• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1899-1903
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• 1991

This paper presents a water level control method using Z-80 microcomputer. The process considered in this paper is one tank system which is described by an unknown nonlinear differential equation. The water level is measured by the end of bar installed at a float passing through 8 pair of photointerrupters located at equal distance. Therefore, the input data to 8255 which is interface between Z-80 and photointerrupters is discrete value, namely, value under 1. values from 1 to 8, and value upper 8. The water is pumped into the tank from a reservoir by switching on a relay connected to a moter and pump driving system. The pumping is stopped by switching off the relay. Experimental studies for two types of controllers are performed in order to investigate the control performance of water level of the water pumping system.

• Journal of the Korean Society for Nondestructive Testing
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• 제23권6호
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• pp.622-634
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• 2003

This paper is concerned with a computational method for recovering a crack shape of steam generator tubes of nuclear plants. Problems on the shape identification are discussed arising in the characterization of a structural defect in a conductor using data of eddy current inspection. A surface defect on the generator tube ran be detected as a probe impedance trajectory by scanning a pancake type coil. First, a mathematical model of the inspection process is derived from the Maxwell's equation. Second, the input and output relation is given by the approximate model by virtue of the hybrid use of the finite element and boundary element method. In that model, the crack shape is characterized by the unknown coefficients of the B-spline function which approximates the crack shape geometry. Finally, a parameter estimation technique is proposed for recovering the crack shape using data from the probe coil. The computational experiments were successfully tested with the laboratory data.

• Proceedings of the KIEE Conference
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.341-344
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• 1991

Rules in expert system have meaning of assigning never-happen-minterms. Overall logical relations of variables can be achived by making all prime implicants of never-happen-minterms. From prime implicants, two tables, which are necessary in the process of inference, are constructed. There are two inferencing modes. One excutes inference only one variable which the user is interested in, and the other excutes inference all variables simultaneously. Outputs of inference have not only 'true' or 'false' but also 'unknown' which is different from conventional expert system. In this paper, an efficient approach is presented, which can check logical inconsistency in knowledge base and contradiction between input facts and rules. The methods in the paper may be available in the field of diagnosis and alarm processing.

• Journal of Institute of Control, Robotics and Systems
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• 제7권8호
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• pp.647-655
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• 2001

In adaptive neuro-control, neural networks are used to approximate unknown plant nonlinearities. Until now, most of the studies in the field of controller design for nonlinear system using neural network considers the affine system with fixed number of neurons. This paper considers nonaffine nonlinear systems and on-line variation of the number of neurons. A control law and adaptive laws for neural network weights are established so that the whole system is stable in the sense of Lyapunov. In addition, at the expense of th input, tracking error converges to the arbitrary small neighborhood of the origin. The efficiency of the proposed scheme is shown through simulations ofa simple nonaffine nonlinear system.

• Proceedings of the KIEE Conference
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.389-391
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• 1994

This paper proposes an approach to control the current amplitude and phase simultaneously. To do this, variable structure control and adaptive parameter estimation arc applied to the current control of a single-phase PWM inverter with unknown R-L series load. The load parameters, R and L, are estimated by using the recursive least square method and these parameters are used to adjust the feedback gains of control input. The inverter system is modelled in a 2nd-order system by treating load current variation caused by inductive component as a disturbance. Simulation and experiment based on the 2nd -order model are done and the results show good dynamic response and low THD.

• Journal of information and communication convergence engineering
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• 제6권4호
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• pp.359-363
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• 2008

In this paper, the capacity of MIMO fading channel in the OFDM-based spatial multiplexing systems is analyzed when there is scattering at both transmitter and receiver. The employed MIMO channel model is spanning from the correlated low-rank case to uncorrelated high-rank case at both transmitter and receiver. The effects of spatial fading correlation on the capacity of MIMO channel is examined when the channel is known and unknown at the transmitter. We also evaluate the impacts of a channel estimation error at the transmitter on the MIMO channel capacity.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• 제6권4호
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• pp.238-242
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• 2013

We consider the problem of constructing observers for nonlinear systems with unknown inputs. Connectionist networks, also called neural networks, have been broadly applied to solve many different problems since McCulloch and Pitts had shown mathematically their information processing ability in 1943. In this thesis, we present a genetic neuro-control scheme for nonlinear systems. Our method is different from those using supervised learning algorithms, such as the backpropagation (BP) algorithm, that needs training information in each step. The contributions of this thesis are the new approach to constructing neural network architecture and its training.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제27권7호
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• pp.95-100
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• 2013

In this paper, we propose an active controller for high-speed pantograph in order to improve the transient response. Electrical power is delivered from a catenary to the train via a pantograph and thus it is very important to regulate the contact force between catenary and pantograph. By regarding the catenary displacement as an unknown disturbance input and analyzing the frequency response from the disturbance to contract force. we present an active controller that utilizes the lead compensator and resonant controller. It is shown by the computer simulation that the substantial improvement in transient response can be achieved by the proposed controller.

• 연구논문집
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• 통권34호
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• pp.87-99
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• 2004

A spring tension control device is used as a very important part of an twister system. The friction force of tensioner must keep same friction force during winding in package. For satisfy this function, many device used common compression coil spring. In this paper, by using the case-building technique which was based on simple theory that unknown design variables are induced by given input design variables by the designer, design automation algorithm about rectangular section compression springs with elastic characteristic is developed. Four design equation are justified in using of analysis of torsion of straight bar of rectangular section and geometrical condition of coil spring. Four design equation and nine design variables are computed by case-building technique.

• The Transactions of the Korean Institute of Electrical Engineers
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• 제39권4호
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• pp.364-370
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• 1990

In this paper, we propose a self-tuning PID controller for unknown systems with time-varying delay. Using pole placement equations, we derive the controller that can be extended to the multi-step time delay case. The time-varying delays are estimated by a prediction error delay method using multiple predictors. Since the order of the estimation vector is not increased, the persistant exciting condition of control input is alleviated. Since the least square method gives biased parameter estimates for colored noise cases, the recursive instrumental variable method is used to estimate system parameters. The computational burden of the proposed method is less than the conventional adaptive methods. Computer simulations are performed to illustrate the efficiency of the proposed method.