• Journal of Institute of Control, Robotics and Systems
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• v.11 no.9
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• pp.741-749
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• 2005

This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, a dead-zone nonlinear element is used for the nonlinear controller and a PID control method is used for the linear controller. Although this parallel structure of the controller improves anti-shock performance, it has a narrow stability bound. In this paper, the dead-zone with saturation nonlinear element is proposed for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher slope gain of dead-zone than that of nonlinear controller using dead-zone only. In the linear controller design, it is shown that the lead-lag control has an improved stability margin over PID control. Numerical simulation results and experimental results show that the proposed method can get better performance to the external shock than previously proposed methods.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.69-77
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• 2011

In this paper, an optimal PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(ERA) systems with system uncertainties and saturation in the motor. An ERA prototype is developed and system modeling and parameter identification are executed. Then, optimal PID and optimal anti-windup PID controller are designed based on identified system model by using optimization toolbox in MA TLAB/Simulink and the performance of the two control systems are compared by experiment. It was found that the optimal anti-windup PID control system has better performance than the optimal anti-windup PID control system.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.141-150
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• 1998

This paper presents a dynamical anti-reset windup (ARW) compensation method for saturating control systems with multiple controllers and/or multiloop configuration. By regarding the difference of controller states in the absence and presence of saturating actuators as an objective function, the dynamical compensator which minimizes the objective function is derived in an integrated fashion. The proposed dynamical compensator is a closed form of plant and controller parameters. The resulting dynamics of compensated controller reflects the linear closed-loop system. The proposed method guarantees total stability of the resulting system. The effectiveness of the proposed method is illustrated by applying it to a servo motor control system. The paper is an extension of the results in Park and Choi[1].

• Journal of Power System Engineering
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• v.17 no.4
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• pp.120-130
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• 2013

An adaptive PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(EHA) systems with system uncertainties and saturation in the motor. An EHA prototype is developed and system modeling and parameter identification are executed. Then, adaptive PID sliding mode controller and optimal anti-windup PID controller are designed and the performance and robustness of the two control systems are compared by experiment. It was found that the adaptive PID sliding mode control system has better performance and is more robust to system uncertainties than the optimal anti-windup PID control system.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.134-139
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• 2007

A delivery ship is used to handle the cargo with the crane to/from the ships. The ship is inclined in the direction of a cargo which is hung on a crane. In this case, a arc shaped rail should be in the equilibrium state to get good anti-rolling performance. In this study, a device and control algorithm are developed to take accurate and quick equilibrium of the rail. The device is composed of a hinged immovable support, screw jack and damper. And the control system is based on I-PD control law to consider of control input saturation and overshoot. The controller is composed of integral controller of feedforward path and proportional-derivative controller of feedback path. The parameters of controller is designed to follow the reference signal and to remove overshoot. The simulation results show that the desirable control performance is achieved.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.333-342
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• 2020

Power exchanges between the grid and the battery through a bidirectional DC-DC converter are essential for DC microgrid systems. In general, the battery is charged when the grid is connected, and the system is powered by the battery when the grid is disconnected. In this mode transition, the saturation of the voltage controller slows down output response and produces large transient errors in DC link voltage. To solve this problem, a novel anti-windup design is proposed to improve anti-windup performance further. The proposed method stabilizes DC bus voltage through a wider range of battery voltage with faster transition compared with that of conventional methods. The proposed method is verified through an experimental setup composed of a 125 W laboratory-scale DC microgrid system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.545-551
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• 2011

Recently, demands for generating high quality tap waters are increasing with high concern of water pollution and corrosion of water pipelines. For the reasons, developing water quality stabilization technique in water purification system is sought rather than replacing to a new pipelines. In this study, high-purity liquid lime($Ca(OH)_2$) was introduced for a water quality stabilization technique in water purification process and simulated water distribution system of pilot-scale size was applied to evaluate anti-corrosion control effect. The effect of anti-corrosion control was calculated in terms of LSI(Langelier Saturation Index) In conclusion, the result of pilot plant showed improvement of corrosiveness by liquid lime($Ca(OH)_2$) with reduction of released iron(Fe). Application of anti-corrosion control technique to the mild steel coupon and the copper coupon were effective by indicating 35.4, 44.5% of improvements. Besides, sample pipes which were treated with liquid lime had formated more thicker layer of corrosion product inside of pipes. As a result, the process of injecting water stabilizer can greatly contribute to the high quality of tap water.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.444-444
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• 2011

Recently, patterned magnetic films and elements attract a wide interest due to their technological potentials in ultrahigh-density magnetic recording and spintronic devices. Among those patterned magnetic structures, magnetic anti-dot patterning induces a strong shape anisotropy in the film, which can control the magnetic properties such as coercivity, permeability, magnetization reversal process, and magneto-resistance. While majority of the previous works have been concentrated on anti-dot arrays with a single magnetic layer, there has been little work on multilayered anti-dot arrays. In this work, we report on study of the magnetic properties of bilayered anti-dot system consisting of upper perforated Co layer of 40 nm and lower continuous Ni layer of 5 nm thick, fabricated by photolithography and wet-etching processes. The magnetic hysteresis (M-H) loops were measured with a superconducting-quantum-interference-device (SQUID) magnetometer (Quantum Design: MPMS). For comparison, investigations on continuous Co thin film and single-layer Co anti-dot arrays were also performed. The magnetic-domain configuration has been measured by using a magnetic force microscope (PSIA: XE-100) equipped with magnetic tips (Nanosensors). An external electromagnet was employed while obtaining the MFM images. The MFM images revealed well-defined periodic domain networks which arise owing to the anisotropies such as magnetic uniaxial anisotropy, configurational anisotropy, etc. The inclusion of holes in a uniform magnetic film and the insertion of a uniform thin Ni layer, drastically affected the coercivity as compared with single Co anti-dot array, without severely affecting the saturation magnetization ($M_s$). The observed changes in the magnetic properties are closely related to the patterning that hinders the domain-wall motion as well as to the magneto-anisotropic bilayer structure.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.5
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• pp.380-387
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• 1989

The Conventional-Anti-reset-Windup (CAW) structure gives pretty good performance among the conventional strategies that prevent systems from saturation, but there is no systematic way of designing the control systems. Also, it frequently destabilizes the systems. Moreover, the CAW structure cannot be applied when the output of the saturating actuator cannot be measured. Therefore the CAW structure is modified to accommodate this situation. An effective designing method is proposed to give better performance of the control system. The stability of the control system is also considered. The usefulness of the proposed method is shown by applying this method to a few examples.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.3
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• pp.447-457
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• 1994

This paper presents a compensation method for discrete-time control systems with saturation nonlinearities to cope with the reset windup phenomena. The proposed ARW (Anti-Reset Windup) method is motivated by the concept of the equilibrium point. The design parameter of the ARW scheme is explicitly derived by minimizing a reasonable performance index. The resulting dynamics of the compensated controller exhibits the reduced model form of the unsaturated system which can be obtained by the singular perturbational model reduction method. An example is given to illustrate the effectiveness of the proposed method.