• Journal of Power Electronics
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• v.12 no.3
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• pp.410-417
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• 2012

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.3
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• pp.335-340
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• 2008

In this paper, a decentralized fuzzy output feedback controller for nonlinear interconnected systems with time delay is proposed. The nonlinear interconnected system is represented to fuzzy system using Takagi-Sugeno (T-S) fuzzy model. The decentralized output feedback controller is designed(or stability of subsystems of the fuzzy interconnected system. The stable condition of the closed-loop subsystem is represented to the linear matrix inequality (LMI) form and control gain is obtained by LMI. An example is given to show the verification discussed throughout the paper.

• Advances in Computational Design
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• v.8 no.3
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• pp.237-253
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• 2023

Torque ripple content and variable switching frequency operation of conventional direct torque control (DTC) are reduced by the integration of space vector modulation (SVM) into DTC. Integration of space vector modulation to conventional direct torque control known as SVM-DTC. It had been more frequently used method in renewable energy and machine drive systems. In this paper, SVM-DTC is used to control the rotor side converter (RSC) of a wind driven doubly-fed induction generator (DFIG) because of its advantages such as reduction of torque ripples and constant switching frequency operation. However, flux and torque ripples are still dominant due to distorted current waveforms at different operations of the wind turbine. Therefore, to smoothen the torque profile a Neural Network Controller (NNC) based SVM-DTC has been proposed by replacing the PI controller in the speed control loop of the wind turbine controller. Also, stability analysis and simulation study of DFIG using process reaction curve method (RRCM) are presented. Validation of simulation study in MATLAB/SIMULINK environment of proposed wind driven DFIG system has been performed by laboratory developed prototype model. The proposed NNC based SVM-DTC yields superior torque response and ripple reduction compared to other methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.508-517
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• 2005

This paper describes a high performance voltage controller for 3-phase 4-wire UPS (Uninterruptible Power Supply) system, and proposes a new scheme of synchronous reference frame controller in order to compensate for the voltage distortions due to unbalanced and nonlinear loads. Proposed scheme can eliminate the negative sequence voltage component due to unbalanced loads and also reduce the harmonic voltage component due to non-linear loads, even when the bandwidth of voltage control loop is a very low. In order to compensate for the effects of unbalanced loads, the synchronous reference frame controller with the positive and negative sequence computation block is proposed, and the synchronous frame controller with a bandpass filter is proposed to compensate for the selected harmonic frequency of output voltage. The effectiveness of the proposed scheme has been investigated and verified through computer simulations and experiments by a 30kVA UPS.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.32-39
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• 1997

One of the most important performance criteria in tuning the gain of position loop controller for CNC machining center is the contour error. In this papre we analyze contour error in the linear and circular interpolations for the axis-matched and mismatched cases. To have small contour errors, it is necessary to set the P gain for each axis to be same. And the D gain should be much smaller than the P gain. Baded on the analysis in the frequency domain, we propose a gain tuning method for the P and PD controllers. We show that the PD controller is better than the P controller. The effectiveness of this method is demonstrated by experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.235-241
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• 2020

In this paper, we propose the bus/bypass synchronization phase lock loop (B-Sync PLL) method using each phase voltage controller of a parallel UPS inverter. The B-Sync PLL included in each phase voltage control system of parallel UPS inverters has the transient response and the phase synchronization error at grid normal or blackout. The validity of this method is verified by simulation and experiment. As a result, the parallel UPS inverters using the proposed method confirmed that the output phase was continuously synchronized when a grid blackout, improving the transient response characteristics for stable load power supply and equal load sharing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.637-643
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• 2010

The paper is about the development of 6-DOF active vibration isolation systems using VCM. Firstly, formulate the vertical 3-DOF mathematical model under eccentric load, and compare the model with the case in which the center of mass is located at the centroid. And then, complete the 6-DOF mathematical model by formulating the horizontal 3-DOF mathematical model. Find main parameters by comparing the result of the frequency response test with simulation result on the model. Finally, achieve the performance of vibration isolation by applying loop shaping approach & feedforward controller.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.222-228
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• 2012

This paper presents a design and simulation of bi-directional DC/DC boost converter for a fuel cell system. In this paper, we analyze the equivalent model of both a boost converter and a buck converter. Also we propose the controller of bi-directional DC-DC converter, which has buck mode of charging a capacitor and boost mode of discharging a capacitor. In order to design a controller, we draw bode plots of the control-to-output transfer function using specific parameters and incorporate 3pole-2zero compensator in a closed loop. As a result, it has increased PM(Phase Margin) for better dynamic performance. The proposed bi-directional DC-DC converter's 3pole-2zero compensation method has been verified with computer simulation and simulation results obtained demonstrates the validity of the proposed control scheme.

• The Journal of Korea Robotics Society
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• v.15 no.3
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• pp.212-220
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• 2020

This paper deals with a strategy of gain optimization for the kinematic control algorithm of a wire-driven surgical robot. The proposed controller consists of the closed-loop inverse kinematics with the back-calculation method. The closed-loop inverse kinematics has 18 PID control gains, and the back-calculation method has 6 gains. An efficient strategy is designed to optimize 18 values first and then the remaining 6 values. The optimal gain sets are searched under the step input with performance indices. In this gain optimization, the objective function is defined as the minimum value of signal-to-noise ratio of the performance indices for 6 DoF (Degree-of-Freedom) motion that is based on the Taguchi method, and the constraints are applied to obtain stable responses for each motion evenly. The gain sets obtained are verified by simulations using the test trajectories. In comparative results, the optimal gain value based on the performance index combined with ISE (integral of square error) and settling time showed the best control performance.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.30-37
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• 2004

This thesis develops a fuzzy-PID control algorithm for control the filament winding tension. It is developed by applying classical PID control technique to a fuzzy logic controller. It is composed of a fuzzy-PI controller and a fuzzy-D controller. The fuzzy-PI controller uses error and integrated error as inputs, and the fuzzy-D controller uses derivative of error as input. The fuzzy-PI controller uses Takagi-Sugeno fuzzy inference system, and the fuzzy-D controller uses Mamdani fuzzy inference system. The fuzzy rule base for the fuzzy-PI controller is designed using 19 rules, and the fuzzy rule base for the fuzzy-D controller is designed using 5 rules. A test-bed is set-up for verifying the effectiveness of the developing control algorithm in control the filament winding tension. It is composed of a mandrel, a carriage, a force sensor, a driving roller, nip rollers, a creel, and a real-time control system. Nip rollers apply a vertical force to a filament, and the driving roller drives it. The real-time control system is developed by using MATLAB/xPC Target. First, experiments for showing the inherent problems of an open-loop control scheme in a filament winding are performed. Then, experiments for showing the robustness of the developing fuzzy-PID control algorithm are performed under various working conditions occurring in a filament winding such as mandrel rotating speed change, carriage traversing, spool radius change, and reference input change.