• Journal of Korean Society of Transportation
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• v.30 no.5
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• pp.83-90
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• 2012

Driver ordinarily takes sudden braking when urgent situation is developed or when the vehicle is involved in an unexpected accident. Therefore, the most common trace at a traffic accident scene is skid mark. Currently, in investigating traffic accident, overspeed is determined by the length of skid mark. However, in order to identify accurate cause of accident, estimation of pre-braking speed which takes into account speed reduction during transient time should be considered as a requirement. In a recent study, several ways to estimate pre-braking speed were suggested, but none considered to differentiate the decelerating transient brake section and skidding section. This study analyzed trends of decelerating transient brake section and skidding section by real braking test.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.350-357
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• 2001

본 논문은 고정폐색구간에서 차량운전 특성과 속도패턴이 다양한 다종의 열차들이 동일선로에서 복합되어 고밀도 운행을 위한 방법으로, 신호현시에 대한 제반정보를 차상으로 전송 받아 기관실 신호표시반에 신호를 현시 하는 차상신호방식(Cab Signalling System)중에서, 선행열차의 위치, 선로조건 등 지상의 상태정보를 후속열차가 수신하여 열차 자신의 제동특성 등 차량정보와 비교 분석하여 제동거리를 계산하는 distance to go 방식으로 열차운전속도를 제어하는 ATP (Automatic Train Protection) 시스템을 제안하였다. 폐색구간별 고정된 신호속도단계가 부여되는 ATC(Automatic Train Control) 시스템에서는 운행패턴이 같은 단일차종의 열차만 운행하는 구간에서는 일정속도에 의한 폐색구간 분할로 구간내 distance to go 신호체계가 이루어지지만, 차종과 속도패턴이 서로 상이한 복합열차들의 운행구간에서는 안전거리 확보를 위하여 저속열차의 제동거리를 기준으로 폐색구간 분할 및 속도결정이 이루어지므로 ATP 방식보다 운행효율이 다소 떨어짐을 알 수 있었다. 이를 차량특성과 속도패턴이 다른 3개의 열차를 모델로 하여 열차별 감속도에 의한 제동특성을 ATC와 ATP 신호제어체계에 접목시켜 시뮬레이션을 하였다.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.43-45
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• 2002

본 논문은 SRM의 4상한 운전 조건 중 주스위치의 고정된 스위치 온과 오프각을 가진 PWM 제동제어 방식에 대해 해석하였다. 평균 제동 토오크는 포화되지 않은 자기회로에서 계산되어진다. 또한 여자구간과 커뮤테이션 구간에서의 에너지를 해석하였다. 제안한 PWM 제동제어 방식을 6/4SRM에 적용하여 그 타당성을 검증하였다.

• The Journal of the Convergence on Culture Technology
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• v.10 no.3
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• pp.845-849
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• 2024

Currently, rail surface defects are increasing due to the aging of urban railway rails, but in the detailed guidelines for track performance evaluation established by the country, rail surface damage is inspected with the naked eye of an engineer and with simple measuring tools. It is very important to discover defects in the rail surface through periodic track tours and visual inspection. However, evaluating the severity of defects on the rail surface based on the subjective judgment of the inspector has significant limitations in predicting damage inside the rail. In this study, the characteristics of cracks inside the rail due to rail surface damage were studied. In field measurements, rail surface damage was selected, old rail samples were collected in the acceleration and braking sections, and a scanning electron microscope (SEM) was used to evaluate the rail surface damage was used to analyze the crack characteristics. As a result of the analysis, the crack mechanism caused by the running train and the crack characteristics of the acceleration section where cracks occur at an angle rising toward the rail surface were experimentally proven.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.665-669
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• 2007

This study investigates the temperature change and thermal conductivity for the braking disc of the railway vehicle due to the types of train and service conditions. The temperature change was measured by non-contact Infrared thermometers. Average temperature was measured between $79.32^{\circ}C$ and $104.46^{\circ}C$ due to types of train and service section. In the same service section, the surface temperatures of Saemaul train were higher than Mugungwha train; the reason might have been the average service speed of Saemaul train (83km/h) was higher than Mugungwha train (107km/h), and the weight was similar 39t (Mugungwha) and 39.3t (Saemaul). But the maximum surface temperature was measured on the Mugungwha train; however the difference was not too big with the maximum temperature of Saemaul train. Also, the disc surface temperatures were changed due to the material of lining; metal and non-asbestos, on the same train and the same service section. In addition. the thermal conductivity was tested the thermal conductivities were increased by the increasing of the temperature. The change is too big between $100^{\circ}C$ and $200^{\circ}C$. But each average value is small. and the mechanical property change is very low. As a result, we conclude that this disc is suitable for usage between $100^{\circ}C$ and $300^{\circ}C$.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.426-438
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• 2015

