• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.10
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• pp.495-501
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• 2002

A difference based current transformer (CT) saturation detection algorithm uses the third difference of a secondary current to detect the instants of the beginning/end of saturation. The third difference of a secondary current contains high frequency components when a CT is saturated. Thus, an effect of an anti-aliasing lowpass filter implemented in digital protection relays on the detection algorithm should be studied. This paper describes performance analysis of a lowpass filter on the CT saturation detection algorithm. The cutoff frequency of the lowpass filter is normally set to be half of a sampling frequency. In this Paper, two sampling frequencies of 3,840 (Hz) corresponding to 64 sample/cycle (s/c) and 1,920 (Hz) corresponding to 32 (s/c) are studied; the cutoff frequencies of the lowpass filters are set to be 1,920 (Hz), 960 (Hz) and 960(Hz), 480(Hz), respectively. And the proposed algorithm is verified by experiment. A 2nd order Butterworth filter is designed as a lowpass filter. The test results and experiment results clearly indicate that the saturation detection algorithm successfully detects the instants of the beginning/end of saturation even though a secondary current is filtered by the designed lowpass filters.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.975-980
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• 2004

Positioning system is widely used for many practical applications. This system requires a good controller to achieve high accuracy and fast response with simple and self-adjustable design. In order to satisfy the above requirements, a new practical controller for positioning systems, namely nominal characteristic trajectory following (NCTF) controller with PI compensator, has been proposed. However, the effect of actuator saturation can not be completely compensated for integrator windup when the object parameters vary. This paper presents a method to improve the NCTF controller by overcoming the problem of integrator windup by adopting a fuzzy system. The improvement of the NCTF controller is evaluated through simulation using a rotary positioning system. The simulation result has demonstrated the effectiveness of the compensated NCTF in overcoming the problem of integrator windup.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2616-2628
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• 1994

Recently the Time Delay Control(TDC) method has been proposed as a promising technique in the robust control area, where the plant has unknown dynamics with parameter variations and substantial disturbances are present. When TDC is applied to the plant with saturation nonlinearity, however, the so called windup phenomena are observed to arise, causing excessive overshoot and instability. In order to solve this problem, we have proposed an anti-windup method for TDC. The stability of the overall system has been analyzed for a class of LTI MIMO system. The effectiveness for the proposed method has been shown with simulation and experiment results.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.189-194
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• 1993

This paper presents an ARW(Anti-Reset Windup) method for discrete-time control systems with saturation nonlinearites. The method is motivated by the concept of the equilibrium point. The design parameters of the ARW scheme is explicitly derived by minimizing a reasonable performance index. The proposed method is closely related with the singular perturbed theory. The proposed method is applicable to any open-loop stable plants with saturation nonlinearities whose controllers are determined a priori by some design technique.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.430-437
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• 2020

In this research, the anti-windup techniques for the cascade control system are newly developed. Cascade control system has an additional internal feedback control loop to reject disturbances better than the conventional control system. Remarkable difference between the conventional single-loop control system and the cascade control system is the interaction that the controller output saturation of the secondary control loop strongly affects the integral action of the primary control loop. In industry, local back calculation anti-windup method has been mainly used for each controller without considering the interaction between the two controllers. But it cannot eliminate the integral-windup of the primary controller originated from the saturation of the secondary controller output. To solve the problem, the two anti-windup techniques of the cascade conditional integration and the cascade back calculation are proposed in this research by extending the local anti-windup techniques for the single-loop control system to the cascade control system. Simulation confirmed that the proposed methods can effectively remove the integral windup of the primary controller caused by the saturation of the secondary controller output and show good control performances for various types of processes and controllers. If the reliability of the proposed methods is proved through the applications to real processes in the future, they would highly contribute to improving the control performances of the cascade control system in industry.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.675-677
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• 2004

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, dead-zone nonlinear element is used for nonlinear controller and PID control method is used for linear controller. Although this strategy improves anti-shock performance, it has a narrow stability bound. In this paper, we propose dead-zone with saturation nonlinear element for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher gain of dead-zone than the controller with dead-zone only. In the linear controller design, we show that lead-lag control has improved stability margin over PID control. Numerical simulation results show that the proposed method can get better performance to the external shock than previously proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.519-519
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• 2000

Since the dynamics of the slave manipulator with high reduction ratio joints is likely to be much slower than that of the master manipulator, the control input the slave manipulator is so frequently saturated. This paper proposes a bilateral teleoperation control scheme for 2-DOF manipulators with high reduction ratio joints, which can effectively compensate the control input saturation. In the proposed scheme, the controllers of the slave manipulator are designed with an anti-windup feature and forces caused by the saturation are reflected to the operator holding the operating handle of the master manipulator. When the control input of the slave manipulator is saturated, the master manipulator moves slowly file to tile reflected forces. In this way, the position tracking performance of the slave manipulator with high reduction ratio joints can be enhanced regardless of saturation. The proposed scheme is shown to give excellent position tracking performance through a series of experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1966-1971
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• 2005

Though several previous anti-windup techniques have been proposed, they are limited to linear systems or friction is not considered. Thus this paper proposes a compensation scheme for input-constrained robot systems with friction to cope with the windup phenomenon and shows its effectiveness by simulations. Given a feedback linearizing controller for a robot system designed without considering its input constraint, an additional dynamic compensator is proposed to account for the constraint. The dynamic anti-windup is based on the minimization of a reasonable performance index, and properties of the resulting closed-loop are presented.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2629-2634
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• 2013

Fisetin is a naturally occurring flavonoid with some anti-cancer and anti-inflammation capabilities. In this study, we perform docking studies between human c-Jun N-terminal kinase 1 (JNK 1) and fisetin and proposed a binding model of fisetin and JNK 1, in which the hydroxyl groups of the B ring and oxygen at the 4-position of the C ring play key roles in binding interactions with JNK. Fluorescence quenching and saturation-transfer difference (STD) NMR experiments showed that fisetin exhibits good binding affinity to JNK, $1.32{\times}10^8M^{-1}$. The anti-inflammatory activity of fisetin was also investigated. Fisetin significantly suppressed tumor necrosis factor, the NO production, and macrophage inflammatory cytokine release in LPS-stimulated RAW264.7 mouse macrophages. We found that the anti-inflammatory cascade of fisetin was mediated through the JNK, and cyclooxygenase (COX)-2 pathways. Our findings suggest the potential of fisetin as an anti-inflammatory agent.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1534-1544
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• 2002

The TDCSA(Time Delay Control with Switching Action) method, which consists of Time Delay Control(TDC) and a switching action of sliding mode control(SMC), has been proposed as a promising technique in the robust control area, where the plant has unknown dynamics with parameter variations and substantial disturbances are preset. When TDCSA is applied to the plant with saturation nonlinearity, however, the so-called windup phenomena are observed to arise, causing excessive overshoot and instability. The integral element of TDCSA and the saturation element of a plant cause the windup phenomena. There are two integral effects in TDCSA. One is the integral effect occurred by time delay estimation of TDC. Other is the integral term of an integral sliding surface. In order to solve this problem, we have proposed an anti-windup scheme method for TDCSA. The stability of the overall system has been proved for a class of nonlinear system. Experiment results show that the proposed method overcomes the windup problem of the TDCSA.