• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.94-99
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• 2012

This paper discusses a decentralized sampled-data control problem for large-scale nonlinear systems. The system is represented in Takagi-Sugeno's form. Next, we design a decentralized analog controller based on the overlapping decomposition technique. The final step is to apply the intelligent digital redesign scheme for converting the analog controller into the sampled-data one. Design condition is represented in terms of linear matrix inequalities. A simulation result is provided for the effectiveness of the proposed design method.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1783-1784
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• 2008

This paper presents a novel control technique to deal with networked control systems with neutral timedelay, which is known to highly degrade the control performance of the controlled system. The stability analysis and design method for a sampled-data fuzzy controller for discrete networked control systems (NCS). The neutral time-delay and sampling activity will complicate the NCS. And it make the stability analysis much more difficult than that for a continuous-time NCS. Based on the fuzzy control approach, linear matrix inequality (LMI)-based stability conditions are derived to guarantee the neutral T-S fuzzy system stability. The simulation results and practical experiments illustrate that the proposed controller design is realistic.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.381-388
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• 2018

A novel and simple algorithm for accurate calculation of RMS voltage is proposed in a digitally controlled grid-tie inverter system. Given that the actual frequency of grid voltage is continuously changing, the constant sampling frequency cannot be a multiple number of the fundamental frequency. Therefore, the RMS of grid voltage contains periodic oscillations due to the differences in the phase angle of sampled data during calculation. The proposed algorithm precisely calculates and updates the initial phase angle of the first sampled voltage in a half-cycle period using phase-locked loop, which is commonly utilized for phase angle detection in grid-tie inverter systems. The accuracy and dynamic performance of the proposed algorithm are compared with those of other algorithms through various simulations and experiments.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.30-35
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• 2008

In this paper, the application of power Quality monitoring based on Sampled Value(SV) which is introduced in the IEC61850 International Standard for substation communication are discussed. Firstly, while Merging Unit(MU) is designed as a process level device transmitting sensor data, the practical problems such as time delay compensation and optical fiber communication are encountered. Secondly, the Sampled Value message which is proper to a power quality monitoring system is presented. Because the power quality monitoring system requests less time-critical service compared to protection and control applications, the Sampled Value service message structure is introduced to improve efficiency. Lastly, the power quality monitoring server having various power quality analysis functions is suggested to verify the performance of Merging Unit With the diverse experiments, it is proved that the process bus distributed solution is flexible and economic for the power quality monitoring.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.13-18
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• 2007

In this paper, authors deal with an application of power quality monitoring using the Sampled Value which is described in the IEC61850 International Standard for substation communication. Firstly, while Merging Unit is designed as a process level device transmitting sensor data, the practical problems such as time delay compensation and optical fiber communication are issued. Secondly, the Sampled Value message which is proper to a power quality monitoring system is presented. Because the power quality monitoring system requests non time critical service comparing to protection and control applications, the Sampled Value service message structure is introduced to improve efficiency. At last, the power quality monitoring server having various power quality analysis functions is suggested to verify the performance of Merging Unit. With the diverse experiments, it is proved that the process bus distributed solution is flexible and economic for the power quality monitoring.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.5
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• pp.269-275
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• 2019

This paper addresses the control problem of cyber-physical systems under controller attack. A novel discontinuous Lyapunov functionals are employed to fully utilize sampled-data pattern which characteristic is commonly appeared in cyber-physical systems. By considering the limited resource of networks, cyber-attacks on the controller are considered randomly occurring and are described as an attack function which is nonlinear but assumed to be satisfying Lipschitz condition. Novel criteria for designing controller with robustness for cyber-attacks are developed in terms of linear matrix inequality (LMI). Finally, a numerical example is given to prove the usefulness of the proposed method.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.39-41
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• 1996

While the z-transform method is a basic mathematical tool to relate the signals only at the sampling instants in analyzing and designing sampled-data control systems, the modified z-transform which is a variation of the z-transform is widely used to represent the details of continuous signals between the sampling instants. Regarding the modified z-transform method, some properties were established to relate the modified z-transform to the regular z-transform. This paper will show that these properties, in their current forms, cause some analytic problems, when they are applied to the signals with discontinuities at the sampling instants, which accordingly limit their applications significantly. In this paper, those analytic problems will be investigated, and the theorems of the modified z-transform will be revised by adopting a new notation so that those can be correctly interpreted and used without any analytic problems in the analysis of sampled data systems. Also some useful schemes of applying the modified z-transform will be developed.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.4
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• pp.349-354
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• 2015

This paper presents the stability conditions of the Takagi-Sugeno (T-S) fuzzy sampled-data filter. The error system between the T-S fuzzy system and fuzzy filter is presented. In the sense of the Lyapunov stability analysis, the stability conditions are given, which can be represented in terms of linear matrix inequalities (LMIs). The proposed stability conditions utilize the different approach from the conventional methods, and have better performance than that of the conventional ones. The simulation example is given to show the effectiveness of the proposed method.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.95-112
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• 2005

This work concerns the stabilization of uninfected steady state of an ordinary differential equation system modeling the interaction of the HIV virus and the immune system of the human body. The control variable is the drug dose, which, in turn, affects the rate of infection of $CD4^{+}$ T cells by HIV virus. The feedback controller is constructed by a variant of the receding horizon control (RHC) method. Simulation results are discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.271-274
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• 2001

In this paper, optimal digital design is studied within the framework of sampled-data control theory. In particular, multirate discretization of analog controller is considered using an H$_2$optimality criterion. Solutions are obtained via multirate H$_2$optimization with a causality constraint due to the multirate structure. In design example, the comparison of the proposed methods is made with the conventional discretization methods, and demonstrate the superiority of the multirate design method.