• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.826-829
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• 1993

Existing fuzzy control methods do not perform well when applied to systems containing nonlinearities arising from unknown deadzones. We propose a novel two-layered fuzzy logic controller for controlling systems with deadzones. The two-layered control structure consists of a fuzzy logic-based pre-compensator followed by a conventional fuzzy logic controller. Our proposed controller exhibits superior transient and steady-state performance compared to conventional fuzzy controllers. We illustrate the effectiveness of our scheme using computer simulation examples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.3
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• pp.213-220
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• 1990

DC servo motor has been often used as the position control system, because the performance is excellent on the velocity and position control system. When the unknow disturbance and accessible load torque are imposed on the position control of DC servo motor, this system has the steady and/or transient state error. In this paper, a new method which has high stiffness for reducing the error is proposed. This error will be reduced by acceleration control. The effectiveness of the acceleration control is confirmed by using computer simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2139-2146
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• 2011

In this paper, a robust adaptive controller is proposed for trajectory tracking of robot manipulators with the unknown friction coefficient and bounded disturbance. A new adaptive control law is developed based on sliding mode and derived from the Lyapunov stability analysis. The introduction of a boundary layer solves the problem of chattering. The proposed adaptive controller is globally asymptotically stable and guarantees zero steady state error for joint positions. The estimated friction coefficients can also approach the actual coefficients asymptotically. A simulation example is provided to demonstrate the performance of the proposed algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.944-949
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• 2009

A simplified power control technique for electronic ballasts of HID lamps is proposed. This power calculator and controller consist of regular operational amplifiers with some passive elements and form simple add operation circuit. From a mathematical model of designed ballast with proposed power controller, the control performance and stability are analyzed by using Matlab and the results show that the stable starting characteristics and steady state characteristics of HID lamp are appropriately guaranteed. The experimental results of the prototype ballast coincide with the simulation results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2028-2037
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• 2009

This paper presents the simulator for dynamic modeling of a MT(micro turbine) during start-up period. The simulator is implemented by modeling a dynamic power of main components of a MT including compressor, combustor and turbine. A modeling for a MT under steady state operation can be accurately built from thermodynamics analysis. But dynamic modeling during start-up period is very difficult because efficiency of main components is very low and the designed value has big error and nonlinear characteristics during start-up. In this paper, new method without using thermodynamics analysis during start-up is proposed for the simulator. The power models of main components are derived from analysis of the experimental operation data by test motoring using a electric starter under constant power output. The simulator is developed using MATLAB/Simulink. For constant power output control, sensorless vector inverter is designed and algorithms for starting from stall and method for controling a output power are proposed. The performance of developed simulator is verified by comparing experimental and simulation start-up results.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1182-1187
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• 2014

This paper proposes an energy management strategy and adaptive control for superconducting magnetic energy storage (SMES) in a distribution power system with a grid-connected photovoltaic (PV) farm. Application of the SMES system can decrease the output power fluctuations of PV system effectively. Also, it can control the real and reactive powers corresponding to the scheduled reference values with adequate converter capacity, which are required at a steady-state operating point. Therefore, the adaptive control strategy for SMES plays a key role in improving the system stability when the PV generation causes uncertain variations due to weather conditions. The performance of proposed energy management strategy and control method for the SMES is then evaluated with several case studies based on the PSCAD/EMTDC$^{(R)}$ simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1730-1734
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• 2005

In this paper, a new Smith predictor controller for a disturbance adding to input side of a time delay plant is proposed. A disturbance observer is obtained to estimate an input disturbance and the new Smith predictor controller to eliminate the effects of a disturbance is designed using the disturbance observer. As a result, the proposed Smith predictor controller can make a steady state error for step input disturbance zero quickly. The effectiveness and the improved performance of the proposed system are verified by computer simulation.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.4
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• pp.214-218
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• 2002

In this paper, the effectiveness of three different control algorithms are thoroughly investigated via simulation and a proposed efficiency evaluation method of experimentation. Both the steady state and transient characteristics of each control algorithm along with its measured efficiency are analyzed. Finally, a novel two-mode maximum power point tracking (MPPT) control algorithm combining the constant voltage control and the incremental conduction (IncCond) methods is proposed to improve the efficiency of the 3KW PV power generation system at different insolation conditions. Experimental results show that the proposed two-mode MPPT control provides excellent performance at less than 30% insolation intensity, covering the whole insolation area without additional hardware circuitry.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.1
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• pp.29-36
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• 2020

In this study, a variable step algorithm is proposed on the basis of the perturb and observe method. The proposed algorithm can follow the maximum power point (MPP) quickly when solar irradiance changes rapidly. The proposed technique uses the voltage change characteristic at the MPP when the environment changes because of insolation or temperature. The MPP is tracked through the voltage control using a variable step method. This method determines the sudden change of solar irradiance by setting the threshold value and operates in fast tracking mode to track the MPP rapidly. When the operation point reaches the MPP, the mode switches to the variable step mode to minimize the steady state error. In addition, the output disturbance is decreased through the optimization of the control method design. The performance of the proposed MPPT algorithm is verified through simulation and experiment.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1045-1049
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• 1996

For the precision positioning and tracking control, the proper friction compensation is essential. The friction causes steady state error. The friction compensation based on the velocity and the controlling input or the desired velocity provides limited performance if the compensation value is fixed. In this paper, a friction compensation scheme using a fuzzy logic is proposed. The friction compensation amount is adjusted depending on the velocity and controlling input. The proposed fuzzy friction compensator with a pole-assignment controller is implemented in a linear positioning system. To illustrate the effectiveness of this scheme, computer simulations and experiments are carried out for the cases of no friction compensation, the proposed fuzzy friction compensation, and another friction compensation scheme based on velocity and control input, and the results are compared with each other.