• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.181-187
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• 1996

A frictionless positioning device using cone-shaped active magnetic bearings(AMBs) is developed, which is driven by a brushless DC motor equipped with resolver. The cone-shaped AMB feature that the structure is simple and yet the five d.o.f. rotor motion is controlled by four magnet pairs. A linearized dynamic model, which accounts for the relationship between input voltage and output current in the cone-shaped magnet, is developed and the azimuth motion of the frictionless positioning device is modeled as the second order system. The feedback controller is designed by using linear quadratic regulator with integral action optimal control law so that the cone-shaped AMB system is stabilized and the frictionless positioning device gets the zero steady state. It is observed that the linearized dynamic model is adequate and the frictionless positioning device can achieve the tracking accuracy within the sensor resolution.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.963-968
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• 1990

An iterative learning control scheme for tracking control of a class of uncertain nonlinear systems is presented. By introducing a model reference adaptive controller in the learning control structure, it is possible to achieve zero tracking of unknown system even when the upperbound of uncertainty in system dynamics is not known apriori. The adaptive controller pull the state of the system to the state of reference model via control gain adaptation at each iteration, while the learning controller attracts the model state to the desired one by synthesizing a suitable control input along with iteration numbers. In the controller role transition from the adaptive to the learning controller takes place in gradually as learning proceeds. Another feature of this control scheme is that robustness to bounded input disturbances is guaranteed by the linear controller in the feedback loop of the learning control scheme. In addition, since the proposed controller does not require any knowledge of the dynamic parameters of the system, it is flexible under uncertain environments. With these facts, computational easiness makes the learning scheme more feasible. Computer simulation results for the dynamic control of a two-axis robot manipulator shows a good performance of the scheme in relatively high speed operation of trajectory tracking.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권2호
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• pp.168-176
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• 2015

Due to the reduction in device feature size, transient faults (soft errors) in logic circuits induced by radiations increase dramatically. Many researches have been done in modeling and analyzing the susceptibility of sequential circuit elements caused by soft errors. However, to the best knowledge of the authors, there is no work which has well considerated the feedback characteristics and the multiple clock cycles of sequential circuits. In this paper, we present a new method for evaluating the susceptibility of sequential circuit elements to soft errors. The proposed method uses four Error Propagation Probability Matrixs (EPPMs) to represent the error propagation probability of logic gates and flip-flops in current clock cycle. Based on the predefined matrix union operations, the susceptibility of circuit elements in multiple clock cycles can be evaluated. Experimental results on ISCAS'89 benchmark circuits show that our method is more accurate and efficient than previous methods.

• International Journal of Human Ecology
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• 제1권1호
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• pp.59-77
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• 2000

The purpose of this study was to extend our understanding of the developmental antecedents of delay of gratification in infancy. The first goal was to examine direct effects of one feature of an infants’ temperament and of positive and negative parenting assumed at age one on children’s delay of gratification six months later. The second goal of the study was to test the interactive effect of early infant temperament and parenting on children’s delay of gratification. It was hypothesized that 1) less negative infants at 12 months would delay gratification longer six months later, 2) children of parents who provided more positive and sensitive feedback would delay gratification longer than children with parents who were more negative and less sensitive, and 3) there would be differential prediction of parenting for children who scored high and low in negative emotionality as infants. Toward this end, 81 infants were observed interacting at one year of age with their mothers and fathers during laboratory assessments to obtain measures of parenting and infant negative emotionality. At 18 months of age, the child’s capacity to delay touching attractive objects was measured. The main effects of infant negative emotionality and of mothering on children’s delay of gratification were not detected at standard levels of significance. Differential effects of parenting on children’s delay of gratification for infants with low or high negative emotionality, too, were not detected. However, the anticipated effect of fathering on delay of gratification was found in some analyses, indicating that the more positive fathering children received, the longer they could delay gratification in the laboratory six months later.

• 한국산업보건학회지
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• 제24권1호
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• pp.79-90
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• 2014

Objectives: The aim of this study was to suggest preliminary data for the establishment of communication methodology of asbestos risk, fit for the features of each audiences, by grasping the features of risk communication by each element for each group survey. Methods: For this study, a questionnaire survey has been conducted from May to August 2012 and responses of 617 people including 214 school asbestos managers, 95 asbestos business managers, and 308 general public have been analyzed. Results: The feature by element of risk communication shows that to give information through non-governmental organizations with reliability such as colleges, research institutes, asbestos-related associations, etc among the entire investigated groups, is most effective. Lastly, for stakeholders related to asbestos, the public feedback for governmental asbestos management policy shows that it was considered that there is lack of reality due to comprehension deficit for situation, lack of a system of asbestos general management in the country and lack of policy connectivity among the branches of the government, and between the central government and the local government. However, the general public selected lack of various information disclosure, education, publicity for asbestos and lack of communication with citizens as the biggest problems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.898-901
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• 1988

