• International Journal of Automotive Technology
• /
• 제1권1호
• /
• pp.17-25
• /
• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• 한국자동차공학회논문집
• /
• 제19권6호
• /
• pp.53-60
• /
• 2011

The effect of exhaust heat recovery system can be evaluated by two well known method. First method is to measure the time duration from engine start under cold coolant temperature till coolant get warmed. By this methodology coolant warming duration can be index of warm-up effect. Second method is to analyze heat balance of the engine during warm-up phase under steady engine operation so that wasted energy by losses such as cooling and exhaust can be index of warm-up effect. This study focused on evaluation of warming-up effect by both methodology above mentioned using 2L SI engine under from idle to 2000rpm steady condition. Results, idle operation showed low heat recovery efficiency but under higher engine speed condition, remarkable heat recovery efficiency improvement was observed. In 2000rpm steady condition, warm-up duration of engine is decreased by exhaust heat recovery system.

• 한국자동차공학회논문집
• /
• 제3권6호
• /
• pp.224-237
• /
• 1995

An ECU(Electronic Control Unit) with 16 bit microcomputer has been developed. This system includes hardware and software for more precise control on fuel injection, ignition timing, and idle speed. This control system employs an air flow sensor of the hot wire type, a direct ignition system, an idle speed control system using a solenoid valve, and a crank angle sensor. Especially, the crank angle sensor provides two separate signals: One is the position signal(POS) which indicates 180 degree pulses per revolution, and the other is the reference signla(REF) that represents each cylinder individually. The conventional engine control system requires at least two engine revolutions in order to identify the cylinder number. However, the developed engine control system can recognize the cylinder number within a quarter of an engine revolution. Therfore, the developed engine control system has been able to control fuel injection and ignition timing more quickly and accurately, Furthermore, the number of misfire reduces during the cold start.

• 한국자동차공학회논문집
• /
• 제19권4호
• /
• pp.114-120
• /
• 2011

Fuel reforming technology for the fuel cell vehicles has been frequently applied to internal combustion engine for the reduction of engine out emissions. Since syngas which is reformed from fossil fuel has hydrogen as a major component, it has abilities to enhance the combustion characteristics with wide flammability and high speed flame propagation. In this paper, syngas was feed to a 2.0 liter SI engine with MPI to improve exhaust emissions under cold start and early state of idle condition. Syngas fraction is varied to 0%, 10%, 25%, with various ignition timings. Exhaust emission characteristics and the exhaust system temperature were measured to investigate the effects of syngas addition on cold start. Result showed that HC emission could be dramatically reduced due to the fact that syngas has $H_2$ and no HC as components. The amount of $NO_x$ emission was decreased with the increase of syngas fraction. Because the dilution effect of $N_2$ and the retard of ignition timing reduces the peak combustion temperature inside the cylinder. Exhaust gas temperature was lower than that of gasoline feeding condition. Retarded ignition timing, however, resulted in increased exhaust gas temperature approximated to gasoline condition. It is supposed that the usage of syngas in an SI engine is an effective solution to meet the future strict emission regulations.

• 한국자동차공학회논문집
• /
• 제23권4호
• /
• pp.410-419
• /
• 2015

In this study, the roadability, fuel economy and emission characteristics were evaluated for a natural gas converted vehicle. The results are as follows; Not only the shortage of power was observed in stall test, but also large deterioration of acceleration performance was exposed in roadability. Compared to the original LPG system, the acceleration is 76% in start acceleration and 45 ~ 65% in overtaking acceleration, especially the decline became larger when air conditioner is at work. Furthermore, because the mapping data, which controls the injection depending on driving condition, do not match up with injection system, the failure of air-fuel ratio feedback control occurs resulting from the large gap between the required and the really supplied amount of fuel. This failure cause the exhaust gas to emit without catalytic conversion and the fuel economy based on the fuel heat value to get worse 22% in the mode test and 16% in road test respectively. In addition, the existing injection system does not secure enough fuel at the starting so that it may lead to the fail of clod start, the deterioration of hot start and inharmonic of engine at the idle after start.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2011년도 전력전자학술대회
• /
• pp.236-237
• /
• 2011

고유가 시대의 도래와 화석연료의 소비를 줄일 수 있는 환경 친화적 자동차인 하이브리드 자동차의 도입이 일본, 미국 등을 중심으로 꾸준히 증가하고 있다. 이 중 마일드 하이브리드 시스템은 Idle Stop-Start, Launch Assist 및 회생 제동 등의 기능을 적용하여 연비개선의 효과를 갖고 있다. 본 논문에서는 기존 화석 연료를 사용하는 자동차에도 적용이 가능하며 2차 전지에 비해 수명이 긴 슈퍼 커패시터를 사용하여 MHEV용 5kW급 저압 인버터 시스템을 개발하였다.

