• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.620-623
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• 1996

POSCO has been developed a general purpose dynamic simulator of the hot strip steel mill. The simulator is a tool for developing the process control system in an industrial system solution business, by making the most use of control and simulation techniques fostered in steelmaking business. This simulator has, not only a powerful numerical analysis function, but an easy-to-use graphic user interface which readily enables to simulate dynamic system. This paper presents the features of the simulator and steel rolling process simulator as its application.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.350-355
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• 1990

A pressure tracking of hydroforming process is considered in this paper. To account for nonlinearities and uncertainty of the process. A fuzzy SOC based iterative learning control algorithm is proposed. A series of experimentals were performed for the pressure tracking control of the process. The experimental results show that regardless of inherent nonlinearties and uncertainties associated with hydraulic system. A good pressure tracking control performance is obtained using the proposed fuzzy learning control algorithm.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.492-498
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• 2022

Process control systems used in most domestic petrochemical corporates today are based on the Windows platforms. As technology leans toward opened environment, the exposure risk of control systems is increasing. However, not many companies are preparing for various cyberattacks due to lack of awareness and misunderstanding of cyber intrusion. This study investigated the extent of how much exposed the petrochemical process control system is to security threats and suggested practical measures to reduce OT cybersecurity vulnerabilities. To identify the cyber threat status of process control systems, vulnerabilities of the Windows platform, a principal cyber threat factor, have been analyzed. For research, three major DCS providers in Korea and the discontinuation of Windows platform of 635 control systems were investigated. It was confirmed that 78% of the survey subjects were still operating in the discontinued windows platforms, and those process control systems were operated in a state vulnerable to cyber intrusions. In order to actively cope with these cyber threats, legal regulations such as designation of critical infrastructure for major petrochemical facilities which is implemented in advanced countries such as the United States are needed. Additionally, it is necessary to take the initiative in eradicating security threats to the process control systems by aggressively introducing security solutions provided from existing DCS suppliers. This paper was submitted to Professor Ko JaeWook's retirement anniversary issue.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.219-222
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• 1997

Due to the unpredictability and irregularity, the behaviors of chaotic systems are considered as undesirable phenomena to be avoided or controlled. Thus in this paper, to control systems showing chaotic behaviors, a direct adaptive control method using a radial basis function network (RBFN) as an excellent alternative of multi-layered feed-forward networks is presented. Compared with an indirect scheme, a direct one does not need the estimation of the controlled process and gives fast control effects. Through simulations on the two representative continuous-time chaotic systems, Duffing and Lorenz systems, validity of the proposed control scheme is shown.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.329-337
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• 2000

This study describes a pressure tracking control of hydroforming process which is used for precision forming of sheet metals. The hydroforming operation is performed in the high-pressure chamber strictly controlled by pressure control valve and by the upward motion of a punch moving at a constant speed, The pressure tracking control is very difficult to design and often does not guarantee satisfactory performances be-cause of the punch motion and the nonlinearities and uncertainties of the hydraulic components. To account for these nonlinearities and uncertainties of the process and iterative learning controller is proposed using Cerebellar Model Arithmetic Computer (CMAC). The experimental results show that the proposed learning control is superior to any fixed gain controller in the sense that it enables the system to do the same work more effectively as the number of operation increases. In addition reardless of the uncertainties and nonlinearities of the form-ing process dynamics it can be effectively applied with little a priori knowledge abuot the process.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.1062-1070
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• 2009

The strip shape for the stainless steel process has made an issue of the strip quality, and hence the shape control method is developed at the Sendzimir rolling mill (ZRM). ZRM is a stainless cold rolling mill and has actuators for the shape control. They are first intermediate rolls and top crown rolls, which are controlled horizontally and vertically, respectively. The shape control of the stainless steel rolling process has difficulty in obtaining the symmetrical shape. The objective of the shape control is to minimize the shape deviation and to maintain stable state, which keeps symmetrical shape pattern in the lateral direction. The method of the shape recognition employs a least squares method and neural network. The shape deviation is the difference between the target shape and actual shape and is controlled by the fuzzy shape control. The fuzzy shape control using operator's informative knowledge is proposed in this paper. The experiments are carried out online for various stainless materials and sizes. The productivity of the rolling process has increased from 9.0 to 9.4 tons per hour.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.7
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• pp.557-561
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• 2016

Recently, in the manufacturing process of flat panel displays, mass production methods of inline system has been emerged. In particular the next generation OLED display manufacturing process, horizontal inline evaporation process has been tried. It is important for the success of OLED inline evaporation process to develop a magnetic levitation transport system capable of transferring a carrier equipped with a mother glass with high accuracy without any physical contact along the rail under vacuum condition. In the case of existing wheel-based transfer system, it is not suitable for OLED evaporation process requiring high cleanliness. On the other hand, the magnetic levitation transport system has an advantage that it does not generate any dust and it is possible to achieve high-precision control because there are not non-linear factors such as friction force. In this paper, we introduce the high-precision magnetic levitation transport system, which is currently under development, for OLED evaporation process.

• Journal of Information Technology Services
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• v.10 no.2
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• pp.141-162
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• 2011

The controls of Information Systems (IS) have been an more critical issue controls as the sophistication and integration of IS is more proceeded. ITGI (The Information Technology Governance Institute) of ISACA (Information Systems Audit and Control Association) has suggested COBIT (Control Objectives for Information and related Technology) and this has been widely recognized the evaluation model of IS controls. In COBIT, IS was evaluated in terms of process, information quality, and IT resources. This study used COBIT in order to suggest and empirically test an evaluation model of IS service. The data was collated from one major Chinese SI (Systems Integration) company in four domains of processes : planning and organization, acquisition and implementation, delivery and support, and monitoring. Seven factors are extracted using an exploratory factor analysis as follows : Overall IT planning process, technological assessment process in IT planning of IT, cost-benefit assessment process in IT planning, implementation process, support process, monitoring process, post-implementation evaluation process. The results of confirmatory analysis of three alternative measurement models indicated that the measurement model with one inherent or conceptual variable has greater model fitness than the other models. This study suggests the logical and general way to test and apply COBIT in evaluating IS services.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.954-959
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• 2008

This paper is concerned with the reliable $H_{\infty}$ controller design problem for uncertain linear systems against actuator failures. In the design, the $H_{\infty}$ performance of the closed-loop system is optimized during normal operation(without failures) while the system satisfies a prescribed $H_{\infty}$ performance level in the case of actuator failures. Single and parameter-dependent Lyapunov function approaches are applied in designing suboptimal reliable $H_{\infty}$ controllers. Simulation studies are presented to demonstrate the effectiveness of the proposed design procedures.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.10
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• pp.1006-1012
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• 2010

The hot rolling process ranks the highest position for production in steel making process. The hot strip manufacturing processes consist of the reheating furnace, roughing and finishing mill and coiler. The reheating furnace heats the slab. The roughing and finishing mill produce the hot strip from slab. The hot strip quality mainly depends on finishing mill, which consists of 4-high 7 stands. The looper is installed between stands and is used for controlling the strip tension by the looper angle for better material flow. It is difficult to control the strip tension with the coupled looper system from interaction between the looper angle and strip tension. Too much deviation of strip tension severely affects the poor width quality of the hot strip. It is important to control simultaneously both the looper angle and strip tension with each of their target values. This paper proposes the fuzzy tension control, which is developed to minimize the width deviation of the hot strip by maintaining the proper strip tension between stands and to achieve the stable operation of the coupled looper system. The fuzzy tension control performance is compared with the conventional PID control by experimental results.