• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.177-180
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• 1996

The purpose of this paper is to design a robust adaptive control algorithm for a class of systems having continuous relay nonlinearity. This continuous relay nonlinearity can be defined as an analytic nonlinear function having unknown parameters and bounded unmodeling part. By this mathematical modeling, the whole system can be considered as a nonlinear system having unknown parameters and bounded perturbation. The control algorithm of this paper, RALC, can be constructed by robust adaptive law, feedback linearization, and indirect robust adaptive control. By this RALC, we can obtain that the output of given system can follow that of a stable reference linear model made by designer and the boundedness of all signals in closed-loop system can be maintained. Therefore, we can confirm a robust adaptive control for a class of systems having continuous relay nonlinearity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.33.2-33
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• 2001

The robust stability condition for sampled-data control systems with a sector nonlinearity was presented in our previous paper. Although it is applicable only to the sampled-data control system of a certain class, a usual discretetime control system can belongs to this type of class. This paper analyzes the amplitude dependent behavior of nonlinear sampled-data (i.e., discrete-time) control systems in a frequency domain. By considering restricted areas (sectors) in the nonlinear characterisitic, the existence of a sustained oscillation is estimated, and the relationship between the stable/unstable conditions and the result derived from describing function is compared. Based on these considerations, the stabilization of nonlinear discrete-time control systems is examined in the frequency domain.

• International Journal of Control, Automation, and Systems
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• 제1권4호
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• pp.412-430
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• 2003

In many practical problems in signal processing and control, the signal values are often restricted to belong to a finite number of levels. These questions are generally referred to as "finite alphabet" problems. There are many applications of this class of problems including: on-off control, optimal audio quantization, design of finite impulse response filters having quantized coefficients, equalization of digital communication channels subject to intersymbol interference, and control over networked communication channels. This paper will explain how this diverse class of problems can be formulated as optimization problems having finite alphabet constraints. Methods for solving these problems will be described and it will be shown that a semi-closed form solution exists. Special cases of the result include well known practical algorithms such as optimal noise shaping quantizers in audio signal processing and decision feedback equalizers in digital communication. Associated stability questions will also be addressed and several real world applications will be presented.

• Journal of Periodontal and Implant Science
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• 제23권3호
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• pp.475-492
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• 1993

The effect of synthetic bone materials was assessed in the patients with pure periodontal class II and III furcation defects. The buccal aspects of the maxillary and mandilular first and second molars were surgically exposed, and synthetic bone materials were interposed between the gingival flap and the furcation defects in the experimental group. The control group were treated without the use of synthetic bone materials by same operator. Probing pocket depth, gingival recession, and loss of attachment, were measured by Michigan O-probe and tooth mobility was evaluated by an electronic mobility tester(Periotest(R), Siemens co. Germany) at preoperation and 3-, 6-, and 12-month postoperation. Standardized radiogrphs were taken at preoperation and 6-month and 12-month postoperation. The postoperative change of clinical parameters and the difference between experimental group and control group were statistically analyzed by Student, t-test. The results were as follows: 1. The probing pocket depth at the 3-, 6-, and 12-month postoperative examination was significantly decreased, compared to that at preoperative examination in both experimental group and control group(P<0.005), but there was no significantly difference between experimental group and control group. 2. The amount of gingival recession at the 3-, 6-, and 12-month postoperative examination was increased, compared to that at the preoperative examination in both experimental and control group(P<0.005). In the case of the class III furcation involvement, the amount of gingival recession at the 3-, 6-, and 12-month postoperative examination was more significantly increased in control group than experimental group(P<0.05). 3. The amount of loss of attachment at the 3-, 6-, and 12-month postoperative examination was significantly decreased, compared to that at the preoperative examination in both experimental and control group in the case of class II furcation involvement, and in experimental group only in the case of furcation III involvement(P<0.005). The amount of loss of attachment at, the 3-, 6-, and 12-month postoperative examination was more significantly decreased in experimental group than control group in the case of the class III furcation involvement(P<0.05), but in the case of class II furcation involvement there was no significant difference between experimental group and control group. 4. The tooth mobility at the 3-, 6-, and 12-month postoperative examination was significantly decreased, compared to that at the preoperative examination in both experimental and control group(P<0.005), but there was no significant difference between experimental group and control group. 5. Radiopacity of furcation area was greatly increased in the experiment group, but there was no radiographic change in the control group.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.87.1-87.1
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• 2011

