• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.157-166
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• 2005

This article involves architecting prototype-fuzzy expert system for designing the nominal cover thickness by means of fuzzy inference for quantitatively representing the environment affecting factor to reinforced concrete in chloride-induced corrosion environment. In this work, nominal cover thickness to reinforcement in concrete was determined by the sum of minimum cover thickness and tolerance to that defined from skill level, constructability and the significance of member. Several variables defining the quality of concrete and environment affecting factor (EAF) including relative humidity, temperature, cyclic wet and dry, and the distance from coast were treated as fuzzy variables. To qualify EAF the environment conditions of cycle degree of wet-dry, relative humidity, distance from coast and temperature were used as input variables. To determine the nominal cover thickness a qualified EAF, concrete grade, and water-cement ratio were used. The membership functions of each fuzzy variable were generated from the engineering knowledge and intuition based on some references as well as some international codes of practice.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.1
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• pp.34-39
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• 2015

In this paper, a finite impulse response (FIR) filter is proposed for discrete-time nonlinear systems. The proposed filter is designed by combining the estimate of the perturbation state and nominal state. The perturbation state is estimated by adapting the optimal time-varying FIR filter for the linearized perturbation model and the nominal state is directly obtained from the nonlinear nominal trajectory model. Since the FIR structured estimators use the finite horizon information on the most recent time interval, the proposed extended FIR filter satisfies the bounded input/bounded output (BIBO) stability, which can't be obtained from infinite impulse response (IIR) estimators. Thus, it can be expected that the proposed extended FIR filter is more robust than IIR structured estimators such as an extended Kalman filter for the round-of errors and the uncertainties from unknown initial states and uncertain system model parameters. The simulation results show that the proposed filter has better performance than the extended Kalman filter (EKF) in both robustness and fast convergency.

• Journal of Power System Engineering
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• v.17 no.3
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• pp.82-88
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• 2013

For commercialized servo drives of the motion stage to include embedded controller, external terminal is provided for tracking command and encoder output, but internal terminal is not for control input. Thus, it is difficult to combine out signal of embedded controller with that of external compensator such as disturbance observer. In this study, for precise tracking control of motion stage without hardware change of the servo drive, tacking control system is composed of an inner loop of servo drive and an outer loop of disturbance observer. Then, the control system is designed so that the output response of actual plant corresponds with nominal model's in transient state as well as in steady state. Finally, the experiment results show that the designed control system is effective to reconcile actual plant behavior with nominal model under nonlinear friction and parameter perturbation.

• Structural Engineering and Mechanics
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• v.26 no.4
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• pp.377-392
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• 2007

A discrete sliding mode control (SMC) method based on hybrid model of neural network and nominal model is proposed to reduce the vibration of flexible structures, which is a robust active controller developed by using a sliding manifold approach. Since the thick boundary layer will reduce the virtue of SMC, the multilayer feed-forward neural network is adopted to model the uncertainty part. The neural network is trained by Levenberg-Marquardt backpropagation. The design objective of the sliding mode surface is based on the quadratic optimal cost function. In course of running, the input signal of SMC come from the hybrid model of the nominal model and the neural network. The simulation shows that the proposed control scheme is very effective for large uncertainty systems.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.591-601
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• 2006

In this paper, we present a new control methodology for perturbed crane systems. Nonlinear crane systems are transformed to linear models by feedback linearization. An inverse dynamic equation is applied to compute the system PD control force. The PD control parameters are selected based on a nominal model and are therefore suboptimal for a perturbed system. To achieve the desired performance despite model perturbations, we construct a neural network auxiliary controller to compensate for modeling errors and disturbances. The overall control input is the sum of the nominal PD control and the neural auxiliary control. The neural network is iteratively trained with a perturbed system until acceptable performance is attained. We apply the proposed control scheme to 2- and 3-degree-of-freedom (D.O.F.) crane systems, with known bounds on the payload mass. The effectiveness of the control approach is numerically demonstrated through computer simulation experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1203-1211
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• 2017

This paper proposes a robust controller for flexible joint robots to achieve tracking performance and to improve robustness against both matched and mismatched disturbances. The proposed controller consists of a disturbance observer(DOB), passivity-based controller, and integral sliding mode controller(ISMC) in a backstepping manner. The DOB compensates the mismatched disturbance in the link-side and formulates the reference input for the motor-side controller. Interconnection and damping assignment passivity-based controller (IDA-PBC) performs tracking control of motor-side, and it is integrated to nominal control of ISMC to guarantee the over-all stability of the nominal system, while, matched disturbances are decoupled by the discontinuous control of ISMC. In the design of the link-side controller, PD type impedance controller is designed with DOB and this leads the continuous control input which is suitable to the reference input for the motor-side.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2143-2146
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• 2003

We propose, for the first time to our knowledge, a novel gain-clamping method for EDFA in WDM Add/Drop networks by introducing a disturbance observer technique. The proposed gain-clamping control input consists of the nominal gain-clamping control such as PI(Proportional and Integral) control and the additional control input for the compensation of the effects caused by channel add/drops. The additional control input is designed using the wellknown disturbance observer technique and can be implemented very easily with general electric elements. We proved the superiority of the new technique over the previous methods by showing simulation result of minimized dips and spikes that appear in power profile of EDFA output.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.228-230
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• 2008

A LLC resonant converter with hold-up time extension technique for computer power supply is proposed. Since the proposed circuit has a current boost-up capability of resonant inductor regardless of the input voltage level and the load power condition, operating near the resonant frequency, it can provide the power to the load as the input voltage drops to half of reflected output voltage to the transformer primary. This extends the hold-up time of computer power supply and improves the system power density and conversion efficiency at nominal input voltage. The experimental results with prototype are given to confirm the validity of the proposed circuit.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1008-1009
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• 2015

An emergency diesel generator system is an independent source of power that supports important electrical systems on loss of normal power supply. AVR(Automatic Voltage Regulator) is a regulator which regulates the output voltage at a nominal constant voltage level. Specially, a power supply for the AVR must be operated at the very wide input range. In this paper, a flyback power supply with very wide input voltage range is proposed.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.9
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• pp.745-751
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• 2000

In this paper, the novel sliding durfaces are proposed by defining the virtual states. These sliding surfaces have the nominal dynamics of the original system and make it possible that the sliding Mode Control(SMC) technique is used with various types of controllers. Its design is based on the augmented system which additional dynamics as many as input numbers. The reaching phase is eliminated by using the initial virtual states which make the initial sliding functions equal to zero.