• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.107-118
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• 2022

As connected and automated driving(CAD) technology is entering its commercialization stage, service platforms providing CAD-based mobility services have increased these days. However, CAD-baded mobility services with these platforms need more consideration for the demand for mobility services when determining target areas for CAD-based mobility services because current CAB-based mobility design focus on driving performance and driving stability. For a more efficient design of CAD-based mobility services, we analyzed the applicability for the introduction of CAD-based mobility services in terms of driving difficulty of CAD and demand patterns of current non-CAD based-mobility services, e.g., taxi, demand-responsive transit(DRT), and special transportation systems(STS). In addition, for the spatial analysis of the applicability of the CAD-based mobility service, we propose the Index for Autonomous Driving Applicability (IADA) and analyze the characteristics of the spatial distribution of IADA from the network perspective. The analysis results show that the applicability of CAD-based mobility services depends more on the demand patterns than the driving difficulty of CAV. In particular, the results show that the concentration pattern of demand in a specific road link is more important than the size of demand. As a result, STS service shows higher applicability compared to other mobility services, even though the size of demand for this mobility service is relatively small.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.1
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• pp.160-173
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• 2021

Recently, research on the development of autonomous vehicles has increased worldwide. Moreover, a means to identify and analyze the characteristics of traffic accidents of autonomous vehicles is needed. Accordingly, traffic accident data of autonomous vehicles are being collected in California, USA. This research examined the characteristics of traffic accidents of autonomous vehicles. Primarily, traffic accident data for autonomous vehicles were analyzed, and the text data used text-embedding techniques to derive major keywords and four topics. The methodology of this study is expected to be used in the analysis of traffic accidents in autonomous vehicles.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.1
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• pp.47-56
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• 2012

Bicycle has a large amount of kinetic energy available for energy harvesting technology in its speedy and balanced riding movement. Systematic and realistic analysis of its dynamic property is essential to improve the efficiency of energy harvester. However, there has not been enough researches about precise measurement or analysis of bicycle dynamics on real roads. This study aims to investigate the characteristics of vibrational movement of bicycle using MEMS-based accelerometer and to develop a prototype of electromagnetic energy harvester with nonlinear behavior which is proper to the random vibrations accompanied in bicycle riding. The vibrational components have average magnitude of 1 g and turn out to be independent of riding speed. The developed prototype of energy harvester was installed on a front port of a bicycle to use this ambient vibration and generated an average electrical power of 1.5 mW which is enough to support power for most of portable sensors and short range radio-frequency communication. Further study about isolation of vibration from a rider and conversion efficiency is ongoing. The developed energy harvester is expected to be a platform technology for sustainable portable power supply for various smart IT devices and applications.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.2
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• pp.62-73
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• 2022

As the competition among the autonomous vehicle (AV, here after) developers are getting fierce, Korean government has been supporting developers by deregulating safety standards and providing financial subsidies. Recently, some OEMs announced their plans to market Lv3 and Lv4 automated driving systems. However, these market changes raised concern among public road management sectors for monitoring road conditions and alleviating hazardous conditions for AVs and human drivers. In this regards, the authors proposed a methodology for monitoring road infrastructure to identify hazardous factors for AVs and categorizing the hazards based on their level of impact. To evaluate the degrees of the harm on AVs, the authors suggested a methodology for managing road hazard factors based on vehicle performance features including vehicle body, sensors, and algorithms. Furthermore, they proposed a method providing AVs and road management authorities with potential risk information on road by delivering them on the monitoring map with node and link structure.

• Journal of Korean Society of Transportation
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• v.33 no.1
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• pp.40-49
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• 2015

In this study, the effects of inertial driving on a fuel-cut zone were analyzed by measuring the instantaneous variations of fuel consumption and speed. Thirteen sites with 2-8% downhill slopes were selected for the vehicle experiments. The vehicles were driven on the sites in two different driving modes, and the various vehicle states were measured using OBD under driving. For the analysis of the effects of inertial driving, the characteristics of fuel consumption, speed, and rpm were compared between normal and inertial driving. As a result, the fuel consumption was reduced from 24% to 78% according to the downhill grade. The amount of fuel consumption reduction was about 30cc for driving 500m downhill. Fuel cost savings amounting to 35 billion won can be achieved if inertial driving will be done in the case of Munemi-ro3. It is also believed that the reduced fuel consumption and vehicle speed through inertial driving will have considerable environmental and safety benefits.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.108-115
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• 1999

In this study we suggested a digital filter method to enhance car audio sound quality against the sound distortion due to cabin's acoustic characteristics and car driving noises. The digital filters designed were based on the characteristics on car driving noises and cabin acoustic characteristics. Car driving noises were analyzed by two ways; one is an objective method, octave band frequency analysis method. The other is a subjective method; sensory evaluation method, NCB method. On these results, seven sets of modified coefficients of eleven band digital filters were obtained. To find optimum audio sound quality among nine sound samples filtered by designing seven types of digital filters, which were mixed car driving noises at 100km/h, subjective evaluation method was used, paired comparison method; Scheffe' seven point method.