• Industrial Engineering and Management Systems
• /
• 제6권2호
• /
• pp.106-118
• /
• 2007

This paper present a new optimization model to generate aggregate production planning by considering electric cost. The new Time Of Switching (TOS) electric type is introduced by switching over Time Of Day (TOD) and Time Of Use (TOU) electric types to minimize the electric cost. The fuzzy demand and Dynamic inventory tracking with multiple plant capacity are modeled to cover the uncertain demand of customer. The constraint for minimum hour limitation of plant running per one start up event is introduced to minimize plants idle time. Furthermore; the Optimal Weight Moving Average Factor for customer demand forecasting is introduced by monthly factors to reduce forecasting error. Application is illustrated for multiple cement mill plants. The mathematical model was formulated in spreadsheet format. Then the spreadsheet-solver technique was used as a tool to solve the model. A simulation running on part of the system in a test for six months shows the optimal solution could save 60% of the actual cost.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제8권11호
• /
• pp.3638-3654
• /
• 2014

Cognitive Radio (CR) users need to sense the environment or channel at regular time interval for sharing the spectrum band of the primary users (PUs). Once find the spectrum idle, CR users start their transmission through it. Even while transmitting, they need to continue the sensing process so that they can leave the spectrum immediately whenever find a PU wanting to use the band. Therefore, detecting PUs is one of the main functions of cognitive radio before transmission and higher the detection probability ensures better protection to the primary users. However, it is not possible to attain a high detection probability (or a low miss detection probability) and low false alarm probability simultaneously as there is a tradeoff between false alarm probability ($P_{fa}$) and the probability of detection ($P_d$). In this paper, the author has provided a comprehensive study on different sensing techniques and discussed their advantages and disadvantages. Moreover, it is expected that, with this article, readers can have a through understanding of sensing techniques in CR and the current research trends in this area.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.401-402
• /
• 2014

State of Charge (SOC) and State of Health (SOH) are the key issues for the application of Absorbent Glass Mat (AGM) type battery in Idle Start Stop (ISS) system which is popularly integrated in Electric Vehicles (EVs). However, battery parameters strongly depend on SOC, current rate and temperature and significantly change over the battery life cycles. In this research, a novel method for SOC, SOH estimation which combines the Auto Regressive with external input (ARX) method using for online parameters prediction and Dual Extended Kalman Filter (DEKF) algorithm considering hysteresis is proposed. The validity of the proposed algorithm is verified by the simulation and experiments.

• 한국ITS학회 논문지
• /
• 제8권1호
• /
• pp.102-109
• /
• 2009

본 논문에서는 타임 슬롯의 사용되지 않는 구간에서 효과적으로 CSMA를 수행하여 Hybrid TDMA/CSMA 프로토콜의 성능을 향상시키는 방법을 제안한다. Hybrid TDMA/CSMA 프로토콜은 디바이스들이 효율적으로 매체를 공유하기 위한 방법으로 TDMA 타임 슬롯의 사용되지 않는 구간을 CSMA 접속 방법을 이용하여 채널의 효율성을 높이고 성능을 개선한다. 그러나 CSMA 구간동안 여러 디바이스들이 경쟁을 벌이기 때문에 지연과 잦은 충돌이 발생하여 네트워크 성능이 낮아진다. 본 논문에서는 이러한 문제점을 개선하기 위하여 타임 슬롯에 따라 여유 구간에서 CSMA를 수행하는 디바이스를 제한하는 방법을 제안한다. 제안된 알고리즘은 CSMA 구간에서 경쟁을 벌이는 디바이스의 수를 줄여 경쟁으로 인한 전송 지연과 충돌 가능성을 감소시킨다. 이러한 지연과 충돌 가능성의 감소는 네트워크의 성능을 향상시킨다. 시뮬레이션을 통하여 본 논문에서 제안한 제한적 CSMA 방법과 기존의 Hybrid TDMA/CSMA 프로토콜의 성능을 비교하여 성능 향상을 검증한다.