• 한국정밀공학회지
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• 제21권12호
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• pp.84-91
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• 2004

A CCD camera with a laser stripe was applied to realize the automatic weld seam tracking in GMAW. It takes relatively long time to process image on-line control using the basic Hough transformation, but it has a tendency of robustness over the noises such as spatter and arc tight. For this reason, it was complemented with adaptive Hough transformation to have an on-line processing ability for scanning specific weld points. The adaptive Hough transformation was used to extract laser stripes and to obtain specific weld points. The 3-dimensional information obtained from the vision system made it possible to generate the weld torch path and to obtain the information such as width and depth of weld line. In this study, a neural network based on the generalized delta rule algorithm was adapted for the process control of GMA, such as welding speed, arc voltage and wire feeding speed.

• Journal of Advanced Marine Engineering and Technology
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• 제27권6호
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• pp.759-766
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• 2003

The amount of container freight continuously has been increased. and the low efficiency of container crane causes jamming frequently in transportation and cargo handling at port. The conventional control techniques based on a mathematical model are not well suited for dealing with ill-defined and uncertain systems. Recently. Fuzzy control has been successfully applied to a wide variety of practical problems as robots. automatic train operation system. etc. In this paper. a fuzzy controller for container crane is proposed to accomplish a design of improved control system for minimizing the swing motion at destination. In this scheme a mathematical model for the system is obtained in state space form. Finally. to exhibit the tracking performance and robustness of the proposed controller. computer simulations were carried out with various references, parameter variations and disturbances.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.44-49
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• 2001

For minimum phase systems, the conventional fuzzy logic controllers (FLCs) use the error and the change-of-error as fuzzy input variables. Then the control rule table is a skew symmetric type, that is, it has UNLP (Upper Negative and Lower Positive) or UPLN property. This property allowed to design a single-input FLC (SFLC) that has many advantages. But its control parameters are not automatically adjusted to the situation of the controlled plant. That is, the adaptability is still deficient. We here design a single-input direct adaptive FLC (SDAFLC). In the AFLC, some parameters of the membership functions characterizing the linguistic terms of the fuzzy rules are adjusted by an adaptive law. The SDAFLC is designed by a stable error dynamics. We prove that its closed-loop system is globally stable in the sense that all signals involved are bounded and its tracking error converges to zero asymptotically. We perform computer simulations using a nonlinear plant and compare the control performance between the SFLC and the SDAFLC.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.193-198
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• 2009

Generally a TV broadcast video of ball sports is composed from those of multiple cameras strategically mounted around a stadium under the supervision of a master director. The director decides which camera the current view should be from and how the camera work should be. In this paper, such a decision rule is based on the 3D location of ball which is the result of multi-view tracking. While current TV sports broadcast are accompanied with professional cameramen and expensive equipments, our system requires few video cameras and no cameraman. The resulted videos were stable and informative enough to convey the flow of a match.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.7-10
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• 1998

Because of simple control algorithm and easy implementation, the conventional PI controller has been widely used in industrial application. But, it is very difficult to find the optimal PI control gain. Therefore, in improperly tuned PI controller or parameter variation, to obtain optimal performance, the novel PI controller, which consist of conventional PI controller and 4-rule based fuzzy logic, are presented in this paper. The novel PI controller which exhibits a stabilizing effects on the closed-loop system, has good robustness regarding the improperly tuned PI controller or parameter variation. The simulations are performed to verify the capability of proposed control method on induction motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.58-61
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• 1996

For a class of single-input single-output continuous-time nonlinear systems, a multilayer neural network-based controller that feedback-linearizes the system is presented. Control action is used to achieve tracking performance for a state-feedback linearizable but unknown nonlinear system. The multilayer neural network(NN) is used to approximate nonlinear continuous function to any desired degree of accuracy. The weight-update rule of multilayer neural network is derived to satisfy Lyapunov stability. It is shown that all the signals in the closed-loop system are uniformly bounded. Initialization of the network weights is straightforward.

