• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.135-144
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• 2016

It is essential to lighten the weight of switch girders in order to reduce their costs of manufacturing and make it easier to use them in construction. Lightening the weight of switch is also important to the Maglev 3-way switches system, however, the design variables should be considered very carefully if lightening is to be applied to the system, because these variables are vitally related to the levitation stability. Because Urban Maglev trains have a structure in which train bogie wraps around the guiderail, the adjustment of a girder's height is a possible way to reduce the weight. The safety of the application of this concept is ensured by repeated experiments in a test bed, however, due to a lack of space and budget limits, the design parametric study for the system model can substitute for actual application. The purpose of this paper is to study the design parameters that are concerned with levitation stability while a Maglev train is running on the Maglev 3-way system depending on the weight of the switch girders. In this study, switch girder weight is reduced by adjustment of girder height and girders are and modeled as a flexible body. The effect of the adjustment of girder height on the levitation stability can be analyzed by comparing the velocity of the train when it passes the switch girders, with the lateral gap, and the levitation gap which are obtained from the co-simulation of the Maglev train's dynamics model and flexible switching system. The results of this research will be used to design a Maglev switch.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.576-582
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• 2017

The switching system in a maglev train is an indispensable element for distributing train routes, and it should be designed to ensure safe operation. Unlike conventional wheels on rails, the switching track in EMS-type maglev is supported by a group of 3 to 4 steel girders. When the vehicle changes its route, the segmented track allows the girders to change from a straight position to a curved one with a small radius of curvature. Hence, the structural characteristics of the segmented switching system may affect the levitation stability of the maglev vehicle. This study experimentally evaluates the dynamic interaction between maglev vehicles and a segmented switching system. The results may be helpful for improving the switching system. The measured levitation and lateral air gaps were evaluated at a vehicle speed of 25 km/h, and the ride quality of the Maglev vehicle was determined to be "comfortable" according to the UIC 513 standard.

• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.311-319
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• 2017

The primary suspension system of a railway vehicle restrains the wheelset and the bogie, which greatly affects the dynamic characteristics of the vehicle depending on the stiffness in each direction. In order to improve the dynamic characteristics, different stiffness in each direction is required. However, designing different stiffness in each direction is difficult in the case of a general suspension device. To address this, in this paper, an optimization technique is applied to design different stiffness in each direction by using a conical rubber spring. The optimization is performed by using target and analysis RMS values. Lastly, the final model is proposed by complementing the shape of the weak part of the model. An actual model is developed and the reliability of the optimization model is proved on the basis of a deviation average of about 7.7% compared to the target stiffness through a static load test. In addition, the stiffness value is applied to a multibody dynamics model to analyze the stability and curve performance. The critical speed of the improved model was 190km/h, which was faster than the maximum speed of 110km/h. In addition, the steering performance is improved by 34% compared with the conventional model.

• Journal of agriculture & life science
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• v.53 no.4
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• pp.113-124
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• 2019

In this study, the operational characteristics of a cam-type vegetable transplanter which usually used in domestic was analyzed and operating mechanism of a transplanting device was analyzed. The main components and power path of the transplanter were analyzed. The maximum and minimum control cycles according to the moving speed and the plant spacing were analyzed. 3D modeling and simulation were performed to derive the trajectory of the bottom end of the transplanting hopper and the plant spacing at the each operating condition. The simulation results were verified by the field tests. As main findings of this study, the transplanting device has one degree of freedom (DOF) which consist of 13 links, 17 rotating joints and 1 half joint, and each part has composite structure with cam and links. By continuous and repetitive motion of the structures of transplanting device, the transplanting hopper plants the seedling in the ground with a vertical direction, and the seedling was planted stably. The power is transmitted to the driving part and transplanting device from the engine, and the maximum and minimum plant spacing of the transplanting device were about 900 mm and 350 mm, respectively.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.129-141
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• 2006

The vertical soil pressure developed in the granular layer of asphalt pavement system is influenced by various factors, including the wheel load magnitude, the loading speed, and asphalt pavement temperature. This research observed the distribution of vertical soil pressure in pavement supporting layer by investigating measured data from soil pressure gage in the KHC Test Road. The existing specification of subbase and subgrade compaction was also evaluated with measured vertical pressure. The finite element analysis was conducted to verify the accuracy of results with measured data because it can maximize research capacity without significant field test. The test data was collected from A5, A7, A14, and A15 test sections at August, September, and November 2004 and August 2005. Those test sections and test data were selected because they had best quality. The size of influence area was evaluated and the vertical pressure variation was investigated with respect to load level, load speed, and pavement temperature. The lower speed, higher load level, and higher pavement temperature increased the vertical pressure and reduced the area of influence. The finite element result showed the similar trend of vertical pressure variation in comparison with measured data. The specification of compaction quality for subbase and subgrade is higher than the level of vertical pressure measured with truck load so that it should be lurker investigated.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.3
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• pp.15-28
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• 2008

