• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1029-1031
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• 1999

This paper presents an $H_{\infty}$ based robust STATCOM supplementary controller design to suppress the SSR in series-compensated line. This controller is designed to have the robust stability against the plant model uncertainty. Time domain simulations using a nonlinear system model show that the proposed STATCOM supplementary controller can suppress the SSR efficiently against the plant model uncertainty

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.301-305
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• 1996

$\mu$ theory can handle the parametric uncertainty and produces more non-conservative controller than H$_{\infty}$ control theory. However an existing solution of the theory, D-K iteration, creates a controller of huge order and cannot handle the real or mixed real-complex perturbation sets. In this paper, we use genetic algorithms to solve these problems of the D-K iteration method. The Youla parameterization is used to obtain all stabilizing controllers and the genetic algorithms determines the values of the state feedback gain, the observer gain, and Q parameter to minimize $\mu$, the structured singular value, of given system. From an example, we show that this method produces lower order controller which controls a real parameter-perturbed plant than D-K iteration method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.3
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• pp.136-141
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• 2000

This paper presents the design of an H$\infty$ based robust Static Synchronous Compensator (STATCOM) supplementary controller to suppress the subsynchronous resonance (SSR) in the series-compensated system. The IEEE second benchmark, System-l model is employed for this study. In order to design the effective controller, the modal controllability and observability indices to the oscillation modes are considered. Comprehensive time domain simulations using a nonlinear system model that the proposed STATCOM supplementary controller can suppress the SSR efficiently in spite of the variations of power system operating conditions.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.452-457
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• 2003

An add-on type output regulator is proposed in this paper. By an add-on controller we mean an additional controller which operates harmonically with a pre-designed one. The role of the add-on controller is to reject a sinusoidal disturbance of unknown magnitude and phase but with known frequency. Advantages of the proposed controller include that (1) it can be used only when the performance of disturbance rejection needs to be enhanced, (2) when it is turned on or off, unwanted transient can be avoided (i.e., bumpless transfer), (3) it is designed for perfect disturbance rejection not just for disturbance reduction, (4) ability for perfect rejection is preserved even with uncertain plant model. This design may be promising for optical disc drive (ODD) systems in which disc eccentricity results in a sinusoidal disturbance. For ODD systems, the sensitivity function obtained by the pre-designed controller, which may have been designed by the lead-lag, $H_{\infty}$, or DOB (disturbance observer) technique, does not change much with the add-on controller except at the frequency of the disturbance. Since the add-on controller does the job of rejecting major eccentricity disturbance, the gain of the pre-designed controller does not have to be too high.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.5
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• pp.617-623
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• 2010

In this research an LMI based mixed $H_2/H_{\infty}$ controller for a Wheeled Inverted Pendulum is designed and a numerical simulation of that is carried out. The Wheeled Inverted Pendulum is a kind of an inverted pendulum that has two equivalent points. To keep that the naturally unstable equivalent point, a controller should control the wheels persistently. Dynamic equations of the Wheeled Inverted Pendulum are derived with considering inclined road that is one of the representative road conditions. A Linear Matrix Inequality method is used to construct a controller that is able to stabilize the Wheeled Inverted Pendulum with considering the inclined road condition aggressively. Various numerical simulations show that the LMI based controller is doing well on not only flat road but also inclined road condition.

• Smart Structures and Systems
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• v.22 no.5
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• pp.547-560
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• 2018

This paper investigates the operation of the $H_{\infty}$ static output-feedback controller to reduce dynamic responses under seismic excitation on the five-story and benchmark 20 story building with parametric uncertainties. Linear matrix inequality (LMI) control theory is applied in this system and then to achieve the desired LMI formulations, some transformations of the LMI variables is used. Conversely uncertainties due to material properties, environmental loads such as earthquake and wind hazards make the uncertain system. This problem and its effects are studied in this research. Also to decrease the transition of large amount of data between sensors and controller, avoiding the disruption of whole control system and economy problems, the operation of the decentralized controllers is investigated in this paper. For this purpose the comparison between the performance of the centralized, fully decentralized and partial decentralized controllers in uncoupled and coupled cases is performed. Also, the effect of the changing the number of stories in substructures is considered. Based on the numerical results, the used control algorithm is very robust against the parametric uncertainties and structural responses are decreased considerably in all the control cases but partial decentralized controller in coupled form gets the closest results to the centralized case. The results indicate the high applicability of the used control algorithm in the tall shear buildings to reduce the structural responses and its robustness against the uncertainties.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.1
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• pp.33-41
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• 2002

In this paper, we present a frequency weighted model reduction using LMIs for minimizing the H$\infty$ weighted model error compared with the methods of frequency weighted balanced truncation and frequency weighted Hankel norm approximation. The proposed algorithm, its form is equal to the sufficient condition of performance preserving controller approximation, is based on an iterative two-step LMI scheme induced from bound real lemma. So, it can be applied to the problem of the performance preserving controller approximation. The controller reduction is useful in a practical control design and ensures its easy implementation and high reliability The validity of the proposed algorithm is shown through numerical examples. Additionaly, we extend the proposed algorithm to performance preserving controller approximation by applying to the HIMAT(highly maneuverable aircraft technology) system.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.86-92
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• 1998

This paper deals with an output feedback H control problem for linear time ivariant systems with state delay. The proposed output feedback controller is represented by the lower linear fractional transformation of alinear time invariant system and a delay operator. Sufficient conditions for the existence of the output feedback controller are given in the form of linear matrix inequalities which are less conservative than those for the existence of a rational output feedback controler. We also present a numerical example to demonstrate the efficacy of the proposed method.of the proposed method.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.974-976
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• 1996

In this paper, a reference model following control system using a fuzzy logic controller(FLC) is proposed By using an integrator and a nonlinear hysteresis element, a reference model whose response has no overshoot and fast rise time is designed. A FLC is designed to follow as close as possible to the response of the reference model. The proposed design method is shown that the robustness and the optimal tracking property can be achieved under modeling error, disturbance and parameter perturbations. The effectiveness of the proposed design method is verified through the simulation that compare using the FLC with using a $H_{\infty}$ controller.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1116-1118
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• 1996

This paper designs a digital controller by making use of the $H^{\infty}$ control algorithm and $\mu$-synthesis in order to keep a balance of the VTOL(Vertical Take Off and Landing Plane) vehicle with 4 fans. A identification of the actual model is acquired by the vehicle rolling, pitching and yawing angles for a pseude-random signal input and various identification theories. In spite of parameter variations and existing disturbances, the designed controller showes its robust performance through simulations and experiments.