• 한국자동차공학회논문집
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• 제21권1호
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• pp.92-98
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• 2013

There are lots of studies about hybrid electric vehicles (HEVs) because of the global warming and energy problems. Series and parallel HEVs are the common types of many developing hybrid vehicle types. Series HEV uses engine only as the generator for the battery but parallel HEV utilizes engine for driving and generating of the vehicle. In this paper, backward simulations based on dynamic programming were conducted for the fuel economy analysis of two different types of hybrid transit buses depending on driving cycles. It is shown that there is a relation between the type of HEV and the characteristics of driving cycles. Regarding the aggressiveness, the series hybrid bus is more efficient than the parallel system on highly aggressive driving cycle. On the other hand, the parallel hybrid bus is more efficient than the series system on low aggressive driving cycle. Based on this results of the paper, it is expected to choose more efficient type of the hybrid buses according to the driving cycle.

• 한국기계가공학회지
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• 제12권2호
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• pp.27-33
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• 2013

In this study we analyzed the on-road driving performance of two parallel-type diesel-hybrid buses which have been driven in Daegu metropolitan area. A real-time on-board data logger was facilitated to measure the vehicle information such as vehicle speed, idle stop, state of charge of battery, and engine operating conditions. These diesel-hybrid buses ran as a commuter at Daegu Exco area and Dalsung industrial complex. The driving pattern in Exco area comprised more frequent idle stop and relatively lower speed than at Dalsung area, where comprised no idle stop. Due to those different driving patterns, the fuel economy at Dalsung showed $3.7\;km/{\ell}$, which is about 8% higher than that of Exco. The main causes of this come from the higher portion of regenerative braking and higher speed which moves to the operating points of diesel engine with a lower fuel consumption.

• 전기전자학회논문지
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• 제26권3호
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• pp.437-444
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• 2022

본 논문에서는 차량용 반도체에서 CRC 검사를 통해 전송 오류를 검출할 수 있는 SPI 버스 및 I2C 버스를 제안한다. 차량용 반도체에서는 전송에 오류가 발생하여 잘못된 값이 전달되는 경우 치명적인 결과가 발생한다. LIN 버스, CAN 버스와는 다르게 SPI와 I2C 등 구조가 간단한 직렬 인터페이스에서는 전송 오류를 검출하는 방법이 없기 때문에 직렬 인터페이스에 적용할 전송 오류 검출방법을 제시할 필요가 있다. 본 논문에서는 SPI 및 I2C의 통신 프로토콜에 CRC 검사를 사용하여 전송 오류를 검출하는 방법을 제시하고 이를 FPGA로 설계하여 효과적으로 오류를 검출할 수 있음을 검증하였다.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.265-272
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• 2016

The objective of vehicle aerodynamic design is on the fuel economy, reduction of the harmful emission, minimizing the vibration and noise and the driving stability of the vehicle. Especially for a sedan, the driving stability of the vehicle is the main concern of the aerodynamic design of the vehicle indeed. In this theoretical study, an evaluation algorithm of aerodynamic driving stability of a vehicle was made to estimate the dynamic stability of a vehicle at the given driving condition on a road. For the stability evaluation of a driving vehicle, CFD simulation was conducted to have the rolling, pitching and yawing moments of a model vehicle and compared the values of the moments to the resistance moments. From the case study, it is found that a model sedan running at 100 km/h in speed on a straight level road is stable under the side wind with 45 m/s in speed. But the different results may be obtained on the buses and trucks because those vehicles have the wide side area. From the case study of the model vehicle moving on 100 km/h speed with 15 m/s side wind is evaluated using the numerical algorithm drawn from the study, the value of yawing moment is $608.6N{\cdot}m$, rolling moment $-641N{\cdot}m$ and pitching moment $3.9N{\cdot}m$. These values are smaller than each value of rotational resistance moment the model vehicle has, and therefore, the model vehicle's driving stability is guaranteed when driving 100 km/h with 15 m/s side wind.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.90-98
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• 2005

HMT is a type of continuously variable transmission which has split power flow path characteristics with gear train and hydro static unit. The benefit of improved fuel economy and high power capacity enables it to be a promising application fur large vehicles. This paper presents the analysis results including velocity, static torque, transmission efficiency and dynamic model of the HMT that is developed for city buses. The speeds or gear shafts, the static clutch torque and split power ratio for each mode are detailed here. From the analysis of HMT transmission efficiency considering the power loss in meshed gear and hydraulic unit, we can conclude that minimization of hydraulic power is necessary for improved fuel economy design. Also, the dynamic simulation result for mode shift characteristics shows that little shift shock is observed because of the synchronized rotation speed in clutch.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권5호
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• pp.451-458
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• 2013

