safety, 3d multibody dynamics models which are included air spring, guideway conditions and irregularities profile are used. With the results acquired, suggestions were made whether to adopt the damper and how to optimize the damping characteristics.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1431-1438
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• 2013

A pack-level battery hardware-in-the-loop simulation (B-HILS) platform is implemented. It consists of dynamic vehicle models using PSAT and multiple control interfaces including real-time 3D driving and GPS mode. In real-time 3D driving mode, user can drive a virtual vehicle using actual drive equipment such as steering wheel and accelerator to generate the cycle profile of the battery. In GPS mode, actual road traffic and terrain effects can be simulated using GPS data while the trajectory is displayed on Google map. In the latter part of the paper, several performance tests of an actual lithium-polymer battery pack are carried out utilizing the developed system. All experiments are conducted as parts of actual development process of a commercial battery pack adopting 2nd generation Prius as a target vehicle model. Through the experiments, the low temperature performance and fuel efficiency of the battery are quantitatively investigated in comparison with the original nickel-metal hydride (NiMH) pack of the Prius.

• Journal of Biosystems Engineering
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• 제33권5호
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• pp.355-361
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• 2008

As agricultural machinery has become larger and tillage practices have changed in recent decades, compaction as a result of wheel traffic and tillage has caused increasing concern. If strategies to manage compaction, such as deep tillage, could be applied only where needed, economic and environmental benefits would result. For such site-specific compaction management to occur, compacted areas within fields must be efficiently sensed and mapped. We previously developed an on-the-go soil strength profile sensor (SSPS) for this purpose. The SSPS measures within-field variability in soil strength at five soil depths up to 50 cm. Determining the variability structure of SSPS data is needed for site-specific field management since the variability structure determines the required intensity of data collection and is related to the delineation of compaction management zones. In this paper, soil bin data were analyzed by a spectral analysis technique to determine the variability structure of the SSPS data, and to investigate causes and implications of this variability. In the soil bin, we observed a repeating pattern due to soil fracture with an approximate 12- to 19-cm period, especially at the 10-cm depth, possibly due to cyclic development of soil fracture on this interval. These findings will facilitate interpretation of soil strength data and enhance application of the SSPS.

• 한국분무공학회지
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• 제27권3호
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• pp.155-160
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• 2022

Recently, major developed countries have strengthened automobile fuel efficiency regulations and carbon dioxide emission allowance standards to curb climate change caused by global warming worldwide. Accordingly, research and manufacturing on electric vehicles that do not emit pollutants during actual driving on the road are being conducted. Several automobile companies are producing and testing electric vehicles to commercialize them, but it takes a lot of manpower and time to test and evaluate mass-produced electric vehicles with driving mileage of more than 300km on a per-charge. Therefore, in order to reduce this, a simulation model was developed in this study. This study used vehicle information and MCT speed profile of small electric vehicle as basic data. It was developed by applying Simulink, which models the system in a block diagram method using MATLAB software. Based on the vehicle dynamics, the simulation model consisted of major components of electric vehicles such as motor, battery, wheel/tire, brake, and acceleration. Through the development model, the amount of change in battery SOC and the mileage during driving were calculated. For verification, battery SOC data and vehicle speed data were compared and analyzed using CAN communication during the chassis dynamometer test. In addition, the reliability of the simulation model was confirmed through an analysis of the correlation between the result data and the data acquired through CAN communication.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.17-17
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• 2017

In electric agricultural machine the gearhead is needed to convert the high speed low torque rotation motion generated by DC motor to lower speed high torque motion used by the vehicle. The gearhead consist of several spur gears works as reduction gears. Spur gear have straight tooth and are parallel to the axis of the wheel. Spur gears are the most easily visualized gears that transmit motion between two parallel shafts and easy to produce. The modeling and simulation of spur gears in DC motor gearhead is important to predict the actual motion behavior. A pair of spur gear tooth in action is generally subjected to two types of cyclic stress: contact stress and bending stress including bending fatigue. The stress may not attain their maximum values at the same point of contact fatigue. These types of failure can be minimized by analysis of the problem during the design stage and creating proper tooth surface profile with proper manufacturing methods. To improve its life expectation in this study modal and stress analysis of gearhead is simulated using ansys work bench software based on finite element method (FEM). The modal analysis was done to understand gearhead deformation behaviour when vibration occurs. FEM static stress analysis is also simulated on gearhead to simulate the gear teeth bending stress and contact stress behavior. This methodology serves as an approach for gearhead design evaluation, and the study of gear stress behavior in DC motor gearhead which is needed in the small workshop scale industries.

• Design & Manufacturing
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• 제2권1호
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• pp.33-38
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• 2008

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra precision aspherical surface lens increases higher. Precision turning with single-diamond tools has a long history of development for fabrication of optical quality surfaces since the advent of aerostatic rotary spindles and precise linear motion guide ways. To enhance the precision and productivity of ultra precision aspherical surface micro lens, the following specification of ultra precision grinding system is required: the highest rotational speed of the grinder is 100,000rpm and its turning accuracy is $0.1{\mu}m$, positioning accuracy is $0.1{\mu}m$. The development process of the grinding system for the ultra precision aspherical surface micro lens for optoelectronics industry is introduced. In the work reported in this paper, an intelligent grinding system for ultra precision aspherical surface machining was designed by considering the factors affecting the surface roughness and profiles accuracy. An aerostatic form was adopted to build the spindle of the workpiece and the spindle of grinder and ultra precision LM guide way was adopted in this system. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $0.6{\mu}m$ P-V and a surface roughness of $0.006{\mu}m$ Rmax.

• 한국철도학회논문집
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• 제10권5호
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• pp.613-618
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• 2007

철도차량의 곡선주행성능은 유지보수관점에서 매우 중요하다. 곡선주행성능과 관련된 대차의 조향성능은 실차를 이용한 실선로 주행시험이 적전하나 차량 개발단계에서는 이를 검증하기가 용이하지 않다. 따라서 차량의 조향 특성을 효율적으로 시험하기 위한 축소 곡선트랙에 대한 연구를 수행하였다. 대차의 곡선 주행을 모사하기 위한 곡률반경 $200{\sim}250m$의 급곡선과 등가인 1/5 scale 규모의 축소 곡선트랙을 설계, 제작하였다. 1/5 scale 대차를 이용한 주행시험 시험결과 곡선 주행특성이 비교적 잘 반영되고 있음을 확인하였다.