According to the accident statistics published by the National Police Agency in 2006, it can be recognized that drivers' characteristics and driving behaviors are the most causational factors on the traffic accidents. At present, although many recording tools such as digital speedometer or black box are distributed in the market to meet social requests of decreasing traffic accidents and increasing safe driving behaviors, it is also true that it still lacks in obvious categories for dangerous driving types and then, the efficiency of the categories to be studied has been low. In this study, dangerous driving types are redefined. They are grouped into 7 classifications in the first level, and the seven classifications are regrouped into 16 in more detail. To verify the redefined dangerous driving types, a Data-logger is developed to receive and analyze the data that occur from the driving behaviors of the test vehicle. The developed Data-logger can be used to construct a real time warning system and safe driving management system with dangerous driving patterns based on acceleration, deceleration, Yaw rate, image data, etc.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.98-104
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• 2012

Current [Guideline for Installation and Management of Sidewalks and Safety Facilities on Roads] suggests that the types of curbs should be Barrier curb ($85^{\circ}$). Although Barrier curbs ($90^{\circ}$) were not specified in the guideline. The curbs installed on the roads currently are Barrier curbs ($90^{\circ}$) which are not specified in the installation standard. Therefore, it is critical to prepare for the installation standard of curbs by researching types of curbs and driving safety. This research have assessed the driving safety throughout Full Scale Crash Test according to type of curbs (Barrier curbs ($85^{\circ}$) and Barrier curbs ($90^{\circ}$)). Barrier curbs ($90^{\circ}$) showed higher figure in Theoretical head Impact Velocity, Post-impact Head Deceleration, Vehicle Damage when Crash, Passenger's Wounds Severity, and every other items than Barrier curbs ($85^{\circ}$). Barrier curbs ($85^{\circ}$) were found to have better Occupant Safety Index. Analysis of Behavior Using Full-Scale Crash Test showed difference depending on the Impact Condition between Barrier curbs ($85^{\circ}$) and Barrier curbs ($90^{\circ}$). Generally, Barrier curbs ($85^{\circ}$) were superior than Barrier curbs ($90^{\circ}$) in terms of protecting the passengers and vehicle damages. When an impact angle increases, Acceleration of Vehicle, Variations of Speed, and Contact Relationship between Wheels and Curbs, two types of curb showed similarity. However, if an impact of an angle decreases, Barrier Curbs ($85^{\circ}$) showed excellence in Driving Safety such as Acceleration of Vehicle, Variations of Speed, and Contact Relationship between Wheels and Curbs.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.812-817
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• 2011

Rolling stocks are often subjected to the effects of natural cross wind or train wind pressure due to the crossing train. These wind pressure cause the falling-off in running stability and turnover problem. It is sometimes reported that trains are blown over by a gust of wind in overseas. So, many countries enact regulations to secure the safety for wind speed. In this study, we analyzed the difference between the regulation for turnover safety of train which was enacted by Ministry of Land. Transport and Maritime Affairs and that based on the multi-body model. In case of multi-body model, it is assumed that the degrees of freedom for carbody and bogie are assigned an independent values respectively. The results show that the latter approach based on multi-body model can access the safety of turnover and replace the computational method which is accessing with lateral force, derailment coefficient and decrement of wheel load.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.2
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• pp.133-139
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• 2016

An electric wheelchair is a assistive device to maneuver on the ground. Tip-over of an electric wheelchair is increasing every year. Dynamic stability metric test item in KS P 7176 has not ensured safety of electric wheelchair on the slope. This study presents design the foldable electric wheelchair that can load in the car and analysis of tip-over measurement which is easily computed for electric wheelchair. Wheelchair frame is designed with a four-bar link mechanism for a foldable structure, and seat module, battery and power driving module can be separated. This analysis is performed during a maneuver on the ground by force-moment stability metric. Several elements, center of gravity position, rotational radius and acceleration, were evaluated how to affect stability metric. This stability metric can reduce tip-over of wheelchair and provide a clue to make of dynamic stability test item.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3197-3202
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• 2013

When car builder designs the large carbody structure of railway vehicles, it is necessary to optimize the damping characteristics through the analysis of structure borne noise such as sound pressure level(SPL). This paper is a study on the structure borne noise analysis by characterizing the damping of double skin aluminum extruded panels for rolling stock carbody. The normalized SPL was calculated based on the simple source theory using measured mechanical mobility parameters from vibration tests(i.e. point, transfer and modal mobility). The reduced SPL was predicted by using finite element method by applying loss factor of damping material into laminated shell elements. It was found out that the damping material coated on the panels like underframe, which part is seriously affected by vibration during train run, took effect to reduce noise level.