This paper describes a design of LIN MCU using efficient memory accessing architecture which provides concurrent data and address fetch for faster communication. By using slew rate control it can reduce EMI emission while satisfying required communication specifications. To verify the efficiency of the LIN MCU, we developed a SoC and tested for several data packets. Measurements show that this LIN MCU improves network efficiency up to 17.19 % and response time up to 31.26 % for nominal cases. EMI radiation also can be reduced up to 10 dB.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.144-151
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• 2008

The bi-modal vehicle is composed of two car-bodies and three axles. Each axle of the vehicle has an independent suspension and all wheels are steerable. Since the bi-modal vehicle has longer wheelbase than most urban buses, the All-Wheel-Steering(AWS) system is adapted for to ensure safe driving and proper turning radius on a curved road. This paper proposes an AWS control algorithm for stable driving of bi-modal vehicle. Steering angles and directions of each axle of bi-modal vehicle changed according to the driving environment and steering modes. In the case that front and rear axles should be steered in opposite directions is a negative mode, and the other case that the axles should be steered in the same direction is a positive mode. For example, in the positive mode, front and real axles are steered in the same direction, while in the negative mode, they are steered in the opposite direction. A multibody model of the vehicle is used to verify the performance of the steering algorithm and simulation results of 2WS are compared with those of AWS under the same condition.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.146-153
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• 2013

CNG buses has contributed to improve air quality in cities. But it is difficult to meet the next emission regulations such as EURO-VI without the help of additional post-processing device. Hydorgen has higher flame speed and lower combustion temperature that make it thermal efficiency increase with leaner operation. Using hydrogen natural gas blend (HCNG) fuel is promising technology which can reduce $NO_x$ and $CO_2$ emissions for a natural gas vehicle. However, fuel flow rate of HCNG should be increased since hydrogen's energy density per volume is much smaller than natural gas. In the present study, the characteristics of fuel supply system and its applicability were evaluated in a heavy duty natural gas engine. The results showed that the potential of fuel pressure regulator and fuel metering valve had enough capacity with HCNG. Employed mixer did not affect the distribution characteristics of mixture.

• 전력전자학회논문지
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• 제24권6호
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• pp.438-444
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• 2019

In this paper, bidirectional LLC resonant DC/DC converters with the primary auxiliary windings in transformers of resonant circuits are proposed. Although the resonant capacitors are used on both the primary and secondary sides, regardless of the direction of power flow, the main feature of the proposed converters exhibits high gain characteristics without any mutual coupling between the resonant capacitors. For one of the proposed converters, an investigation of the operating characteristics in each mode has been carried out. A prototype of a 3.3 kW bidirectional LLC resonant converter for interfacing 750 V DC buses has been built and tested to verify the validity and applicability of the proposed converter.

• 한국산학기술학회논문지
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• 제17권9호
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• pp.133-140
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• 2016

국토교통부에서는 교통약자의 이동 편의 증진을 위하여 승하차에 편리한 저상버스를 도입하였다. 표준모델로 고시된 저상버스는 11 m 급, 압축천연가스(CNG, Compressed Natural Gas)를 사용하는 차량으로 개발되었다. 11 m 급 저상버스는 길이 좁은 농어촌 및 산간지역 도로여건에서의 운행과, CNG 연료의 특성상 충전시설의 한계로 인하여 연료보급의 단점을 가지고 있다. 본 연구에서는 국토교통부에서 교통약자의 이동편의 증진을 위해 진행하는 중형저상버스 표준모델 기술개발 과제의 일환으로 (주)타타대우상용차에서 제작한 LF-40을 대상으로 공차(CVW, Curb Vehicle Weight), 반적차(HVW, Half Vehicle Weight), 적차(GVW, Gross Vehicle Weight) 3가지 중량조건으로 실도로 타행주행을 통하여 주행저항 값을 취득하였고, WHVC, NIER-06, 복합 에너지 소비효율 측정 대상차량 외 차량의 에너지 소비 효율을 측정하기 위한 시험 방법인 정속주행 (60 km/h)모드를 사용하였다. 시험 결과 공차상태의 연비가 가장 좋았으며, 대표적으로 WHVC 모드에서는 공차대비 반적차는 3.5 %, 공차대비 적차는 12 % 연비소모율의 차이를 보였다. 60 km/h 정속 주행모드에서는 다른 시험모드와 다르게 공차보다 반적차의 연비가 높은 것으로 측정되었다. 추후 배출가스 데이터의 분석이 필요할 것으로 판단된다.