• Proceedings of the Technology Innovation Conference
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• 2000.06a
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• pp.47-64
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• 2000

This paper analyses characteristics of the numerical controller industry in market formation and the Flow of information between users and producers and the characteristic of knowledge base of the industry and discusses the difficulties derived, from the characteristics, in accumulation of technological capability In market formation betweenusers and producers, the multi-layered market is not favorable to domestic producers in that lower end market is not large enough to provide cardle market to them which produce inferior quality and lower price than importer products. The credibility of the permance of a product is difficult to prove until a critical mass of products are sold. Therefore gaining market share is deterred by unproven credibility of the performance of the product. The flow of information between users and producers is limited. The flow of information on users environment through mass market to producers is essential for improving credibility of a product. The nature of knowledge base is tacit and the means of knowledge transmission is limited. Technological licensing and reverse engineering, Which have been conventional industry. These characteristics provide conditions of vicious circle in accumulation of technological capability of the numerical controller industry. This paper argues that these characteristics of the industry challenges existing approach to R&D management and framework of science and technology policy.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.1
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• pp.19-25
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• 2007

The MFC(Mass Flow Controller) is an equipment that measures and controls mass flow rates of fluid. Most of the HFC system is still using the PID algorithm. The PID algorithm shows superior performance on the MFC system. But the PID algorithm in the MFC system has a few problems as followed. The characteristic of the MFC system is changed according to the operating environment. And, when the piezo valve that uses the control valve is assembled in the MFC system, a coupling error is generated. Therefore, it is very difficult to find out the exact parameters of MFC system. In this paper, we propose adaptive PID algorithm in order to compensate these problems of a traditional PID algorithm. The adaptive PID algorithm estimates the parameters of MFC system using LMS(Least Mean Square) algorithm and calculates the coefficients of PID controller. Besides, adaptive PID algorithm shows better transient response because adaptive PID algorithm includes a feedforward. And we implement MFC system using proposed adaptive PID algorithm with self-tuning and Ziegler and Nickels's method. Finally, comparative analysis of the proposed adaptive PID and the traditional PID is shown.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.40-47
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• 2005

The objective of this paper is to analyze power system dynamics influenced by UPFC(Unified Power flow Controller) operation and to develop a refined DCRM(Differential Current Relaying Method) to protect the transmission line with UPFC effectively. The implementation of control strategies for UPFC introduces new power system dynamic problems that must be considered while applying the conventional DCRM. In this paper, impact of UPFC operation on the DCRM has been reviewed and a refined DCRM has been proposed to detect faults properly in spite of UPFC operation. The porposed method is verified by simulation on the line-faulted system with UPFC.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.847-848
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• 2008

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.647-651
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• 1987

Yeast biomass in a biological continuous stirred tank reactor was controlled with an APPLE II microcomputer using adaptive control theory of bilinear systems. The controller used is as simple as a PID controller, but required less information. Cell concentration was well controlled by adjusting the inlet flow rate following the algorithm.

• Journal of Electrical Engineering and Technology
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• v.11 no.5
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• pp.1057-1062
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• 2016

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.3
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• pp.95-106
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• 2000

The load frequency control of power system is one of important subjects in view of system operation and control. That is even though the rapid load disturbances were applied to the given power system, the stable and reliable power should be supplied to the users, converging unconditionally and rapidly the frequency deviations and the tie-line power flow one on each area into allowable boundary limits. Nonetheless of such needs, if the internal parameter perturbation and the sudden load variation were given, the unstable phenomenal of power system can be often brought out because of the large frequency deviation and the unsuppressible power line one. Therefore, it is desirable to design the robust neuro-fuzzy controller which can stabilize effectively the given power system as soon as possible. In this paper the robust neuro-fuzzy controller was proposed and applied to control of load frequency over multi-area power system. The architecture and algorithm of a designed NFC(Neuro-Fuzzy Controller) were consist of fuzzy controller and neural network for auto tuning of fuzzy controller. The adaptively learned antecedent and consequent parameters of membership functions in fuzzy controller were acquired from the steepest gradient method for error-back propagation algorithm. The performances of the resultant NFC, that is, the steady-state deviations of frequency and tie-line power flow and the related dynamics, were investigated and analyzed in detail by being applied to the load frequency control of multi-area power system, when the perturbations of predetermined internal parameters. Through the simulation results tried variously in this paper for disturbances of internal parameters and external stepwise load stepwise load changes, the superiorities of the proposed NFC in robustness and adaptive rapidity to the conventional controllers were proved.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.3
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• pp.363-369
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• 1999

In this paper, we design the robust $H_{\infty}$ controller for water level control of steam generator using a mixed $H_{\infty}$ optimization with model-matching method. Firstly we choose the desired model which has good disturbance rejection performance. Secondly we design a stabilizing controller to keep the model-matching error small and also provide sufficiently large stability margin against additive perturbations of the nominal plant. Simulation results show that proposed robust $H_{\infty}$ controller at specific power operation has satisfactory performances against the variations of load power, steam flow rate, primary circuit coolant temperature, and feedwater temperature. It can be also observed that the proposed robust $H_{\infty}$ controller exhibits better robust stability than conventional PI controller.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.404-408
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• 2013

In this Study, another way to accomplish the goal of meeting large steam-flow requirements is the use of multiple valves. Multiple valves can provide better control in meeting the precision pressure controller requirements. Simulation demonstrates the effectiveness of the pressure controller. The key point of this study is to precisely control the position of the control valve on the outside of the electro-hydraulic system using a special PID controller. Simulation and experiments verify the performance of the controller.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.149-152
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• 2002

The aim of this study is to analyse the problems occurred by using classical algorithm to synthesize the H$\infty$ optimal controller. The obtained result of analysis applied to the composition of algorithm for the new H$\infty$ optimal controller which was introduced in this study. The study investigates and compares H$\infty$ optimal controller formed by new algorithm with the one formed by classical algorithm. In particular, robustness related to the robust control is systematically described by using the composition of algorithm for the classical H$\infty$ optimal controller. In addition, the flow charts classified into classical algorithm and new one are discussed to synthesize the H$\infty$ optimal controller.