• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.923-928
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• 2003

This paper presents the motion control of a mobile robot with arc sensor for lattice type welding. Its dynamic equation and motion control method for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven along a straight line or comer. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider controls. For the torch slider control, the proportional integral derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the comer with range of $90^{\circ}$ constrained to the welding speed. The proposed control methods are proved through simulation results and the results have proved that the mobile robot has enough ability to apply the lattice type welding line.

• 한국전자통신학회논문지
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• 제14권2호
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• pp.425-432
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• 2019

노즐모양이 터빈의 회전력과 축동력에 미치는 영향을 분석하기 위해, 분자 동력학 시뮬레이션을 수행하였다. 3 개의 파라메타, 노즐모양, 터빈의 회전속도 w, 분자들의 초기 속도 ($V_x,V_y$) 값들을 변화하면서, 시뮬레이션을 수행하여 터빈입구와 출구에서 분자들의 터빈 회전방향으로의 속도를 계산하였다. 이 두 영역에 걸쳐 평균 운동량을 각각 계산하고 그 차이(AMD)를 비교 분석하였다. 사용한 노즐 모양을 대상으로 AMD를 향상할 수 있는 w의 최적의 범위 도출하였으며, 터빈의 축동력 형성에 더 많이 기여할 수 있는 우수한 노즐 모양을 파악하였다.

• 한국진공학회지
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• 제17권3호
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• pp.189-194
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• 2008

플라즈마 진단법 중 손쉽고 구동이 용이한 장점으로 인해 범용 플라즈마 진단 장치로 사용되는 랑뮤어 (Langmuir) 탐침법은 탐침이 직접 플라즈마 내에 삽입됨으로써 플라즈마를 간섭하기 때문에 플라즈마 고유의 특성을 변형시키는 약점이 있다. 본 연구에서는 대기압 아르곤 자유 연소 아크 (free-burning arc)에 삽입된 랑뮤어 탐침에 의한 교란 영향을 고찰하기 위하여 탐침 유무에 따른 열플라즈마 상태를 수치계산 하였고, 온도장과 속도장이 왜곡된 정도를 비교 분석하였다. 열플라즈마를 모델링하기 위하여 열유동장과 전자기장에 관한 두 종류의 지배방정식을 상용 CFD 프로그램과 자체 제작한 서브루틴을 이용하여 연계 계산하였다. 삽입된 탐침에 의해 열플라즈마 온도장은 탐침의 앞뒤에서 모두 플라즈마 축의 수직 방향으로 큰 변화를 나타내는 열적 교란이 발생되었다. 속도장에서는 탐침 선단의 정체 영역과 후단 후류 영역에서 유동 교란이 발생되었으며, 삽입 된 탐침의 영향이 국부적인 것이 아닌 플라즈마 유동장 대부분 영역에 영향을 미침을 확인할 수 있었다. 따라서 탐침법의 신뢰성을 높이기 위해서는 탐침 삽입에 의한 플라즈마의 열유체역학적 교란을 고려해야 한다.

• Journal of Astronomy and Space Sciences
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• 제26권2호
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• pp.229-236
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• 2009

다목적실용위성-5호는 2010년 발사를 목표로 고도 550km의 저궤도에 위치하게 될 것이다. 다목적실용위성-5호의 임무인 고정밀 SAR(Synthetic Aperture Radar) 영상을 처리하기 위해서는 정확한 위성의 위치(20cm) 와 속도(0.03cm/s)가 결정되어야 한다. 이러한 요구 조건은 한국 전자통신연구원에서 개발한 ETRI GNSS Precise Orbit Determination(EGPOD) 소프트웨어로 검증하였다. 0.1Hz 수신 주기의 SAC-C 위성 반송파위상 데이터로 정밀궤도결정을 수행하였다. 이중 주파수 GPS 데이터를 사용하여 수신 선호의 전리층 오차를 대부분 제거하고 이중 차분된 데이터를 생성함으로써 GPS 위성과 수신기의 공통된 시계 오차를 없앴다. 동역학 모델 접근 방법을 이용하였고, Batch Least Square Estimator(BLSE) 필터로 각 데이터 아크(arc) 에 해당하는 위성의 위치와 속도, 대기저항 계수, 태양풍 계수를 추정하였다. 또한 정밀한 동역학 모델을 위하여 모델 되지 않은 부정확한 가속도 항을 보충하는 경험 가속도를 추가하였다. 경험 가속도는 위성의 공전 주기(revolution) 당 한번씩 시선방향(radial), 진행방향(along-track), 수직방향(cross-track)으로 추정하고, 수직방향의 상수 항에 대해서는 해당 데이터 아크에 관하여 부가적으로 추정하였다. 정밀궤도결정 결과 검증을 위하여 EGPOD 소프트웨어에서 얻어진 결과와 JPL에서 제공하는 정밀궤도력(Precise Orbit Ephemeris)을 비교하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.447-452
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• 2004

Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at intermediate strain rate is obtained from the high speed tensile test machine test and at the high strain rate is obtained from the split Hopkinson pressure bar test. Experimental results from both quasi-static and dynamic compressive tests are interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the amount of chromium content.

