• 오토저널
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• 제12권3호
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• pp.21-29
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• 1990

Equipments of passenger cars with modern technologies are gaining their importance. Related with such developments, the four-wheel steering system (4WS) was introduced recently to a few passenger cars in the market. The most important research goal on this new steering system is improvement of active safety, in other words, improvement of handling characteristics of vehicle stability and maneuverability. This paper presents a computer-based study about the effects of 4WS system on the vehicle handling characteristics. A simple bicycle model of 2 d.o.f. is used for the development of four wheel control algorithms of 4WS system, and the rear wheel control strategies are applied to a complex vehicle model of 16 d.o.f. for simulation of selected ISO-driving tests. The 4WS systems, which reduce the sideslip angle at the mass center of vehicle to almost zero, show much improved handling characteristics compared to that of the conventional 2WS system. These 4WS systems, however, result in vehicles with eigen-steer characteristics of extreme understeer behaviour.

• Ocean Systems Engineering
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• 제1권4호
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• pp.297-315
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• 2011

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag profile, through-body tunnel thrusters have become a popular addition to modern AUV systems. The effect of forward vehicle motion and sideslip on these types of thrusters is not well understood. In order to characterize these effects and to adapt existing tunnel thruster models to include them, an experimental system was constructed. This system includes a transverse tunnel thruster mounted in a streamlined AUV. A 6-axis load cell mounted internally was used to measure the thrust directly. The AUV was mounted in Memorial University of Newfoundland's tow tank, and several tests were run to characterize the effect of vehicle motion on the transient and steady state thruster performance. Finally, a thruster model was modified to include these effects.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.165-172
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• 2000

The VDC(Vehicle Dynamic Control) is a control system whose target is to improve stability of a vehicle under lateral motion. A lateral vehicle motion, especially on a slippery road, can lead to a hazardous situation, and the situation can even worsen by the driver`s inappropriate response. In this paper, two VDC systems, a fuzzy-based controller and an LQR-based controller have been developed. The controllers take as input the yaw rate and the sideslip angle of either body or rear wheel, and they yield the direct yaw moment signal by which the vehicle can gain stability during cornering. Simulations have been conducted to evaluate the performance of the control system. The results indicated that the controllers can successfully improve vehicle stability under potentially dangerous driving conditions.

• 한국항공우주학회지
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• 제41권9호
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• pp.708-713
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• 2013

한국항공우주연구원(KARI)은 고고도 전기추진 장기체공 무인기(EAV-3)를 개발하고 있는 중 이다. 우선 고고도 상승 기술 시연을 위한 축소형 비행체 EAV-2H를 개발하였고 EAV-2H로 초도 비행시험을 수행한 결과 측풍에 대한 방향 안정성 및 조종성의 향상이 요구되므로 Advanced Aircraft Analysis(AAA)를 이용한 수직 꼬리날개와 방향타의 재설계를 진행하였다. 방향 조종성을 개선하기위해 방향타의 크기를 기존의 평균 방향타 시위대 수직 꼬리날개 시위 $C_r/C_v(%)=30$을 $C_r/C_v(%)=60$로 늘려 EAV-2H가 가지는 측풍에 대한 방향 조종성(${\beta}(deg)=25^{\circ}$, $v_1(m/sec)=3.54$)을 개선하였다. 또한, 측풍에 의해 발생하는 측력(side force)의 영향을 최소화하기위해 EAV-2H의 수직미익 크기를 기존 대비 15% 줄여(최소한의 방향 안정성 확보, $Cn_{\beta}=0.0588rad^{-1}$), $C_{y_{\beta}}$는 15% $C_{y_r}$는 22% 감소시킴으로써 측풍이 EAV-2H에 미치는 영향을 최소화 하였다. 설계된 EAV-2H의 꼬리날개의 성능은 비행 시험을 통해 검증하였고 그 결과를 적용하여 고고도 장기체공 전기추진 무인기(EAV-3)의 꼬리날개를 설계하였다.

