• Tribology and Lubricants
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• 제31권4호
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• pp.141-147
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• 2015

Gas foil thrust bearings (GFTBs) have attractive advantages over rolling element bearings and oil film thrust bearings, such as oil-free operation, high speed stability, and high-temperature operation. However, GFTBs have lower load carrying capacity than the other two types of bearings owing to the inherent low gas viscosity. The load carrying capacity of GFTBs depends mainly on the compliance of the foil structure and the formed hydrodynamic wedge, where the gas pressure field is generated between the top foil and the thrust runner. The load carrying capacity of the GFTBs is very important for the suitable design of oil-free turbomachinery with high performance. The aim of the present study is to identify the characteristics of the load carrying performance of GFTBs. A new test rig for the experimental measurements is designed to provide static loads up to 800 N using a pneumatic cylinder. The maximum operating speed of the driving motor is 30,000 rpm. A series of experimental tests—lift-off test, static load performance test, and maximum load capacity test—estimate the performance of a six-pad GFTB, in terms of the static load, driving torque, and temperature. The maximum load capacity is determined by increasing the static load until the driving torque rises suddenly with a sharp peak. The test results show that the torque and temperature increase linearly with the static load. The estimated maximum load capacity per unit area is approximately 80.5 kPa at a rotor speed of 25,000 rpm. The test results can be used as a design guideline for GFTBs for realizing oil-free turbomachinery.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.59-64
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• 2014

Integrated Starter Generator (ISG) system improves the fuel economy of hybrid electric vehicles by using idle stop and go function, and regenerative braking system. To obtain the high performance and durability of ISG motor under continuously high load condition, the motor needs to properly design the cooling system (cooling fan and cooling structure). In this study, we suggested the enhanced design by modifying the thermal design of the ISG motor and then analyzed the improvement of the cooling performance under high-speed condition and generating mode by CFD simulation. The temperatures at the coil and the magnet of the enhanced model were decreased by about $4^{\circ}C$ and $6^{\circ}C$, respectively, compared to those of the conventional model. Therefore, we verified the cooling performance enhancement of the novel thermal design in the case of core loss increment due to the higher speed condition.

• 한국철도학회논문집
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• 제16권1호
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• pp.14-19
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• 2013

고속철도차량의 실내소음은 승객에서 불쾌감, 피로감 및 스트레스를 유발하는 요인으로 이에 대한 지속적인 연구가 필요하다. 특히, 고속철도 차량이 개활지와 터널 등 다양한 주행환경에서 운행되고 있는 우리나라 현실에서는 이러한 환경에서의 실내소음 변화에 대한 구체적인 연구가 필요하다. 따라서, 본 연구에서는 현재 우리나라에 운영되고 있는 고속철도 차량에 대한 실내 소음의 특성을 분석하는 연구를 수행하였다. KTX와 KTX-산천 차량의 실내에 마이크로폰을 설치하여 주행 시 발생하는 실내소음을 분석하였으며, 축상, 대차 및 차체 가속도 센서를 설치하여 구조기인의 원인이 되는 진동을 검토하였다. 본 연구를 통해서 고속철도 차량의 속도에 따른 실내소음의 특성이 도출되었으며, 주행 환경이 실내소음에 미치는 영향을 개활지와 터널주행 시 발생하는 실내소음의 차이를 통해서 검토하였다. 또한, 차체진동과 실내소음에 대한 전달함수분석을 통해서 차체진동이 실내소음에 미치는 영향을 검토하였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.51-56
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• 2013

With the active development of hybrid electric vehicle (HEV), the application of interior permanent magnet synchronous motor (IPMSM) has been expanded. As wide driving region of IPMSM for electric vehicle (EV) traction motor is required, many studies are conducted to improve characteristics of a motor in both low and high-speed driving regions. A motor in high-speed driving region generates (produces) large stress to the rotor. Thus, the rotor needs to be designed considering the mechanical safety. Therefore, in this paper, we conducted stress analysis and electromagnetic analysis to determine the centerpost's distance which is considered important during the design of IPMSM for EV traction motor in order to secure mechanical safety and satisfy specifications of output requirement.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.132-137
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• 2011

철도차량의 고속화, 경량화와 함께 승객의 안전성을 보다 더 높이기 위한 많은 연구가 진행 되고 있다. 철도차량의 안전성을 높이기 위해서는 주행성능을 안정시키는 것이 무엇보다 중요하며, 드라이빙기어 내부의 윤활유량을 최적화하는 것은 주행성능 확보에 필수적이다. 본 연구에서는 전동차용 Driving Gear Unit의 회전 방향에 따라 저속 Gear 치면을 통해 Splash 되는 드라이빙기어 Casing내의 윤활유 유동 변화를 ANASYS CFD 프로그램과 전산유체해석 기법을 사용하여 구현 하였으며, 해석 내역을 토대로 유사 구동 조건에 대한 무부하 실증 시험을 실시하여 해석의 적합성 및 윤활유량 선정과 드라이빙기어의 안전성에 대해 고찰하였다.