• 천문학회지
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• 제45권5호
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• pp.117-125
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• 2012

We present $^{12}CO$ J = 2-1 line observations of G54.1+0.3, a composite supernova remnant with a mid-infrared (MIR) loop surrounding the central pulsar wind nebula (PWN). We map an area of $12^{\prime}{\times}9^{\prime}$ around the PWN and its associated MIR loop. We confirm two velocity components that have been proposed to be possibly interacting with the PWN/MIR-loop; the +53 km $s^{-1}$ cloud, which appears in contact with the eastern boundary of the PWN and the +23 km $s^{-1}$ cloud, which has CO emission coincident with the MIR loop. However, we have not found a direct evidence for the interaction in either of these clouds. Instead, we detected an 5'-long arc-like cloud at +15-+23 km $s^{-1}$ with a systematic velocity gradient of ~3 km $s^{-1}$ $arcmin^{-1}$ and broad-line emitting CO gas with widths (FWHM) of ${\leq}7km\;s^{-1}$ in the western interior of the supernova remnant. We discuss their association with the supernova remnant.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1585-1596
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• 2002

The objectives of the present study are to numerically and experimentally investigate the steady and pulsatile flow phenomena in the circular tubes, to quantitatively compare the flow characteristics of Newtonian and non-Newtonian fluids, and to find meaningful hemodynamic information through the flow analysis in the human blood vessels. The particle image velocimetry is adopted to visualize the flow fields in the circular tube. and the results from the particle image velocimetry are used to validate the results of the numerical analysis. In order to investigate the blood flow phenomena in the circular tube. constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids. are determined, and the steady and pulsatile momentum equations are solved by the finite volume prediction. The velocity vectors of the steady and pulsatile flow in the circular tube obtained by the particle image velocimetry arc in good agreement with those by the numerical analysis. For the given mass flow rate. the axial velocity profiles of the Newtonian and the non-Newtonian fluids appear differently. The pulsatile flow phenomena of the Newtonian and the non-Newtonian fluids are quite different from those of the steady flow.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.680-684
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• 1996

Welding systems cannot adapt to changes in the joint geometry which may occur due to a variety of reason. Automatic seam tracking technigue is essential to adjust the welding torch position in real time as it moves along the seam. Automatic tracking system must keep the welding speed constant unrelation to the change of the welding path. Therefore, the information from the laser displacement sensor must be converted into the input to operate the X-Y table and to rotate the desired torch position by proposed algorithm. In this research, laser displacement sensor is used as a seam finder in the automatic tracking system. X-Y moving table manipulated by ac servo motor controls the position and velocity of the torch-and-sensor part. DC motor controls the position and velocity of the torch. X-Y table controls the position of sensor and relative position of torch is controlled by dc motor which is mounted at sensor-and-torch part. Sensor is always ahead of torch to preview the weld line. From the experimental results, we could see the possiblity that the laser displacement sensor can be used as a seam finder in welding process and that the seam tracking system controlled by proposed algorithm is well done.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.209-211
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• 2002

A simple-structured thermal plasma generator for waste gas treatment has been studied. The thermal plasma technology applied to waste treatment has undoubtedly gained high importance owing to its outstanding properties such as flexibility, compact reactor, and clean treatment. Moreover, the thermal plasma generated by ac power has some additional advantages such as simple electrode system and easy maintenance. A prototype 200kW class plasma generator with specifications of 10-30m/sec gas velocity and 3000-5000K temperature on the center just outside of the nozzle has been designed and tested. Case studies on heat transfer, heat flow, velocity distribution, and temperature distribution using a commercial simulation package show lots of flexibility in design. The experimental results from theprototype generator show that the ac thermal plasma is easily controlled by working gas flow once it is ignited. A stabilization condition is discussed with the data from monitoring arc voltage drops with respect to gas flow rate during the test.