• 한국자동차공학회논문집
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• 제20권6호
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• pp.126-131
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• 2012

Tire force is one of important parameters which determine vehicle dynamics. However, it is hard to measure tire force directly through sensors. Not only the sensor is expensive but also installation of sensors on harsh environments is difficult. Therefore, estimation algorithms based on vehicle dynamic models are introduced to estimate the tire forces indirectly. In this paper, an estimation system for estimating lateral force and states is suggested. The state-space equation is constructed based on the 3-DOF bicycle model. Extended Kalman Filter, Unscented Kalman Filter and Ensemble Kalman Filter are used for estimating states on the nonlinear system. Performance of each algorithm is evaluated in terms of RMSE (Root Mean Square Error) and maximum error.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2151-2156
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• 2003

The distinguishing features of flows at high angles of attacks are caused by the generation of free shear layers at sharp leading edges, by separation of the viscous layers from the surfaces of wings and bodies and by the flow in the wakes of the wings and bodies. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack($15^{\circ}$, $20^{\circ}$, $25^{\circ}$, $30^{\circ}$) and six measuring sections(30%, 40%, 50%, 60%, 70%, 80%) of chord length. Distributions of time-averaged velocity vectors and vorticities over the delta wing model were compared along the chord length direction. Highly swept leading edge extension(LEX) applied to delta wings has greatly improved the subsonic maneuverability of contemporary fighters. High-speed CCD camera which made it possible to acquire serial images is able to get the detailed information about the flow characteristics occurred on the delta wing. Especially quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarity the significance of the LEX existence.

• 한국전산유체공학회지
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• 제17권3호
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• pp.18-24
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• 2012

The aerodynamic performance of the pantograph on a high speed train was compared for different pantograph covers which are designed to block the aero-acoustic noise from the pantograph. For the study, two types of cover are designed: wedge and cone types. The lift force of pantograph with cover was compared with the force of pantograph only. The comparison clarified that the cone type cover increases the sideslip angle of the flow and decreases the lift force considerably. However, the wedge type cover changes the flow direction upward and increases the lift force of the pan head. This increment of lift force compensates the decrement of lift force caused by the blocking of the flow into the pantograph lower frame due to cover. Therefore, in case of the wedge type cover, the overall lift force changes slightly compared with the cone type cover.

• 한국항공우주학회지
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• 제30권4호
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• pp.38-43
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• 2002

본 연구에서는 항공기 날개 표면에서의 공력 하중 분포를 측정하는 풍동 시험 및 모형 설계와 제작에 대한 연구를 수행하였다. 모형 날개에는 총 447개의 압력공을 표면에 수직하게 제작하였으며, 날개 내부에 설치한 압력 tube를 통해 모형 내부에 설치된 총 8개의 EPS modules에 연결하여 PSI-8400 system을 사용 압력 분포를 측정하였다. 풍동 시험은 국방과학연구소 아음속풍동을 사용 50m/sec에서 정속모드로 수행하였다. 시험은 하중분포 예측을 위해 받음각과 옆미끄럼각 변위, 플랩 및 외부장착물 설치에 따른 날개에서의 하중분포 측정을 위해 수행하였다. 본 시험 결과로 항공기 날개 구조 최적 설계 자료로의 활용 및 전산유체역학의 결과 검증에 활용 할 수 있을것으로 판단된다.

• 한국군사과학기술학회지
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• 제23권6호
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• pp.639-649
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• 2020

Air data systems measure airspeed, pressure altitude, angle of attack and angle of sideslip. These measurements are essential for operating flight control laws to ensure safe flights. Since the loss or corruption of air data measurements is considered as catastrophic, a high level of operational reliability needs to be achieved for air data systems. In the case of unmanned air vehicles, failure of any of air data sensors is more critical due to the absence of onboard pilot decision aid. This paper presents design of a dual redundancy air data system and the integration process for an unmanned air vehicle. The proposed dual-redundant architecture is based on two independent air data probes and redundancy management by central processing in two independent flight control computers. Starting from unit testing of single air data sensor, details are provided of system level tests used to meet overall requirements. Test results from system integration demonstrate the efficiency of the proposed process.

• 대한기계학회논문집A
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• 제40권3호
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• pp.317-326
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• 2016

본 연구에서는 한국형 PRT차량의 주행안정성 및 승차감 향상을 위해 현가장치 최적화를 진행하였다. ISO 3888(Double Lane Change Test)를 통하여 주행안정성을 분석하고 ISO 2631-1을 이용하여 승차감 분석을 진행하였다. 이를 통해 주행안정성과 승차감에 대하여 다중반응표면법을 적용하여 현가장치 최적화를 진행하였다. 그 결과 모든 반응함수가 초기설계치보다 모두 개선되는 만족함수의 비율은 3.9 : 6.1이며, 이때 현가장치의 특성은 Stiffness의 경우 S2와 S3 model의 사이 값인 30.68 N/mm과 Damping 계수의 경우 D1 model의 값을 갖는다. 초기설계인 현재 PRT차량의 현가장치와 비교했을 때, 최적화된 PRT 현가장치 설계는 Roll angle와 Yaw rate는 0.37%, Side slip angle은 2.8%, Ride comfort는 5% 향상된다.