• Journal of the KSME
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• v.33 no.10
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• pp.871-883
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• 1993

차량의 승차감 및 조안 성능을 결정하는 중요한 인자인 현가장치(Supension System) 설계의 최적화를 기하며 실차육성기간을 줄이고 설계 업무의 효율성을 높이기 위하여 각종 차량 특성 인자의 수치화를 통해 여러 가지 해석을 수행하게 된다. 이러한 해석 과정으로는 크게 현가장 치의 기구학적 특성-Kinematic Analysis-과 부시 (Bush)와 스프링 (Spring) 등의 컴플라이언스 (Compliance) 효과 - 쿼지스테틱 어낼러시스 (Quasistatic Analysis)-와 전체차량의 주행 시뮬 레이션 (simulation)을 통한 설계차량의주행안정성 검토-풀 비클 어낼러시스 (Full Vehicle Analysis)- 등이 있다. 이 글에서는 승용차의 현가장치중 대표적인형인 맥퍼슨 스터러트형에 대 하여 1) 기구학적 특성, 2) 부시와 스프링 등의 컴플라이언스 효과, 3) 전체차량의 주행 시뮬레 이션을 통한 차량의 주행 안정성 검토의 순으로 각 단계별 주요 검토 항목과 인자, 그리고 실제 차량에서의 현상에 대하여 소개한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.45-52
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• 2010

A model of the propulsion mechanism, I, II, III was based on a two-dimensional model of the Weis-Fogh mechanism and consisted of one or two wings in a square channel. The sailing and vibration performance characteristics of model ships were tested to compare with each other. we took results as follow. Thrust of propulsion model, I and III was increased by 31% and 43%, the speed of model ship by 20% and 23%, When compared to model II in same condition. The thrust improvement using the elastic spring wing was effective not only on all models but also in the real ship. The maximum amplitude and RMS were largest at the opening angle ${\alpha}=15^{\circ}$ and smallest at ${\alpha}=30^{\circ}$ on the vibration of model ship. The thrust of propulsion model III with opening angle ${\alpha}=30^{\circ}$, phase ${\Delta}T=0^{\circ}$ was large, but the amplitude of vibration was small relatively.

• Journal of Korean Society of Transportation
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• v.22 no.5
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• pp.7-17
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• 2004

지금까지의 링크통행시간에 대한 연구는 개별 차량의 평균을 통한 평균링크통행시간 산정 및 추정의 제한적인 연구가 대부분이었다. 그러나, 링크통행시간은 교통조건, 신호운영조건, 도로조건 등 다양한 영향인자로 인해 통행시간 분포가 구분되는 특성을 나타낸다. 따라서, 링크통행시간 특성을 좀 더 미시적으로 분석할 필요가 있다. 본 연구에서는 GPS를 이용한 실시간 교통자료 수집의 방법에 대해 살펴보았으며, GPS를 이용한 RTK 측량을 이용한 실시간 자료수집을 통하여 링크통행시간에 대한 연구를 수행하였다. 또한, 신호운영에 의한 영향으로 인한 링크통행시간 분포특성을 분석하기 위해 링크통행시간에 대한 현장조사를 추가적으로 실시하였다. 현장조사 결과분석을 통해 통행시간 분포특성 및 원인을 분석하고 프로그램을 이용한 시뮬레이션을 통해 보다 다양한 조건을 부여하여 링크통행시간분포비율에 영향을 주는 변수들에 대한 검토하고 통행시간 분포비율을 추정할 수 있는 모형을 구축하였다. GPS 실험차량을 이용한 주행실험결과를 분석한 결과 순행시간으로만 이루어지는 링크통행시간과 적색시간 동안 대기하였다가 링크구간을 통과하여 순행시간에 신호 대기시간을 더한 링크통행시간으로 통행시간이 구분되는 현상을 확인할 수 있었으며 따라서, 링크통행시간에 대한 분석은 통행시간을 하나의 평균통행시간으로 인식하는 것보다 두 개의 구분된 통행시간을 동시에 고려하는 것이 바람직할 것으로 판단되었다. 링크통행시간 분포특성에 대한 연구결과 또한, 통행시간이 양분되어 분포하는 것으로 분석되었다. 따라서, 링크통행시간의 경우 평균통행시간에 의한 결과보다 신호지체가 발생하지 않는 통행시간과 신호지체가 발생하는 통행시간으로 구분하는 것이 교통상황을 인식하는 것이 바람직할 것으로 나타났다.

• Journal of Korean Society of Transportation
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• v.36 no.1
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• pp.38-50
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• 2018

Emerging automated driving environments will lead to a mixed traffic flow depending on the interaction between automated vehicles (AVs) and manually driven vehicles (MVs) because the market penetration rate (MPR) of AVs will gradually increase over time. Understanding the characteristics of mixed traffic conditions, and developing a method to control both AV and MV maneuverings smoothly is a backbone of the traffic management in the era of automated driving. To facilitate smooth vehicle interactions, the maneuvering of AVs should be properly determined by various traffic and road conditions, which motivates this study. This study investigated whether the aggressiveness of AV maneuvering, defined as automated driving aggressiveness (ADA), affect the performance of mixed traffic flow. VISSIM microscopic simulation experiments were conducted to derive proper ADAs for satisfying both the traffic safety and the operational efficiency. Traffic conflict rates and average travel speeds were used as indicators for the performance of safety and operations. While conducting simulations, level of service(LOS) and market penetration rate(MPR) of AVs were also taken into considerations. Results implies that an effective guideline to manage the ADA under various traffic and road conditions needs to be developed from the perspective of traffic operations to optimize traffic performances.