Train speed controlling systems are now changing from wayside systems to onboard signaling systems. Locomotive engineers refer to wayside markers to decide on a braking point when the train speed appears to be lower than the current speed. However, in the onboard signaling systems that have been installed recently, the braking point is not determined by the wayside signal but by an onboard value. In this paper, we studied braking points and methods for deciding on such points by engineers using the onboard systems. An optimized braking point is proposed via simulation of decelerating velocity to control the velocity in the signaling system through a predefined point; Gaussian distributions are used to simulate the actual situation. We estimated and demonstrated how to obtain braking parameters in order to satisfy the interval of permitted error.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.204-212
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• 2010

Currents which are generated at both ends of drive motor by operating brake pedal when subway train is driving, will generate the reviltalization actual effect if they are not used immediately. So there exist rolling stock established Dynamic braking annex for the purpose of stable brake performance in case there are no retrogress train around or no stable wiring voltage.Therefore 55% of entered energy are consumed in subway train. 45% are used in down gradient section or for regeneration energy and among them 25% are used for another train's retrogression through the wiring. So to reduce reviltalization method keeping the existing system, substation's service voltage should be declined about 5%. And then it will ease off excessive wiring voltage rise. And there need energy reduction by flexible service voltage adjustment and study for energy consumption efficiency in the subway.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.93-101
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• 2010

The effects of braking of trains and roughness of rails on the dynamic behavior of bridges are studied. The train-bridge interaction is considered by solving Lagrange's equation of motions. Newmark's direct integration is used to solve the governing equations. Dynamic train loads acting on piers at each time step are evaluated, and the wheel-rail roughness effect is considered by using the PSD curve of the rail. The model of braking forces in bridge section is based on the change of deceleration mentioned in ASTM(American Society for Testing and Materials) E503-82. Only skidding frictions without considering rolling frictions are modeled, and the friction coefficient of 0.25 is assumed. Parametric studies in a simply supported PC Box girder bridge are carried out to verify the present method and to analyze the effects of train speed, wheel-rail roughness, braking forces on dynamic train loads.

• Journal of Drive and Control
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• v.9 no.1
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• pp.1-9
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• 2012

Nowadays, various researches about eco-friendly vehicles such as hybrid electric vehicle, fuel cell vehicle and electric vehicle have been actively carried out. Since most of these green cars have electric motors, the regenerative energy technology can be used to improve the fuel economy and the energy efficiency of vehicles. The regenerative brake is an energy recovery mechanism which slows a vehicle by converting its kinetic energy into electric energy, which can be either used immediately or stored until needed. This technology plays a significant role in achieving the high energy usage. However, there are some technical problems for controlling the regenerative braking and the electro-hydraulic brake during switching at transient region. In this paper, the performance simulator for fuel-cell vehicle is developed and transient response characteristics of the regenerative braking system are analyzed in the various driving situations. And the hardware-in-the-loop simulation of electro-hydraulic brake is performed to validate the transient characteristics of the regenerative braking system for fuel-cell electric vehicle.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1587-1588
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• 2015

일반적으로 국내의 대부분의 전기철도는 단상 교류식이므로 전력계통의 3상 154[kV]을 스코트 변압기를 통해 단상 55[kV]로 변환하여 단상 교류로 공급받는다. 전기철도는 기동 특성 및 제동 특성에 따라 부하의 급증과 급감, 임의의 한 급전 구간 내에 운행 일정 중복으로 다수의 전기철도 차량이 운행될 경우 상호간 전기적 특성이 수시로 변한다. 이와 같은 전기적 특성이 수시로 변하는 전력량은 스코트 변압기에서 전력량을 측정하게 된다. 스코트 변압기 1차측 3상 전력이 2차측 단상 전력으로 변환하는 전기기기이며, 전동차가 제동시 회생전력이 발생되는데 이로인해 스코트변압기의 1차측과 2차측 위상이 다르게 발생되어 계량오차가 발생되는 문제점이 있다. 따라서, 본 논문에서는 계량오차의 문제점을 해결하기 위해, 스코트 변압기 2차측 기준으로 전압과 전류의 위상차를 계산하여 회생전력과 수전전력을 정확하게 계량하여 오차를 판단하고 보정하는 알고리즘을 제시하고자 한다.