• Journal of Power Electronics
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• v.19 no.3
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• pp.655-664
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• 2019

In order to analyze the nonlinear phenomena of the bifurcation and chaos caused by the switching of nonlinear switching devices in inductively coupled power transfer (ICPT) systems, a Jacobian matrix model, based on discrete mapping numerical modeling, is established to judge the system stability of the periodic closed orbit and to study the nonlinear behavior of Hopf bifurcation in a system under full resonance. The general flow of the parameter design, based on the stability principle for ICPT systems, is proposed to avoid the chaos and bifurcation phenomena caused by unreasonable parameter selection. Firstly, based on the state equation of SS-type compensation, a three-dimensional bifurcation diagram with the coupling coefficient as the bifurcation parameter is established with a numerical simulation to observe the nonlinear phenomena in the system. Then Filippov's method based on a Jacobian matrix model is adopted to deduce the boundary of stable operation and to judge the type of the bifurcation in the system. Then the general flow of the parameter design based on the stability principle for ICPT systems is proposed through the above analysis to realize stable operation under the conditions of weak coupling. Finally, an experimental platform is built to confirm the correctness of the numerical simulation and modeling.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.11
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• pp.577-584
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• 2002

This paper presents a novel approach based on eigenvalue perturbation of augmented matrix(AMEP) to estimate the eigenvalue for variation of controller parameter. AMEP is a useful tool in the analysis and design of large scale power systems containing many different types of exciters, governors and stabilizers. Also, it can be used to find possible sources of instability and to determine the most sensitivity parameters for low frequency oscillation modes. This paper describes the application results of AMEP algorithm with respect to all controller parameter of KEPCO systems. Simulation results for interarea and local mode show that the proposed AMEP algorithm can be used for turning controller parameter, and verifying system data and linear model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.963-968
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• 2006

The main purpose of this paper is to investigate the stability of water tower with a relatively small footing. The water tower is modeled that the column carrying a container is supported by a rotational spring at the base and is of constant cross-section, with a weight per unit length of column axis. The column model is based on the Bernoulli-Euler beam theory. The Runge-Kutta method and Determinant Search method are used to perform the integration of the governing differential equation and to determine the critical values(critical own weight. and critical buckling load), respectively. The critical buckling loads are calculated over a range of system parameters: the rotational stiffness parameter, the dimensionless radius of container and the own weight parameter of the column. The relation between the rotational stiffness parameter and the critical own weight parameter of the column is analyzed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.590-595
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• 1996

The robust control technique is generally the iterative design method to determine a robust control for perturbed system with prescribed range of perturbation based on the robust stability measure. However, robot manipulator has the structured pertubation and the unstructured one. This paper proposes the robust technique for designing controller such that the trajectory of end-effector of robot manipulator tracks asymptotically the desired trajectory for all allowable variations in the manipulator's parameter. For satisfying asymptotical stability though we can not know the bound of perturbations and the parameter variations, the relation between the unknown parameter and the parameter of nominal system can be derived from Krasovskii theorem and we construct the new robust control using that relation. (author). 12 refs., 6 figs.

• Smart Structures and Systems
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• v.9 no.4
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• pp.373-392
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• 2012

Tracking control of systems with variable stiffness hysteresis using a gain-scheduled (GS) controller is developed in this paper. Variable stiffness hysteretic system is represented as quasi linear parameter dependent system with known bounds on parameters. Assuming that the parameters can be measured or estimated in real-time, a GS controller that ensures the performance and the stability of the closed-loop system over the entire range of parameter variation is designed. The proposed method is implemented on a spring-mass system which consists of a semi-active independently variable stiffness (SAIVS) device that exhibits hysteresis and precisely controllable stiffness change in real-time. The SAIVS system with variable stiffness hysteresis is represented as quasi linear parameter varying (LPV) system with two parameters: linear time-varying stiffness (parameter with slow variation rate) and stiffness of the friction-hysteresis (parameter with high variation rate). The proposed LPV-GS controller can accommodate both slow and fast varying parameter, which was not possible with the controllers proposed in the prior studies. Effectiveness of the proposed controller is demonstrated by comparing the results with a fixed robust $\mathcal{H}_{\infty}$ controller that assumes the parameter variation as an uncertainty. Superior performance of the LPV-GS over the robust $\mathcal{H}_{\infty}$ controller is demonstrated for varying stiffness hysteresis of SAIVS device and for different ranges of tracking displacements. The LPV-GS controller is capable of adapting to any parameter changes whereas the $\mathcal{H}_{\infty}$ controller is effective only when the system parameters are in the vicinity of the nominal plant parameters for which the controller is designed. The robust $\mathcal{H}_{\infty}$ controller becomes unstable under large parameter variations but the LPV-GS will ensure stability and guarantee the desired closed-loop performance.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.185-190
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• 1991

