• 한국산학기술학회논문지
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• 제14권10호
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• pp.4665-4671
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• 2013

엔진 설치 시스템은 차량의 NVH 성능에 매우 중요한 시스템 이다. 차량의 NVH 성능은 공회전 진동(Idle Vibration), 엔진 쉐이크(Engine Shake) 시동 진동(Key ON/OFF Vibration), 변속 진동(Gear Shift Vibration) 등 다양한 이론이 존재한다. NVH 성능 개선을 위해 이러한 이론들에 대한 실제적 최적화가 필요하며, 특히 최적의 엔진 설치 위치와 강성을 찾아내는 것이 매우 중요하다. 또한 효과적인 NVH 성능 개선을 위하여 차량개발 프로세스 측면에서 제약조건과 한계가 있는 사후 조정보다는 개발 초기에 최적화가 필요하다. 본 논문에서는 엔진 설치 시스템 관련 여러 이론에 대한 최적화 해석과 파워 트레인의 엄격한 모드 분리와 토크롤축(Torque Roll Axis), 탄성롤축(Elastic Roll Axis) 사이의 각도를 최소화 하는 다양한 시뮬레이션 케이스(Simulation Case)와 FE-모드를 개발초기에 수행하여 다중 최적화 분석을 함으로서 최적의 엔진 설치 위치와 강성을 찾아내어 NVH 성능을 개선하였다.

• 한국운동역학회지
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• 제14권2호
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• pp.41-55
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• 2004

This study analyzed snatch technique in weight-lifting performed by female gold, silver, and copper medalists at the 75kg level in the 2002 Pusan Asian Games and obtained the following conclusions. 1. KSH used more extensor in the waist than those in ankles, knees, or hip joints during the second pull, So further training is required to manifest both each of joints and waist extensor effectively and thus for the line from shoulders through barbell to hip joints to form a smooth vertical pattern. 2. Contrary to those in other countries, Korean athlete KSH tended to be swift in starting but slow in the second pull section, showing less effectiveness in movement during the second pull; therefore, they must try to exert a swift movement in lockout. 3. KSH showed slowdown in the speed, which was a factor interfering with performance during second pull, despite the great maximum speed of moving barbell. It is important to use barbell sufficiently not to reduce the speed of vertical movement but rather to keep the speed increasing. 4. KSH, who kept doing inefficient movements such as failure to perform swift lockout after lifting the heel at the maximum angle of lower limbs, needs to reduce this meaningless extension of ankles, knees, or hip joints to exert energy effectively.

• 한국컴퓨터정보학회논문지
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• 제12권6호
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• pp.131-137
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• 2007

전파가 미치지 않는 3차원 지형에서의 음영공간을 항공기가 안전하게 목적지까지 비행하는 최단 경로를 구하고자 하는 것이다. 여기서 비교적 넓은 음영공간을 다각형 형태의 볼록 다각형으로 분할하고, 분할된 볼록 다각형 내에서는 가중치 값에 따라 중간목적지까지의 경로를 찾고, 그 중간목적지를 시작점으로 하여 인접한 다각형에서 다시 목적지를 찾아가는 과정을 분할된 다각형 내에서 반복해서 최종 목적지까지의 최단 경로를 찾아가는 방법을 제안하였다. 구현은 3차원 실지형 상에서 전파가 미치지 않는 음영공간상에 Graph Growth 알고리즘의 임계값을 적용한 수정된 알고리즘을 이용하여 최단 경로를 탐색하였다. 실험에 의해 본 논문에서 제안한 방법이 효과적인 비행 궤적을 생성하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권2호
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• pp.140-146
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• 2013

In this paper, we describe a vision sensor-based driving algorithm for indoor automatic guided vehicles (AGVs) that facilitates a path tracking task using two mono cameras for navigation. One camera is mounted on vehicle to observe the environment and to detect markers in front of the vehicle. The other camera is attached so the view is perpendicular to the floor, which compensates for the distance between the wheels and markers. The angle and distance from the center of the two wheels to the center of marker are also obtained using these two cameras. We propose five movement patterns for AGVs to guarantee smooth performance during path tracking: starting, moving straight, pre-turning, left/right turning, and stopping. This driving algorithm based on two vision sensors gives greater flexibility to AGVs, including easy layout change, autonomy, and even economy. The algorithm was validated in an experiment using a two-wheeled mobile robot.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.91-94
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• 2005

With increasing demands for large-scale micro-optical components in the field of digital display, the establishment of large-scale fabrication technology fur polymeric patterns has become a priority. The starting point of any polymer replication process is the mold, and the mold often has flat surface. However, It is very hard to replicate large-scale micro patterns using the flat mold, because the cost of large-scale flat mold was very high, and some uniformity and releasing problems were often occurred in large scale flat molding process. In this study, a UV roll imprinting system to overcome the financial and fabrication issues of large-scale pattern replication process was designed and constructed. As a practical example of the system, a lenticular lens with radius of curvature of $223{\mu}m$ and pitch of $280{\mu}m$, which was used to provide wide viewing angle in projection TV, was designed and fabricated. The roll stamper was fabricated using direct machining process of aluminum roll base. Finally, the shape accuracy and uniformity of roll imprinted lenticular lens sheet were measured and analyzed.

