• 대한기계학회논문집
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• 제19권7호
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• pp.1597-1603
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• 1995

A prediction model on forward slip has been developed for presetting rolling speed of each finish mill stand in the continuous hot strip roduction. Those factors such as neutral point, friction coefficient, volume fractions undergoing width spread, shape of deformation zone at each side of entry and delivery of the rolls were taken into account. To reduce the speed unbalance between adjacent stands a refining method of adjusting friction coefficient has also been developed. On-line application of the model showed a good agreement in rolling speeds between the predictions and the actual measurements, and gave an outstanding improvement in the travelling stability of strip passing through the finishing mill train.

• 전력전자학회논문지
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• 제5권5호
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• pp.451-458
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• 2000

이중여자 유도기를 계통선 연계형 풍력발전 시스템에 적용할 때, 고정자는 계통선에 그리고 회전자는 제어 시스템에 연결된다. 이때 고정자에는 일정전압과 주파수가 걸리기 때문에, 고정자측에 는 거의 일정한 고정자 자속값을 갖는다. 또한 고정자 자속을 기준으로 고정자 전류와 회전자 전류를 이용하여 슬립각을 추정하고, 이를 이용하여 고정자측에 출력되는 전력을 제어한다. 제안한 알고리즘의 타당성을 검증하기 위해 컴퓨터 시뮬레이션과 실험을 통하여 이를 입증한다.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.59-67
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• 2014

A numerical model and a controller of Active Front wheel Steer (AFS) system are designed in this study. The AFS model consists of four sub models, and the AFS controller uses sliding mode control and PID control methods. To test this model and controller an Integrated Dynamics Control with Steering (IDCS) system is also designed. The IDCS system integrates an AFS system and an ARS (Active Rear wheel Steering) system. The AFS controller and IDCS controller are compared under several driving and road conditions. An 8 degree of freedom vehicle model is also employed to test the controllers. The results show that the model of AFS system shows good kinematic steering assistance function. Steering ratio varies depends on vehicle velocity between 12 and 24. Kinematic stabilization function also shows good performance because yaw rate of AFS vehicle tracks the reference yaw rate. IDCS shows improved responses compared to AFS because body side slip angle is also reduced. This result also proves that AFS system shows satisfactory result when it is integrated with another chassis system. On a split-m road, two controllers forced the vehicle to proceed straight ahead.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.76-85
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• 1997

The understeer characteristics of four wheel steering system(4WS system) in a high speed region have a negative effect upon the yaw velocity, leading to a decrease in the handling ability of vehicle. As a result, even if the side slip angle of vehicle can be kept up a minimum, a driver must compensate a decrease in yaw velocity by increasing the steering wheel angle in order to track the desired vehicle path. In this study, to keep the side slip angle of vehicle at zero and achieve a suitable yaw velocity in vehicle motion, a full active 4WS system(FA 4WS system) with actively steerable front and rear wheels is presented based on a nonlinear vehicle model and a model following control of yaw velocity. And the analysis results show the fat that, besides the excellent stability of vehicle, the FA 4WS system is able to realize better handling performance of vehicle than the previous 4WS systems in the high speed region.

• 한국항공우주학회지
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• 제42권12호
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• pp.997-1003
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• 2014

무인항공기의 자동이착륙을 성공적으로 수행하기 위해서는 자동 지상활주 제어는 반드시 설계되어야 하는 중요한 부분이다. 이러한 지상활주 제어기를 설계하기 위해서는 정확하고 신뢰도 높은 착륙장치 모델은 반드시 필요하다. 본 연구에서는 착륙장치 모델링을 완성하기 위해서 특별히 착륙장치 측력 모델링을 수행하였다. 조향각 명령을 포함한 Cornering Angle을 계산하여 측력을 모델링하였다. 그리고 모델링된 착륙장치 모델을 포함한 비선형 6자유도 시뮬레이션 환경을 이용하여, 항공기의 바람벡터 방향인 Course Angle 오차를 해소하기 위한 전륜 조향(Nose Wheel Steering)과 러더 조향(Rudder Steering)을 동시에 이용하는 자동 지상활주 제어기를 설계하였다. 설계된 지상활주 제어기를 동일하게 적용하여, 착륙장치 모델을 포함한 시뮬레이션 결과와 실제 무인기를 이용한 자동 지상활주 시험 결과를 비교하였고, 이로써 착륙장치 측력 모델링과 지상활주 제어기의 정확성을 입증하였다.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.927-935
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• 2005

