• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.391-394
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• 2011

In this paper, the shock angle and effect had been compared with numerical data within supersonic area at an forebody such as missiles or an aircraft. By using supersonic wind tunnel in Seoul National University, The shock position and magnitude were measured in the model of cone shape according to mach number. The experiment had been conducted at mach number 2.0, 3.0, and 3.8. As a result, the shock position and magnitude are different from flow velocity, AOA, and AOS in some cases blockage effect had occurred.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.199-206
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• 2016

Linear motion (LM) ball guides with rolling contact are core units of feed-drive systems. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, the friction force induced from LM ball guides generates heat, which deteriorates positioning accuracy and incurs changes of stiffness and preload. To accurately analyze the effects and apply the results to precision machine design, mathematical modeling of the friction force is required. In this paper, accurate formulation of the friction force due to rolling, viscous, and slip frictions is conducted for LM ball guides. To verify the reliability of the developed friction model, experiments are performed under various assembly, load and velocity conditions. Effects of frictional components are analyzed through the formulated friction model.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2320-2322
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• 2004

전자제어식 미끄럼방지 제동장치 (ABS, Antilock Brake System)는 차량의 급제동시 발생할 수 있는 바퀴의 슬립을 방지하여 차량의 제동거리를 단축시키고 주행 성능을 향상시키는 차량 내 안전장치이다. 지난 몇 년 동안 공압식 제동시스템을 사용하는 대형차량에 적합한 미끄럼방지 제동 제어기를 연구해 왔다. 이 제어기는 바퀴의 슬립율과 그 변화량을 이용한 제어 법칙을 유도하여, 제어 파라미터로 사용하고 있다. 이러한 제어 파라미터의 튜닝에는 맡은 반복적인 실험이 요구된다. 이러한 요구에 부응하기 위하여 차량의 제동을 실시간으로 모사 할 수 있는 HILS (Hardware In-the Loop Simulation) 시스템을 개발, 구축하였다. 개발 HILS는 공압식 브레이크 시스템 및 14 자유도를 가지는 차량 동역학 모델 및 타이어-바퀴 동역학을 소프트웨어 모델로 사용하고, 개발 중인 전자제어식 미끄럼 방지 제동 제어기를 하드웨어로 사용하여, 바퀴속도 센서 신호 모의 장치 및 공압 엑추에이터 모의 신호등의 인터페이스 장치를 사용하여 제동중인 차량의 상태를 실시간으로 시뮬레이션 및 감시할 수 있다. 이 개발 HILS를 이용하여 제동 제어기의 제어 파라미터의 튜닝을 짧은 시간에 성공적으로 끝낼 수 있었을 뿐만 아니라, HILS 실험을 마친 제어기는 미끄럼 방지 제동 시험장에서 실차 주행 시험을 무사히 마침으로써, 개발 기간과 비용을 절감할 수 있는 하드웨어를 이용하는 시뮬레이션의 효용성을 간접적으로 증명하였다.

• Polymer(Korea)
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• v.37 no.5
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• pp.642-648
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• 2013

There is a kind of abnormal noise known to come from the stick-slip mechanism induced by frictional impulses during the sliding of two polymeric plates. In this work, quantitative analysis of abnormal noise is carried out based on experimental results. Some combinations of polymer plates, such as an ABS base-plate contacted to ABS, PP, MIPS, and POM plates, which are well-known materials used in home-appliances, are studied to obtain the best combination of polymer plates in order to reduce the abnormal noise. For the experiments, a rig for the test was set up and a methodology was proposed. In addition, the effects of the surface roughness of the plate, the normal loading force, and the relative sliding speed between the two contact plates were evaluated in order to understand the reason for the abnormal noise. Through this experimental work, the optimal combination of materials was ABS/POM system to reduce the noise in real industrial applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.117-122
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• 2006

Maximum efficiency control scheme in a stator flux-oriented induction motor drive is proposed for minimizing input dc power. Flux level is decreased in steps for searching the minimum input dc power. In addition, Torque equation, slip angular frequency, and decoupling compensation current considering iron loss resistance is used. Simulation and experimental results verify the effectiveness of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.383-386
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• 2005

An integrated analytical model which should have essential dynamics on the longitudinal railway vehicle is developed. The model consists of translational movement, rotational movement, brake actuator, adhesion force between rail and wheel, and brake friction force between wheel and pad. Thus, during the deceleration for stopping, a feedback controller controlling the brake cylinder pressure is designed to improve ride quality and to release friction problems. Through the developed model, the feasibility of controlling the cylinder pressure is verified for the better performances during braking.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.15-18
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• 2006

Recently, experimental visualization of microscale fluid transport has attacted considerable attention in designing microelectromechanical systems. Fluid-surface interactions on hydrophobic and hydrophilic surfaces can play a key role in passively controlling microfluidics. Here we investigate the slip boundary condition depending on the surface characteristics; hydrophilic, hydrophobic wettabilities. Using the micro-PIV, velocity profiles are measured in the glass (hydrophilic), PDMS (hydrophobic) microchannels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.331.1-331
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• 2002

Four degrees of freedom mathematical model is presented to describe the fundamental mechanisms of the disc brake squeal noise. A contact parameter is introduced to describe the coupling between the in-plane and the out-of-plane motions. The friction coeficient including "relative velocity" and ′normal force" can be generally formulated as the form of multiplication with polynominal parameters(${\beta}$, ${\gamma}$). (omitted)

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.228-233
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• 2005

Two-dimensional Stokes flows through a micro channel with a couple of symmetric vertical fins are investigated. At far up- and down-stream from the fins, the plane Poiseuille flow exists in the channel. The slip boundary conditions are applied to take account of the Knudsen number effects. For the analysis, the method of eigen function expansion and collocation method are employed. By the results, the streamline patterns and pressure distributions are shown and the force exerted on the fin and the excess pressure drop due to the fins are determined as functions of the length of the fin and Knudsen number. It may be conjectured that the force and the excess pressure drop are almost independent of the Knudsen number.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.15-20
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• 2012

This study is to propose and develop an integrated dynamics control system to improve and enhance the lateral stability and handling performance. To achieve this target, we integrate an AFS and a 4WS systems with a fuzzy logic controller. The IDCS determines active additional steering angle of front wheel and controls the steering angle of rear wheel. The results show that the IDCS improves the lateral stability and controllability on dry asphalt and snow paved road when double lane change and step steering inputs are applied. Yaw rate of the IDCS vehicle tracks reference yaw rate very well and body slip angle is reduced about by 50%. Response time of the IDCS vehicle is also decreased.