• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.286-290
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• 2000

Optimal neuro-control algorithm is extended to the control of a multi-degree-of-freedom structure. An active mass driver(AMD) system on the top roof is used as an exciter. The control signals are made by a multi-layer perceptron(MLP) which is trained by minimizing a sub-optimal performance index. The performance index is a function of both the output responses and the control signals. Structure having nonlinear hysteretic behavior is also trained and controlled by using proposed control algorithm. In training neuro-controller, emulator neural network is not used. Instead, sensitivity-test data are used. Therefore, only one neural network is used for the control system. Both the time delay effect and the dynamics of hydraulic actuator are included in the simulation. Example shows that optimal neuro-control algorithm can be applicable to the multi-degree of freedom structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.731-736
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• 2003

Alkali silicate system has wide application to accelerating admixture for shotcrete, but it has several problems that decrease long-term strength and delay setting time. So alkali-free system was gradually focused on accelerating admixtures for shotcrete due to its environmental property. The aim of this study is to investigate effect of alkali-free accelerating admixtures on aluminum sulfate system containing diethanolamine or acrylic acid etc. The alkali-free accelerating admixture has better properties than silicate system accelerating admixtures on compressive strength and low pH as shotcrete. Especially, the compressive strength of alkali-free accelerating admixture containing diethanolamine was increased about 10% compared with the value of ordinary portland cement.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.321-323
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• 2006

The IEEE 802.15.4 uses a CSMA/CA algorithm on access of media. The CSMA/CA algorithm does Random Backoff before the data is transmitted to avoid collisions. The random backoff is a kind of unavoidable delays and introduces the side effect of energy consumptions. To cope with those problems we propose a new media access algorithm, the Priority Based Ordered Media Access (PBOMA) algorithm, which uses different IFSs. The PBOMA algorithm uses Sampling Rate and Beacon Interval to get a different access probability(or IFS). The access probability is higher, the IFS is shorter. Note that The transfer of urgent data uses tone signal to transmit it immediately. The proposed algorithm is expected to reduce the energy consumptions and the delay.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2098-2102
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• 2007

The conventional CCPU(Cable Covering Protective Unit) modeling methods which are used by Type 99 and Type 92 in EMTP simulation are firstly discussed in this paper, and then some problems of them are also investigated. Modeling method using Type 99 causes unstable characteristic at initial transient of CCPU operation. Time delay has also effect on the output of CCPU modeling. So, in this paper, a new modeling method for CCPU is designed by DBM(Data Base Module) of EMTP. The characteristic of Type 92 is used for the new modeling method. The reliability of this one is proved by comparing simulation with measured data. Specially, at initial transient, the waveform of the new method shows more stable result than that of conventional method using Type 99. Also, the peak value is similar to measured data.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1687-1688
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• 2008

The steam superheater and the steam pressure systems are time delay systems that have poles near the origin in the left half plane or a pure integrator. Smith predictor can't be applied to these systems any more, because of occurring the steady state error for the step disturbance. In this paper, a new Smith predictor controller for the steam superheater and the steam pressure is proposed. A disturbance observer to estimate an input disturbance and a new controller to eliminate an effect of a disturbance are proposed. The computer simulation results are shown the efficiency of the proposed system.

• Journal of ILASS-Korea
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• v.14 no.3
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• pp.117-121
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• 2009

Biodiesel fuel has different spray patterns, because viscosity and surface tension of biodiesel fuel are higher than that of diesel fuel. The diesel combustion is strongly controlled by the fuel spray behavior in combustion chamber. So, it was needed to understand the spay characteristics of non-esterification biodiesel fuel. In this study, the spray characteristics of non-esterification biodiesel fuel was investigated to confirm of an effect of WDP. The characteristics of fuel atomization was analyzed with SMD and span factor through laser diffraction particle analyzer (LDPA), and the process of spray injection was visualized through the visualization system composed of a halogen lamp and high speed camera. It was found that injection delay time and SMD of blended fuel with WDP get shoter and smaller than that of non-esterification biodiesel fuel.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.136-136
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• 2000

The direct drive servo valve(DDV) is composed of a DC rotor, link, valve spool and displacement sensor(LVDT) where the spool is directly coupled to the DC motor through the link. Since the DDV is a kind of one-stage valve, the robust controller is required to overcome the flow force effect on the spool motion. The mathematical equations are derived and the stability, accuracy and response speed of a DDV are investigated analytically using a linearized system block diagram. Proportional control, PID control. Time-Delay control, Sliding Mode control, and Proportional control using the load pressure are applied to DDV to find which one shows the best control performance. The digital computer simulation results show that the proportional control using the load pressure satisfies the design requirement of response speed and steady state error regardless of the variation of load pressure,

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.248-254
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• 1996

A disturbance rejection controller using eccentricity filtering and LQ control techniques is proposed to alleviate significantly the effect of roll eccentricity in multivariable cold-rolling processes. Fundamental problems such as process time delay inherent in exit thickness measurement and non-stationary characteristics of roll eccentricity signals can be overcome by the proposed control method. The filtered instantaneous estimate of roll eccentricity may be exploited to improve instantaneous estimate of the exit thickness variation based on roll force and roll gap mearsurements, and a feedforward compensator is augmented as a reference for a gaugemeter thickness estimator. And, LQ feedback controller is combined with eccentricity filter for the attenuation of the exit thickness variation due to the entry thickness variation. The simulation results show that eccentricity components have been significantly eliminated and simultaneously other distrubances also have been attenuated.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.7-10
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• 1990

In this paper the instability analysis of Inverter fed Induction motor drive system is performed by calculate the eigen value of the linearised equation which describe the behavior of the Induction motor. Inverter fed Induction motor drive system may become unstable at low speeds(frequencies) even though balanced, sinusoidal voltage are applied. Effect for the change of machine parameter and Inverter delay time are simulated by digital computer.

• Journal of ILASS-Korea
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• v.20 no.4
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• pp.241-246
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• 2015

The objective of the current study is to develop an 1D thermoacoustic model for predicting basic characteristics of combustion instability and to investigate effects of key parameters on the instabilities such as effects of flame geometry and acoustic boundary conditions. Another focus of the paper is placed on limit cycle prediction. In order to improve the model accuracy, the 1D model was modified considering the actual flame location and flame length (i.e. distribution of time delay). As a result, it is found that the reflection coefficients have a great effect on the growth rate of the instabilities. In addition, instability characteristics are shown to be strongly dependent upon the fuel compositions.