In the present paper the dynamics of the structure varying multibody systems caused by stick-slip motion with two-dimensional dry friction are analyzed. The methods to determine friction force both in stick and slip states are described. The direct method of considering the wagon bogie system as a structure varying system was used to consider two dimensional friction at the wheelset-side frame connection. The concept of friction direction angle used to determine the friction force components of two-dimensional dry friction both in the stick and slip motion states was used. A speed depended friction coefficient was used and described approximately by hyperbolic secant function. All switch conditions were derived and friction forces both for stick and slip states. Some simulation results are provided.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.107-117
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• 1998

As the traffic congestion and parking problems in urban areas are increased the tall and narrow commuter vehicles have interested as a means to increase the utilization of existing freewa- ys and parking facilities. However, in hard cornering those vehicles could reduce stability against overturning compared to conventional vehicles. This tendency can be mitigated by tilting the body toward the inside of the turn. In this paper those tilting vehicles are considered in which at speed at least, the tilt angle is controlled by steering the front wheels. In other word, if the driver turns the steering wheel the tilt controller automatically steers the road wheel to tilt the body inside of the turn. Also, the dynamic tilting vehicle model with tire slip angles is constructed by adding the roll degree of freedom. Finally, through computer simulation the behaviors of the tilting vehicles are investigated.

• 소성∙가공
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• 제8권6호
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• pp.583-590
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• 1999

New forward slip model has been developed for the precise prediction of rolling speed in the hot strip finishing mill. Besides those influential factors such as neutral point, work roll diameter, friction coefficient, bite angle and the thickness at each side of entry and delivery of the rolls, roll torque was specifically taken into account in this study. To consider the effect of width change on forward slip, calibration factors obtained from rolling torque has been added to new prediction model and refining method has also been developed to reduce the speed unbalance between adjacent stands. The application of the new model showed a good agreement in rolling speeds between the predictions and the actual measurements, and the standard deviation of prediction error has also been significantly reduced.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.335-338
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• 2007

공대공미사일의 경우 초음속 하에서 고 기동성을 얻기 위하여 고받음각 능력이 요구되어진다. 옆 미끄러짐이 없는 대칭형 세장형 몸체의 경우라도 비대칭 와류는 생성된다. 이러한 비대칭 와류는 불필요한 측력 및 요잉모멘트를 발생시키고 이는 곧 방향 안전성을 저하시킨다. 본 연구는 전산해석을 통하여 초음속유동하에서 세장형 몸체 주변에 발생되는 비대칭와류 모사를 실시하였으며 비대칭 와류의 모사를 위해 선두부에 Bump를 장착하였다. 전산해석 결과 세장형 몸체 주변에 발생하는 비대칭와류를 모사 할 수 있었다.

• 자동차안전학회지
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• 제5권1호
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• pp.62-68
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• 2013

This paper describes development of 4 Wheel Drive (4WD) Electric Vehicle (EV) based driving control algorithm for severe driving situation such as icy road or disturbance. The proposed control algorithm consists three parts : a supervisory controller, an upper-level controller and optimal torque vectoring controller. The supervisory controller determines desired dynamics with cornering stiffness estimator using recursive least square. The upper-level controller determines longitudinal force and yaw moment using sliding mode control. The yaw moment, particularly, is calculated by integration of a side-slip angle and yaw rate for the performance and robustness benefits. The optimal torque vectoring controller determines the optimal torques each wheel using control allocation method. The numerical simulation studies have been conducted to evaluated the proposed driving control algorithm. It has been shown from simulation studies that vehicle maneuverability and lateral stability performance can be significantly improved by the proposed driving controller in severe driving situations.