• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
• /
• pp.52-56
• /
• 2001

In order to get information on more reliable S-wave attenuation characteristics in the Gyeongsang Basin, local earthquake data compiled during the period of years 1997~2000 are analyzed using spectral smoothing technique. Total 421 seismograms recorded at 12 local stations by 68 earthquakes of local magnitudes equal to or greater than 1.4 are examined. Among them, 155 records with good S/N ratio were analyzed. As results, statistically well constrained attenuation characteristics are fecund. Those are; (1) 0.000158362 < $x_{q}$-value (0.000196474) < 0.000234586, (2) 0.00657 < $x_{s}$-value (0.01061) < 0.01465, and (3) 1158 < Q-value (1383) < 1716, where the upper and low limits are values with 95% confidence level. We obtained remarkably well constrained $X_{s}$-value which has not been determined previously. The results can be used as input data far ground motion computations in earthquake engineering.ing.g.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2013년도 추계학술대회
• /
• pp.209-212
• /
• 2013

본 논문에서 적응적 탐색 영역(Adaptive Search Range)을 이용하여 개선한 제한된 1비트 변환 알고리즘을 제안하였다. 이 변환은 전역 검색 알고리즘 (Full Search Algorithm)을 사용한다. 그러나 이것은 매우 많은 연산량과 복잡도를 가진다. 제안된 알고리즘에서는 각 블록의 탐색범위를 결정하기 위한 움직임 벡터 (Motion Vector)와 함께 제한된 1비트 변환 알고리즘의 제한된 마스크 (Constrained Mask)를 사용한다. 실험결과를 통해 제안된 알고리즘은 움직임 예측의 정확도에 대한 성능을 비슷하게 유지하면서 평균적으로 Search Point의 수를 84% 줄일 수 있음을 보여준다.

• 한국정밀공학회지
• /
• 제27권12호
• /
• pp.48-58
• /
• 2010

In this study, position tracking and force reflection control of a master-slave manipulator which will be used for handling objects contaminated by radioactivity has been addressed. Since available measurements concerning on dynamic motion of the master-slave manipulator are restricted, a simple constrained control structure was suggested. In the consideration of the uncertain dynamic behaviors of the slave manipulator which is dependent upon mass and shape of work pieces grasped and dynamic properties of the environment contacted, a simple structured sliding mode control was suggested to guarantee robustness with respect to parameter uncertainties and external disturbances. The proposed control was applied to a 1-DOF master-slave link system. The control performances were verified along with some computer simulation results.

• 한국정밀공학회지
• /
• 제18권10호
• /
• pp.148-153
• /
• 2001

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping hale been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

• 한국항공운항학회지
• /
• 제15권3호
• /
• pp.6-14
• /
• 2007

In this research, vibration reduction and aeroelastic stability of a composite hingeless rotor hub flexure with viscoelastic constrained layer damping treatment(CLDT) were investigated. The composite flexures with viscoelastic CLDT were applied to hingeless rotor system to improve the in-plane stability of the lead-lag motion causing resonance. The modal test was performed and dynamic properties(natural frequency and loss factor) were acquired. Also, complex eigenvalue analysis(SOLlO7) in the NASTRAN structural analysis module was performed and compared with results of the modal test. To insure aeroelastic stability, damping ratio analyses of the hingeless rotor system with CLDT were accomplished at hovering condition due to collective pitch angle changes. Satisfactory results of increasing structural damping and stability were obtained.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.362-367
• /
• 2003

A new mechanical-electrical hybrid passive dam ping treatment is proposed to improve the performance of structural vibration control. The proposed hybrid passive damping system consists of a constrained layer damping treatment and a shunt circuit. In a passive mechanical constrained layer damping, a viscoelastic material damping layer is used to control the structural vibration modes in high frequency range. The passive electrical damping is designed for targeting the vibration amplitude in the low frequency range. The governing equations of motion are derived through the Hamilton's principle. The obtained mathematical model is validated experimentally. The presented theoretical and experimental techniques provide invaluable tools for controlling the multiple modes of a vibrating structure over a wide frequency band.

• 대한기계학회논문집A
• /
• 제28권11호
• /
• pp.1719-1726
• /
• 2004

Direct drive servovalve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the DC motor. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• 방송공학회논문지
• /
• 제23권6호
• /
• pp.747-759
• /
• 2018

본 논문에서는 실시간 고화질 360 영상 전송을 위해 사용자 시점에 기반한 타일 분할 기법을 적용하고 화질 평가를 위해 360 영상을 가상현실 기기 화면에 표현하는 구현을 설명한다. 사용자 시점에 기반한 고화질 360 영상 전송을 위한 방안으로, 움직임 참조 문제를 해결하기 위한 MCTS (Motion Constrained Tile Sets) 기술과 미리 구성된 타일 정보들을 포함하는 EIS (Extraction Information Sets) SEI (Supplemental Enhancement Information), 타일 정보를 추출해내고 영상을 분할 및 추출해주는 추출기(extractor)를 구현한다. 또한 사용자 시점에 기반한 타일 추출 방법과 추출된 영상을 이용해 가상현실 기기 화면에 표현하는 방법에 대한 구현 내용을 설명한다. 따라서, 제안된 구현물을 기반으로 영상 전송을 수행하면, 사용자 시점 영역의 영상만 전송하여 불필요한 영상 전송을 하지않게 되어 화질 대비 낮은 대역폭의 향상된 영상을 표현할 수 있다.

• 한국해양공학회지
• /
• 제28권4호
• /
• pp.274-279
• /
• 2014

This paper investigates the line dynamic forces connecting tugs and a floater, where the planar motion of the floater is due to the weather criteria during the position keeping of the offshore structure by tugs. The analysis situation consists of the position keeping states for the seabed mooring line connection work of the offshore structure at the offshore site. Specifically, the decision about the tug power capacity for the position keeping is essential and depends on the weather criteria, line characteristics, length of line, etc. The planar motion of the structure is constrained by the interference of the installation vessel's operational range, behavior of the underwater fairlead, and other surrounding structures. In this paper, the tug line forces and planar motion of an offshore structure are summarized dependent on the tug line length and line material characteristics in the states fora given floater draft and weather criteria. The tug line dynamic forces and planar motion evaluated here will be used to determine the proper tug power and clearance of an offshore structure.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집B
• /
• pp.319-324
• /
• 2001

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 corner. 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 experiment has been done to verify the effectiveness of the proposed controllers. These results are shown to fit well by the simulation results.