• ETRI Journal
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• 제43권4호
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• pp.603-616
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• 2021

Over the last few years, autonomous vehicles have progressed very rapidly. The odometry technique that estimates displacement from consecutive sensor inputs is an essential technique for autonomous driving. In this article, we propose a fast, robust, and accurate odometry technique. The proposed technique is light detection and ranging (LiDAR)-based direct odometry, which uses a spherical range image (SRI) that projects a three-dimensional point cloud onto a two-dimensional spherical image plane. Direct odometry is developed in a vision-based method, and a fast execution speed can be expected. However, applying LiDAR data is difficult because of the sparsity. To solve this problem, we propose an SRI generation method and mathematical analysis, two key point sampling methods using SRI to increase precision and robustness, and a fast optimization method. The proposed technique was tested with the KITTI dataset and real environments. Evaluation results yielded a translation error of 0.69%, a rotation error of 0.0031°/m in the KITTI training dataset, and an execution time of 17 ms. The results demonstrated high precision comparable with state-of-the-art and remarkably higher speed than conventional techniques.

• 드라이브 ㆍ 컨트롤
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• 제17권4호
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• pp.80-86
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• 2020

Autonomous driving is one of the most important new technologies of our time; it has benefits in terms of safety, the environment, and economic issues. Path following algorithms, such as automated lane keeping systems (ALKSs), are key level 3 or higher functions of autonomous driving. Pure-Pursuit and Stanley controllers are widely used because of their good path tracking performance and simplicity. However, with the Pure-Pursuit controller, corner cutting behavior occurs on curved roads, and the Stanley controller has a risk of divergence depending on the response of the steering system. In this study, we use the advantages of each controller to propose a hybrid control strategy that can be stably applied to complex driving environments. The weight of each controller is determined from the global and local curvature indexes calculated from HD map information and the current driving speed. Our experimental results demonstrate the ability of the hybrid controller, which had a cross-track error of under 0.1 m in a virtual environment that simulates K-City, with complex driving environments such as urban areas, community roads, and high-speed driving roads.

• 한국응급구조학회지
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• 제6권1호
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• pp.199-207
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• 2002

This is a study to evaluate the effects of the safety of ambulance driving and the occurrence of ambulance traffic accidents and to provide basic information for the description of various factors to reduce the ambulance traffic accidents. The major instruments of this study were Korean Self-Analysis Driver Opinionnaire. Questionnaire contains 8 items which measure driver's opinions or attitudees: driving courtesy, emotion, traffic law, speed, vehicle condition, the use of drugs, high-risk behavior, human factor. To take the analysis of data, the total of 187 drivers were investigated ambulance drivers in Gwangju Metropolitan City from 2002. 1. September to 2002. 20. September. The data were analyzed by the path analysis SPSS program. The result are as follows : 1. There was desirable attitude group(58.4%) and undesirable attitude group(41.7%) on safety ambulance driving. 2. It have suggested that rist factors of ambulance traffic accident much affected with emotion and speed control on safety ambulance driving(Y(Accident) = -2.00 + 0.6 X1(Emotion Control) + 0.4 $X_2$(Speed control) + E). 3. Almost 92.1% of respondents have agreed to necessity of emergency medical technics for ambulance drivers.

• 드라이브 ㆍ 컨트롤
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• 제19권4호
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• pp.36-45
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• 2022

The aim of this study was to verify an E-driving system of a 44 kW-class electric tractor using agricultural workload data. Workload data were acquired during field test (plow tillage, rotary tillage, loader operation, field driving, asphalt driving) using a conventional tractor with a load measurement system. These workload data were converted to data of a 44 kW-class tractor based on the load factor of the engine. These data were used to verify the design of the E-driving system of an electric tractor. High-load operations such as plow tillage, rotary tillage, and loader operation could be performed at stage L and stage M. High-speed operation (asphalt driving) could be effectively performed at stage H using a rated rotational speed of the motor. As a result, the E-driving system of the electric tractor was possible to perform all major agricultural operations according to gear stages of range shift. Based on results of this research, we plan to develop an electric tractor equipped with an E-driving system and conduct research on actual vehicle verification in the future.

• 인터넷정보학회논문지
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• 제23권3호
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• pp.47-56
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• 2022

본 논문의 안전운행 보상시스템은 안전운전을 수행한 차량운전자에게 직접적인 보상을 제공하여 안전운전의 동기를 부여하고 적극적 참여를 유도함으로써 사고의 발생을 줄여 생명과 재산의 손실을 줄이는데 목표가 있다. 기존의 디지털 운행기록계의 경우 차량의 운전상태를 기록만 하였으나, 안전운전보상시스템은 사고예방 효과를 높이기 위한 지원책으로서 안전운전을 수행한 경우 금전적 보상을 통해 위험운전을 피하고 안전운전을 하도록 유도하였다. 즉, 과속으로 인한 사고 발생 빈도가 높은 지역에서는 속도 준수, 또는 차 간 거리 유지, 지정차로 운행 등의 안전운행 지시를 수행한 경우 직접적인 보상을 제공함으로써 안전운전 동기를 부여하여 교통사고를 예방하고자 한다. 이러한 안전운행 데이터와 보상내용은 투명하고 안전하게 관리되어야 하므로 보상근거와 보상내용을 폐쇄형 블록체인 하이퍼레저 패브릭을 이용하여 구축하였다. 그러나 블록체인 시스템은 투명성과 안전성이 보장되는 반면에 낮은 데이터 처리속도가 문제가 되므로 이를 개선하고자 블록생성 가속 기능을 구현하였다. 본 연구에서는 순차적으로 블록을 생성하는 속도가 10TPS(Transaction per second) 내외의 낮은 속도를 나타내어, 블록의 생성속도를 높이기 위해 가속 기능을 적용한 결과 1,000TPS 이상의 고성능 네트워크를 구현하였다.