• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1148-1153
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• 2004

This paper presents the mechanism to increase lateral stability of a mobile robot using an energy stability margin theory. Previous measure of stability used in a wheeled mobile robot has been based on a static stability margin. However, the static stability margin is independent of the height of the robot and does not provide sufficient measure for the amount of stability when the terrain is not a horizontal plane. In this work, the energy stability margin theory, which is dependent on robot's height is used to develop a 2 dof mechanism to increase lateral stability. This proposed mechanism shifts the center of gravity of the robot to the point where the energy stability margin is maximized and overall stability of the robot equipped with this mechanism will be increased.

• KIEE International Transactions on Power Engineering
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• 제4A권3호
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• pp.141-145
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• 2004

FACTS devices, such as the Thyristor Controlled Series Compensator (TCSC) and Static Var Compensators (SVC), can help increase system load margin to improve static voltage stability. In power systems, because of the high cost and the effect value, the optimal placement for FACTS devices must be determined. This paper investigates the use of the series device (SVC) and the parallel device (TCSC) from the point of load margin to increase voltage stability. It considers the sensitivity of load margin to the line reactance and eigenvector of the collapse. The study has been carried out on the IEEE 14 Bus Test System to verify the validity and efficiency of the method. It reveals that incorporation of FACTS devices significantly enhance load margin as well as system stability.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.118-129
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• 2010

A lower-threshold-voltage (LVth) SRAM cell with an elevated cell biasing scheme, which enables to reduce the random threshold-voltage (Vth) variation and to alleviate the stability-degradation caused by word-line (WL) and cell power line (VDDM) disturbed accesses in row and column directions, has been proposed. The random Vth variation (${\sigma}Vth$) is suppressed by the proposed LVth cell. As a result, the LVth cell reduces the variation of static noise margin (SNM) for the data retention, which enables to maintain a higher SNM over a larger memory size, compared with a conventionally being used higher Vth (HVth) cell. An elevated cell biasing scheme cancels the substantial trade-off relationship between SNM and the write margin (WRTM) in an SRAM cell. Obtained simulation results with a 45-nm CMOS technology model demonstrate that the proposed techniques allow sufficient stability margins to be maintained up to $6{\sigma}$ level with a 0.5-V data retention voltage and a 0.7-V logic bias voltage.

• 한국정밀공학회지
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• 제17권3호
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• pp.83-91
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• 2000

During static walking of a quadruped walking robot, stability of the robot depends on whether the projection of the mass center is located within the supporting area that is varying with leg motion and formed by standing legs. In this paper, force margin instead of the mass center was used to determine stability and body-tilting method was used to enhance it. On-line control of body tilting was realized with simple reaction feedback based on force margin of the static walking model of the robot instead of complicated calculation. Model reference on-line control where the model searches stable pose for predefined force margin also gave good walking performance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 추계학술대회 논문집
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• pp.146-154
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• 1991

As the application of robotic systems expand its scope, more research efforts are given in providing mobility to the robotic systems so that they can travel across various paths including those with formidable obstacles such as stairways or rough terrains. Legged locomotion is mainly concerned because the walking motion, like that of animal behavior, has many advantages over wheel type or track type locomotion especially in rough terrain. Walking robot, in general, having a discrete number of legs, have inherently low static stability. Static stability can be increased to a certain degree, by improving walking method, but it has many limitations such as reduced travel speed. A very promising possibility lies in the use of balancing weight, nevertheless its actual implementation is very rare. In this study, a 4-legged walking machine is developed and the static stability margin is increased with the balancing weight. In the future, this robot will be used to take an experiment on the walking in mush terrain.

• 한국항공운항학회지
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• 제15권4호
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• pp.142-147
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• 2007

When the aircraft is developed, several flight tests are performed including stability and controllability, performance and systems, above all the most important part of the flight test is stability test. Stability test is divided into two parts, static stability and dynamic stability. Static stability of the aircraft is typically defined in terms of its initial tendency to return to equilibrium after a disturbance and not included time concept. One of static stability, longitudinal static stability, was addressed here. The longitudinal static stability was studied from the basic theory to the flight test method and also explained data reduction method throughout the flight test. Finally showed how to meet the specifications such as ROC, FAR and MIL-specifications.

• 한국항공우주학회지
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• 제34권6호
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• pp.83-91
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• 2006

현대의 고성능 전투기는 공력성능 및 조종성능의 향상을 위하여 대부분 세로축 방향으로 항공기를 불안정하게 설계하는 정안정성 완화 개념을 채택하고 있다. 비행제어법칙의 설계 작업은 불안정하게 설계된 항공기에 안정성을 부여하고, 주어진 비행임무에 대하여 만족스런 조종성능을 발휘할 수 있도록 비행성능을 조작하는 일련의 과정이다. 세로축 무게중심은 무장형상, 연료상태 및 착륙장치의 위치에 영향을 받으며 항공기 안정성에 많은 영향을 미친다. 따라서 무게중심의 이동은 세로축 안정도 여유에 영향을 미친다. 본 논문에서는 운용 시에 발생 가능한 최대 후방 무게중심에 대해 항공기 안정성을 해석하였고, 비행시험을 통해 최종적으로 검증하였다. 선형해석 항목은 세로축 단주기 모드 특성 및 안정도 여유에 관하여 행하였으며, 비선형 해석 항목은 단주기 모드를 해석하기 위해 세로축 가진 입력에 대한 항공기 응답특성을 분석하였다. 또한, 최대 후방 무게중심에서 수행된 고받음각 비행시험 자료를 제시함으로써 T-50 고등훈련기의 비행 안정성을 제시하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.42-42
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• 2000

This paper concerns an efficient aperiodic static crab walking algorithm for quadruped walking machine in rough terrain. In this algorithm, the requirements for forward stability margin and backward stability margin could be given differently in order to consider the slope of terrain and disturbances resulting from moving velocity. To restrict the searing regions for motion variables, such as moving distances until a leg is lifted or is placed, the standard leg transferring sequence is decided to be that of wave gaits. standard support pattern is also proposed that enables the quadruped to continue forward motion using the standard leg transferring sequence without falling into deadlock.

• 한국산업정보학회논문지
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• 제18권5호
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• pp.19-23
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• 2013

본 논문에서는 고속 데이터 처리용 TCAM(Ternary Content Addressable Memory) 설계를 위하여 6T SRAM cell의 안정성 분석 방법에 대해 기술하였다. TCAM은 고속 데이터 처리를 목적으로 하기 때문에 동작 주파수가 높아질수록 필요 시 되는 CMOS 공정의 단위가 작아지게 된다. 공급 전압의 감소는 TCAM 동작에 불안정한 영향을 줄 수 있으므로 SRAM cell 안정성 분석을 통한 TCAM 설계가 필수적이다. 우리는 6T SRAM의 정적 노이즈 마진(SNM)을 측정하여 분석하였고, TCAM의 모든 시뮬레이션은 $0.18{\mu}m$ CMOS 공정을 사용하여 확인하였다.

• 한국군사과학기술학회지
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• 제9권1호
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• pp.89-98
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• 2006

This paper describes signal attenuation characteristics as splicing the output on LVDT for stability and reliability of switching mechanism, which is developed to use common signal between FLCC and EDFLCC, on T-50 aircraft. The method of test is classified a Pspice simulation and an actual hardware evaluation. The difference of error margin for two methods is 10times, the latter higher. The result in this experiment shows that the signal attenuation as splicing the output on LVDT doesn't affect and the static error margin is 53% for develope the EDFLCC.