Up to now, using adaptive control method, Identification deals with system whose entire state variables and prameters are accessible for measurement. In practical situations, all the state variables cannot be measured and it is impossible to directly apply since the parameters of the system are unknown. Therefore, in this paper, using only input-output data, such a model of the system is not available since the parameters of the system are unknown. this leads to the concept of an adptive observer in which both the parameters and the state variable of the system are identified simultaniously. Lyapunov's direct method and Kalman-Yakubovich (K-Y) lemma are employed to ensure the stability of this schemes. The feature is that the signal and adaptive gain which is generated from filter is imposed upon feedback vector and then state variables and the unknown parameters can be identified. To show the usefulness of the proposed schemes, computer simulation result of unknown second-order system shows the effectiveness of the proposed schems.

• 제어로봇시스템학회논문지
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• 제15권9호
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• pp.909-915
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• 2009

This work is to develop a vision system for high precision alignment between upper and lower plates required at the imprinting process of the large LCD flat panel. We compose a gantry-stage that has highly repeated accuracy for high precision alignment and achieves analysis about thermal transformations of stage itself. Position error in the stage is corrected by feedback control from the analysis. This system can confirm alignment mark of upper and lower plates by using two cameras at a time for the alignment of two plates. Pattern matching that uses geometric feature is proposed to consider the recognition problem for alignment mark of two plates. It is algorithm to correct central point and angle for the alignment from the recognized mark of upper and lower plates based on the special characteristics. At the alignment process, revision for error position is performed through Look and Move techniques.

• Journal of Communications and Networks
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• 제4권3호
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• pp.221-229
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• 2002

Adaptability is the most promising feature to be applied in future robust multimedia applications. In this paper, we propose the Direct Algorithm to improve the degree of satisfaction at heterogeneous receivers in multi-layered multicast video environments. The algorithm relies on a mechanism that dynamically controls the rates of the video layers and is based on feedback control packets sent by the receivers. The algorithm also addresses scalability issues by implementing a merging procedure at intermediate nodes in order to avoid packet implosion at the source in the case of large multicast groups. The proposed scheme is optimized to achieve high global video quality and reduced bandwidth requirements. We also propose the Direct Algorithm with a virtual number of layers. The virtual layering scheme induces intermediate nodes to keep extra states of the multicast session, which reduces the video degradation for all the receivers. The results show that the proposed scheme leads to improved global video quality at heterogeneous receivers with no cost of extra bandwidth.

• 한국정보과학회논문지:소프트웨어및응용
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• 제29권7호
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• pp.425-435
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• 2002

본 논문에서는 SOFM기반 신경망 분류기를 이용한 매크로블록 기반 전송률제어 방식을 제안한다. 수학적 왜곡 비트율 모델과 귀환회기 방식을 기반으로 하는 기존의 전송률 제어 방법에 비하여, 제안된 방법은 전송비트 제어용 전역모델을 설정하고 이를 최적으로 제어할 수 있는 SOFM기반 신경망 분류기를 이용하여 영상특성 변화에 적극적인 대처를 할 수 있다. 제안된 전송률 제어 알고리즘은 기존의 MPEG-4 매크로블록 기반 전송률 제어 알고리즘에 비해 전체 연산 복잡도는 비슷하게 유지하면서 피크신호 대 잡음비의 비교에 있어서 0.2 dB ~ 0.6 dB 정도 성능이 우수함을 확인하였다.

• 한국정보통신학회논문지
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• 제11권4호
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• pp.826-832
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• 2007

고속 통신 시스템의 채널 등화에 순환 신경망이 자주 이용되고 있다. 기존의 등화방법은 대부분 시불변 채널을 주로 다루었다. 그러나 이동통신과 같은 현대의 통신환경은 페이딩으로 인하여 시변특성을 갖는다. 본 논문에서는 비선형 시변 시스템에 적용하여 성능이 우수한 결정 피드백 순환신경망을 채널등화기로 이용하며, 또한 채널 등화에 빠른 수렴속도와 우수한 추적성능을 지니는 확장된 칼만필터와 시그마 포인트 칼만필터를 이용한 두 종류의 훈련 알고리즘을 제안한다. 확장된 칼만필터를 이용한 경우 비선형 시스템의 1차 선형화 과정에서 커다란 오차를 유발할 수도 있으며, 이에 대한 대안으로 시그마 포인트 칼만필터를 이용하여 이러한 문제점을 극복할 수 있다.