• 한국정보과학회 언어공학연구회:학술대회논문집(한글 및 한국어 정보처리)
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• 한국정보과학회언어공학연구회 2020년도 제32회 한글 및 한국어 정보처리 학술대회
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• pp.518-523
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• 2020

본 논문에서는 목적 지향 대화 시스템을 위한 대화 상태 추적 시스템과 사용자 시뮬레이터를 설계 및 제안한다. 사용자 시뮬레이터는 작성된 대화 상태 추적 시스템을 평가하기 위한 용도로 사용된다. 본 논문에서 제안하는 대화 상태 추적 시스템은 대화 기록과 함께 사전에 학습된 대화 기록 및 규칙/통계 기반 추론 시스템의 추론 결과를 입력으로 받는다. 그리고 입력된 발화 기록 중 마지막 사용자 발화의 사용자 목표와 개체명 그리고 다음 시스템 발화의 화행을 추론한다. 또한, 작성된 대화 상태 추적기의 성능을 평가하고 분석하기 위해, 주어진 환경에서 시스템과 대화를 수행하며 대화 시스템의 성능을 평가하는 사용자 시뮬레이터를 구현 및 적용하였다. 본 연구에서 수행된 실험과 분석을 통해, 규칙 및 통계 기반의 기반 시스템을 이용해 목표 시스템의 성능 개선이 가능함을 보인다. 또한, 제안하는 사용자 시뮬레이터는 규칙과 통계를 이용해 평가 코퍼스 없이 여러 상황에 대해 대화 시스템의 성능을 평가할 수 있다.

• 한국수자원학회논문집
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• 제32권5호
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• pp.579-591
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• 1999

저수지의 시스템 조작은 수자원 계획 또는 관리 측면에서 저수지 설계 뿐 아니라 운영 기준을 마련하기 위해서 필수적이다. 한편 수자원 체계가 확장되고 복잡해짐에 따라 시스템 조작기법 또한 진보적인 방법이 요구된다. 이에 따라 다양한 기법이 도입되어 시스템 조작에 적용되어 왔다. 본 연구에서는 국내에서 최대 규모인 한강수계 저수지 계통의 시스템 조작에 최적제어이론인 선형추적 모형을 적용하여 이용 가능성을 평가한다. 이때 한강 수계 저수지 계통은 수력발전 사용수량을 통하여 하류에 용수를 공급함으로써 수도권의 용수공급을 담당하고 있다. 이에 이수측면의 수자원 이용을 극대화하기 위해서 수력발전 최대화에 조작 목적을 두고 용수공급은 제약조건으로 하여 우선적으로 공급하도록 선형추적 모형을 설계하고 최적 제어율의 유도 및 적용을 통하여 저수지 조작을 수행한다. 이때 조작은 화천댐, 소양강댐, 춘천댐, 의암댐, 청평댐, 충주댐, 팔당댐 등 주요 7개 댐을 포함하고 월단위로 21년간을 수행한다. 그리고 조작결과는 수력발전과 용수공급 및 보장수량 측면에서 분석되고 조작 연산 효율성이 검토된다.

• Journal of Communications and Networks
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• 제11권2호
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• pp.134-147
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• 2009

Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.

• 전기학회논문지
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• 제57권3호
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• pp.518-526
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• 2008

The fuzzy self-tuning PID controller is a PID controller with a fuzzy logic mechanism for tuning its gains on-line. In this structure, the proportional, integral and derivative gains are tuned on-line with respect to the change of the output of system under control. This paper deals with two types of fuzzy self-tuning PID controllers, rule-based fuzzy PID controller and learning fuzzy PID controller. As a medical application of fuzzy PID controller, the proposed controllers were implemented and evaluated in a laparoscopic surgery robot system. The proposed fuzzy PID structures maintain similar performance as conventional PID controller, and enhance the position tracking performance over wide range of varying input. For precise approximation, the fuzzy PID controller was realized using the linear reasoning method, a type of product-sum-gravity method. The proposed controllers were compared with conventional PID controller without fuzzy gain tuning and was proved to have better performance in the experiment.