• 복식문화연구
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• 제23권3호
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• pp.512-522
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• 2015

The aim of this study was to investigate the change in women's somatotype with aging. The subjects were 1,123 women aged 40~69. Their anthropometric data were from the 6th Size Korea. The data were analyzed by factor analysis and cluster analysis. Seven factors were extracted: body mass, body length, back shoulder, arm length factor, front interscye factor, body rise factor, and shoulder angle. The upper body types of middle-aged and elderly women were classified into five types: skinny, short stout body type with forward posture, composite, tall & full body type, and short & skinny. The skinny and composite body type appeared more often than the short stout body type in the early 40s of Korean women. Starting in the mid-50s, composite body type was less often found. However, the number of women with short stout body type increased. In the 60s, the number of women with short stout and tall & full body types decreased. These results reveal that the body types of middle-aged and elderly women changed with some pattern with aging. And women in their early 40s, mid-50s, and 60s women had different body shapes and postures.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.49.3-49.3
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• 2009

Geostationary Ocean Colour Imager (GOCI) is the first ocean color instrument that will be operating in a geostationary orbit from 2010. GOCI will provide the crucial information of ocean environment around the Korean peninsula in high spatial and temporal resolutions at eight visible bands. We report an on-going development of imaging and radiometric performance prediction model for GOCI with realistic data for reflectance, transmittance, absorption, wave-front error and scattering properties for its optical elements. For performance simulation, Monte Carlo based ray tracing technique was used along the optical path starting from the Sun to the final detector plane for a fixed solar zenith angle. This was then followed by simulation of red-tide evolution detection and their radiance estimation, following the in-orbit operational sequence. The simulation results proves the GOCI flight model is capable of detecting both image and radiance originated from the key ocean phenomena including red tide. The model details and computational process are discussed with implications to other earth observation instruments.

• 제어로봇시스템학회논문지
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• 제21권7호
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• pp.677-683
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• 2015

This paper proposes a helicopter direction adjustment system using barycenter shift. Most conventional methods for direction adjustment of uniaxial helicopters rely on the angle of inclination of the main rotor. However, the inherent burden of the bearing of the main rotor and serious abrasion of the helicopter using the above methods may results in loss of balance. To decrease abrasion and enhance the barycenter stability, the proposed method was used to shift the barycenter of the helicopter instead of the main rotor for direction adjustment. We set a biaxial ARM on a uniaxial helicopter to adjust the direction of ARM pointing as well as to realize stable direction control when the helicopter loses its balance. The method may enhance the landing safety of helicopters in emergencies. Uniaxial helicopters can be controlled under any environment by adjusting the motor parameters of the ARM which is dependent on the center of mass using neural network. The experiment results show that the helicopter can return to the starting position quickly under the external disturbance.

• Journal of Power Electronics
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• 제2권2호
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• pp.146-153
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• 2002

this paper presents an implementation of digital control system of speed sensorless for Reluctance Synchronous Motor (RSM) drives with direct torque control (DTC). The problem of DTC for high-dynamic performance RSM drive is generating a nonlinear torque due to a saturated nonlinear inductance curve with various load currents. The control system consists of stator flux observer, compensating inductance look-up table, rotor position/speed/torque estimator, two hysteresis band controllers, an optimal switching look-up table, IGBT voltage source unverter, and TMS320C31 DSP controller. The stator flux observer is based on the combined voltage and current model with stator flux feedback adapitve control that inputs are the compensated inductances, current and voltage sensing of motor terminal with estimated rotor angle for wide speed range. The rotor position is estimated rotor speed is determined by differentiation of the rotor position used only in the current model part of the flux observer for a low speed operation area. It does not requrie the knowledge of any montor paramenters, nor particular care for moter starting, In order to prove the suggested control algorithm, we have simulation and testing at actual experimental system. The developed sensorless control system is showing a good speed control response characterisitic result and high performance features in 20/1500 rpm with 1.0Kw RSM having 2.57 ratio of d/q reluctance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.112-116
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• 2002

A sensorless control strategy for permanent magnet synchronous motors is presented in this paper. A speed control scheme based on the measurement and observation of stator current, voltage. and flux vector is proposed. Two phase voltages and two stator currents are measured and processed in discrete form in DSP. The rotor position and speed are estimated through the stator flux and its derivative estimation. Flux and its derivative are calculated in the stationary reference frame and used to estimate the speed and position. The rotor position angle is then used in a microcontroller to produce the appropriate stator current command signals for the hysteresis current controller of the inverter. The closed-loop speed control has been shown to be effective from standstill to rated speed. Moreover, a flux drift problem caused by the integration can be eliminated so that a stable sensorless starting and running operation can be achieved. Computer simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.