In this paper, we present a method of analising a system with nonlinear parameter by pole sensitivity defined by the rate of pole movement with respect of non-linear parameter variation. Pole sensitivity give us not only the rate of pole movement but also the directional information. We present a method of design of a state feedback for a system with nonlinear system parameter by considering the pole sensitivity and show that the suggested method guarantee the stability robustness for a system with nonlinear parameter, parameter perturbation and urimodelled dynamics.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.535-535
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• 2000

This paper presents an adaptive receding horizon H$_{\infty}$ controller for the linear parameter varying systems in the deterministic environment, which combines a parameter range estimator and a robust receding horizon H$_{\infty}$ controller using the parameter bounds. Using parameter set inclusion and terminal inequality condition, the closed-loop system stability is guaranteed. It is shown that the stabilizing adaptive receding horizon H$_{\infty}$ controller guarantees the H$_{\infty}$ norm bound.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.206-214
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• 2013

This paper proposes a new method for monitoring local voltage stability using the saddle node bifurcation set or loadability boundary in two dimensional power parameter space. The method includes three main steps. First step is to determine the critical buses and the second step is building the static voltage stability boundary or the saddle node bifurcation set. Final step is monitoring the voltage stability through the distance from current operating point to the boundary. Critical buses are defined through the right eigenvector by direct method. The boundary of the static voltage stability region is a quadratic curve that can be obtained by the proposed method that is combining a variation of standard direct method and Thevenin equivalent model of electric power system. And finally the distance is computed through the Euclid norm of normal vector of the boundary at the closest saddle node bifurcation point. The advantage of the proposed method is that it gets the advantages of both methods, the accuracy of the direct method and simple of Thevenin Equivalent model. Thus, the proposed method holds some promises in terms of performing the real-time voltage stability monitoring of power system. Test results of New England 39 bus system are presented to show the effectiveness of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1663-1666
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• 1997

The purpose of this paper is to find how to determine the controllability and stability derivatives form flight test and to display the stability of the Twinbee aircraft. There are various methods developed to find the derivatives : wind tunnel testing, predicted result from empirical data, flight test and so on. Among those methods, the estimation form flight test of real aricraft is the most reliable. We performed the flight test of Twinbee and recorded the states of aorcraft. Using those states and parameter setimation algorithem based on the Maximum Likdlihood(MMLE) criterion, we can estimate the controllability and stability derivatives. In this paper, wel will show the process form designing the proper flight test input to estimation of derivatives.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.3
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• pp.215-220
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• 2008

This study examined the stability of cross- and box-type artificial reefs used to construct seaweed beds. Theoretical and experimental studies have clarified the Froude similitude. However, basic data needed to develop a more stable design for artificial reefs must be collected from long-term studies and analyses of sliding caused by waves. Hydraulic experiments are important for solving problems in the design and construction of artificial reefs. This study examined some design parameters for artificial reefs under wave and currents. The results showed the stability of cross- and box-type artificial reefs for constructing seaweed beds using a dimensionless parameter (the surf similarity parameter), water particle velocity, and so on. The hydraulics experiment indicated that the stability of artificial reefs differed according to their method of installation. This implies that artificial reefs should be installed after considering various environmental factors, such as wave breaking, reflection, and sediments.