The residential Fuel Cell system has high efficiency of 85% with transferring natural gas to electrical power and heat, directly and it is a friendly environmental new technology in that $CO_2$ emission can reduce 40% compared with conventional power generator and boiler. The residential fuel cell system consists of two main parts which have electrical and hot storage units. The electrical unit contains a fuel processor, a stack, an inverter, a control unit and balance of plant(BOP), and the cogeneration unit has heat exchanger, hot water tank, and auxiliaries. 5kW class fuel process was developed and tested from 2009, it was evaluated for long-term durability and reliability test including with improvement in optimal operation logic. Stack development was crried out through improvement of design and evaluation protocol. Development of system controller was successfully accomplished through strenuous efforts and original control logic was optimized in 5kW class PEMFC system. In addition, we have been focused on development of system process and assembly technology, which bring about excellent improvement of reliability of system. The 5kW class PEMFC system was operated under dynamic conditions for 1,000 hours and it showed a good performance of total efficiency and durability.

• Journal of Information Processing Systems
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• 제15권2호
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• pp.320-330
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• 2019

This study analyzed changes in sociality and democratic-citizenship among elementary school students in the information class and the science class at the Science Education Institute for the Gifted, who were divided into an experimental group and a control group. The experimental group engaged in the Learning Together (LT) cooperative form of learning for which the remix function of Scratch, an educational programming language, was applied, while the control group was given general instructor-led lessons. Members in the experimental group were able to modify processes during projects through the usage of the remix function, thereby actively participating in the projects and eventually generating team-based results. The post-class t-tests showed a greater degree of improvements in sociality and democratic citizenship for the experimental group that was offered the remix-function-based cooperative learning than the control group. Statistically significant differences were present between two groups particularly in "cooperative spirit" sub-domain of sociality and the "community" and "responsibility" sub-domains of democratic citizenship.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.146-154
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• 2006

In this paper, we propose direct and indirect adaptive fuzzy sliding mode control approaches for a class of nonaffine nonlinear systems. In the direct case, we use the implicit function theory to prove the existence of an ideal implicit feedback linearization controller, and hence approximate it to attain the desired performances. In the indirect case, we exploit the linear structure of a Takagi-Sugeno fuzzy system with constant conclusion to establish an affine-in-control model, and therefore design an indirect adaptive fuzzy controller. In both cases, the adaptation laws of the adjustable parameters are deduced from the stability analysis, in the sense of Lyapunov, to get a more accurate approximation level. In addition to their robustness, the design of the proposed approaches does not require the upper bounds of both external disturbances and approximation errors. To show the efficiency of the proposed controllers, a simulation example is presented.

• International Journal of Control, Automation, and Systems
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• 제5권5호
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• pp.492-500
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• 2007

This paper focuses on the problem of guaranteed cost control for a class of uncertain linear delay systems with actuator failures. When actuators suffer "serious failure" the never failed actuators can not stabilize the system, based on switching strategy of average dwell time method, under the condition that activation time ratio between the system without actuator failure and the system with actuator failures is not less than a specified constant, a sufficient condition for exponential stability and weighted guaranteed cost performance are developed in terms of linear matrix inequalities (LMIs). Finally, as an example, a river pollution control problem illustrates the effectiveness of the proposed approach.

• International Journal of Control, Automation, and Systems
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• 제5권2호
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• pp.138-146
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• 2007

The analysis and design method for achieving robust stabilization of Decentralized Dynamic Surface Control (DDSC) is presented for a class of interconnected nonlinear systems. While a centralized design approach of DSC was developed in [1], the decentralized approach to deal with large-scale interconnected systems is proposed under the assumption that interconnected functions among subsystems are unknown but bounded. To provide a closed-loop form with provable stability properties, augmented error dynamics for N nonlinear subsystems with DDSC are derived. Then, the reachable set for errors of the closed-loop systems will be approximated numerically in the form of an ellipsoid in the framework of convex optimization. Finally, a numerical algorithm to calculate the $L_2$ gain of the augmented error dynamics is presented.

• 한국군사과학기술학회지
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• 제16권6호
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• pp.752-761
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• 2013

A new gun fire control system has been developed for the Korean next generation frigate class. The engineering requirement was far more tightened than the PKG-A class for the firing range availability and gun control function since 5 inch gun is adopted for the new ship. We mention about the principal technologies required to build a generic gun fire control system and proposed methods for the new gun fire control system. The new system has been designed based on the proposed methods in order to satisfy the requirement and functionality has been proved to be acceptable through the sea trial by Korean navy.