• Journal of Mechanical Science and Technology
• /
• 제17권11호
• /
• pp.1725-1731
• /
• 2003

A high level CVT ratio control algorithm is proposed to improve the engine performance by considering the powertrain response lag. In this algorithm, the desired CVT speed ratio is modified from the vehicle velocity, which is estimated after the time delay due to the powertrain response lag. In addition, the acceleration map is constructed to estimate the vehicle acceleration from the throttle pedal position and the CVT ratio. Using the CVT ratio control algorithm and the acceleration map, vehicle performance simulations are performed to evaluate the engine performance and fuel economy. It is found that the fuel economy can be improved about 3.6% for FUDS by the ratio control algorithm for the target vehicle. In selecting the appropriate time delay, compromise between the fuel economy and the acceleration performance is required.

• 한국자동차공학회논문집
• /
• 제9권4호
• /
• pp.131-138
• /
• 2001

In this paper, performance of a dry CVT vehicle with torque cam is investigated. Based on belt transmission mechanism and torque cam actuator characteristics, an algorithm which is able to calculate the speed ratio from given thrust and load torque is suggested and a 3-D map is constructed for the speed ratio-thrust-torque. Using the 3-D map, a steady state characteristic of torque cam and a transient response of a dry CVT vehicle are investigated by simulation. It is found that initial spring compression plays a key role in determining the sliding criteria and the speed ratio velocity.

• 대한기계학회논문집
• /
• 제17권9호
• /
• pp.2181-2190
• /
• 1993

An electro-hydraulic controlled rig type CVT(Continuously Variable Transmission) system was developed and its performance tests were carried out for the optimal operation. A CVT map was suggested based on the speed ration-axial force-torque relationship which was derived from the metal belt CVT mechanics. Also, a real time control and operation software was developed for the electro-hydraulic CVT system. By using the software and the CVT map, the control system was designed for the CVT speed ratio control with various drive modes. The electro-hydraulic CVT system developed in this study showed that the optimal operation algorithm could be obtained for the best fuel economy or the maximum power mode.

• 한국주조공학회지
• /
• 제8권4호
• /
• pp.429-436
• /
• 1988

The influences of some casting conditions on bonding ratio and state at bonding zone of stainless steel-cast iron dual tube produced by centrifugal casting process were investigated to estimate fabrication technics. 1) Bonding ratio is increasing such as increasing of inner surface temperature of outer metal(stainless steel STS 304), if pouring temperature of inner metal (cast iron) is constant. 2) The more pouring temperature of inner metal (cast iron) increase, the more bonding ratio increase when inner surface temperature of outer metal (cast iron) is constant. 3) As the mold rotary speed is increase, the hatching area of bonding map (perfect bonding area) goes down to the low pouring temperature of inner metal. 4) In order to predict bonding state of two different metal, we are able to make and use the bonding map about casting conditions such as inner surface temperature of outer metal, pouring temperature of inner metal and mold rotary speed.

• 한국자동차공학회논문집
• /
• 제8권3호
• /
• pp.85-97
• /
• 2000

In this paper, static and dynamic shift control stategies of CVT speed ratio are suggested. For the static shift control, in order to operate engine on the optimal operating region, a fuzzy control logic is used. In the fuzzy logic, S- factor that is defined as a degree of sportiness is introduced. Simulation results show that the static shift control strategy based on the fuzzy logic selects the optimal operating point automatically between the economy and the sporty mode corresponding to the driver's desire and the driving condition. For the dynamic shift control strategy, a shift speed map is suggested which determines the shift sped as fast or slow based on Δi, the difference between the desired speed ratio id and the actual speed ratio i, and throttle opening. It is seen from the simulation results that the CVT shift speed is determined by the dynamic shift control strategy to provide appropriate performance and comfort for the driver's demand and driving condition. Additionally, experiments are performed to investigate the dynamic performance of the shift speed for the lift foot up. From the experimental results, it is found that improved shift feeling can be obtained by the dynamic shift control strategy when lift foot up occurs.

• 한국자동차공학회논문집
• /
• 제5권6호
• /
• pp.111-119
• /
• 1997

In this paper, engine-CVT consolidated control performance were investigated experimentally. Engine-CVT consolidated control was composed of engine throttle control based on power difference and CVT ratio control based on CVT ratio map. Experimental results showed that engine optimal operation was obtained while satisfying the driver's desire, i. e., following the given drive mode by engine-CVT consolidated control. Also, it was found that engine performance is subjected to inertia of the powertrain where the magnitude of acceleration changes abruptyly. Comparing with the results of CVT only control, the results of engine-CVT consolidated control showed better performance. Therefore, in order to meet the driver's desire as well as keeping the engine optimal operation, the engine-CVT consolidated control could be suggested as an integral solution.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
• /
• pp.33-40
• /
• 1999

Upgrade development of a high pressure ratio centrifugal compressor in marine engine turbochargers is presented. A new matched operating point at increased speed of rotation was determined through system cycle analysis using the exisitng test data of turbine performance. Under some severe restrictions for geometric parameters, the state-of-the-art methods of both aerodynamic design and CFD analysis were applied, in which only an impeller, a vaned diffuser and some part of casing wall were modified. Prototype hardware was fabricated and assembled for system performance tests. Excellent performance in pressure ratio and efficiency was obtained over whole speed region. Reduced surge and choke margin was, however, observed at design speed of rotation.

• 한국지구과학회지
• /
• 제34권7호
• /
• pp.633-644
• /
• 2013

풍력 발전단지의 효율성 평가를 위하여 풍력-기상자원지도로부터 이론적 잠재량을 계산하고 행원 발전단지 발전량과 비교하였다. 풍력-기상자원지도는 기상청 국립기상연구소에서 개발된 1 km 해상도 자료를 이용하였다. 풍력-기상자원지도와 AWS(구좌) 풍속의 비교 검증 결과는 풍속이 과대 모의되었으며, 행원 발전단지 풍속의 일 변동성은 해륙풍의 영향으로 오후에 최대가 되는 일 변동 특성을 보였다. 풍력-기상자원지도로부터 산출된 발전량과 행원 발전단지 발전량의 비율은 24.8%이나, 발전량 빈도수 분포 형태는 유사하였다. 발전량 차이의 원인은 터빈의 기계적 오류, 풍력-기상자원지도 풍속의 과대 모의에 기인한 것으로 생각된다. 본 연구는 향후의 발전단지 효율성 증가를 위한 터빈의 재배치에 기여 할 것이다.

• 지적과 국토정보
• /
• 제51권1호
• /
• pp.97-110
• /
• 2021

본 연구는 도로의 실시간 교통정보를 이용하여 법정허용속도로 이동하는 시간과 실제속도로 이동하는 시간의 비율인 지연계수를 산정하였다. 연구의 대상지는 우리나라의 수도인 서울을 대상으로 하였다. 도로망의 실제 이용 속도는 대부분 최대속도보다 낮은 속도로 이용되는 것으로 조사되었으며, 이용 속도가 가장 낮은 시간은 출퇴근 시간대로 조사되었다. 조사된 출퇴근 시간대의 이용속도를 기반으로 접근성 분석을 수행한 결과 평균 37.94분이 소요되는 것으로 분석되었으며, 법정허용 속도에서는 15.70분으로 분석되어 약 2.4배 가량 과소평가되고 있는 것으로 나타났다. 이를 법정허용속도에 의한 접근성과 실제 이용속도 접근성 비율을 지연계수라 정의하고 분석을 수행한 결과 서울시의 지연계수는 2.44로 분석되었다. 행정구역별로 지연계수를 분석한 결과 한강을 중심으로 북쪽이 높고 남쪽이 상대적으로 낮은 지연계수를 보이는 것으로 분석되었다. 이를 도로밀도에 따른 통행량으로 비교한 결과 도로밀도에 따른 통행량이 증가할수록 지연계수가 감소하는 것으로 나타났다. 이는 통행량이 많다고 하여 반드시 이동시간이 증가하지 않는 것으로 볼 수 있으며, 이동시간의 증가를 유발하는 인자를 파악하기 위해서 향후에는 도로체계의 형상, 도로 폭, 신호체계 등 고도화된 정보를 기반으로 파악해야 할 것으로 보여진다.

• 통합자연과학논문집
• /
• 제7권1호
• /
• pp.57-61
• /
• 2014

This study measured the stream data from the several sensors, and stores the database in MapReduce framework environment, and it aims to design system with the small performance and cluster analysis error rate through the KMSVM algorithm. Through the KM-SVM algorithm, the cluster analysis effective data was used for U-health system. In the results of experiment by using 2003 data sets obtained from 52 test subjects, the k-NN algorithm showed 79.29% cluster analysis accuracy, K-means algorithm showed 87.15 cluster analysis accuracy, and SVM algorithm showed 83.72%, KM-SVM showed 90.72%. As a result, the process speed and cluster analysis effective ratio of KM-SVM algorithm was better.