• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.389-395
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• 2007

In this paper, we consider the robust non-fragile $H_{\infty}$ output feedback controller design method for uncertain descriptor systems with feedback and observer gain variations. The existence condition of observer-based robust and non-fragile $H_{\infty}$ output feedback controller and the controller design method are Presented on the basis of linear matrix inequality approach. The proposed robust non-fragile $H_{\infty}$ output feedback controller guarantees asymptotic stability, non-fragility, $H_{\infty}$ norm bound within a prescribed level in spite of disturbance, parameter uncertainty, and feedback/observer gain variations.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.5
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• pp.63-70
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• 1993

In 1980's to 1990's the marine propulsion diesel engines have been developed into lower speed and longer stroke for the energy saving(small S.F.O.C.). As these new trends the convetional mechnical-hydraulic governors were not adapted to the new requirements and the digital governors have been adopted in the marine use. The digital governors usually use the control algorithms such as the PID control, optimal control, adaptive control and etc. While the engine has delay time and parameter variations these control algorithms have difficulty in considering the stability and the robustness for the model uncertainty. In this study, the $H_{\infty}$ controller design method are applied to the speed control of the low speed marine diesel engine. By comparison the $H_{\infty}$ control results with the PID control results, the validity of the $H_{\infty}$ controller under the delay time and parameter variations is confirmed.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.970-972
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• 1998

In this paper, the standard Dole, Glover, Khargoneker, and Francis (abbr. : DGKF 1989) $H_{\infty}$ controller $(H_{\infty}C)$ is extended to the nonlinear feedback linearization-$H_{\infty}$ /sliding mode controller (NFL-$H_{\infty}$/SMC) to solve the problem associated with the full state feedback for the unmeasurable state variables in the conventional SMC, to obtain the smooth control as the linearized controller for a linear system (or to cancel the nonlinearity for the nonlinear system), and to improve the time-domain performance under worst case.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.994-996
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• 1998

In this paper, the standard Dole, Glover, Khargoneker, and Francis (abbr. : DGKF 1989) $H_{\infty}$ controller $(H_{\infty}C)$ is extended to the nonlinear feedback linearization-$H_\infty$-based sliding mode controller (NFL-$H_\infty$-based SMC). A stability proof of the closed-loop stability is done by a Lyapunov function candidate using an addition form of the sliding surface vector and the estimation error.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.529-536
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• 2000

A robust controller to attenuate the various disturbances of tandem cold mills (TCM) is synthesized by measurement-feedback $H_{\infty}$ control techniques which can reflect the input direction of disturbances and the knowledge of entry thickness variation (disturbance) is synthesized by discrete-time measurement-feedback $H_{\infty}$ control theory. It is demonstrated that the $H_{\infty}$ preview control gain can be easily obtained by the seperation principle of the control and estimation problems in $H_{\infty}$ control. Finally the effectiveness of the proposed control method for TCM is evaluated by the computer simulation and compared to the other control methods which have been previously studied.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.151-156
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• 1998

This paper presents an $H_{\infty)$ output feedback controller design method for linear systems with delayed state, delayed control input, and delayed masurement output. Using a Lyapunov functional, the stability for delayed systems is discussed independently of delays. Also, sufficient condition for the existence of $H_{\infty)$ controllers of any order is given in terms of three linear matrix inequalities(LMIs). Based on positive definite solutions of their LMIs, we briefly explain the way to construct $H_{\infty)$ controller, which stabilizes time-delay systems independently of delays and guarantees an $H_{\infty)$norm bound.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.936-938
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• 1996

The $H_{\infty}$ robust controller is designed for on-line adaptive control application by using polynomial approach. The $H_{\infty}$ robust controllers for adaptive system were designed first by Grimble. But they have a problem that two minimum costs can exist and did not minimize the conventional $H_{\infty}$ cost function which is the $H_{\infty}$ sum of weighted sensitivity and complementary sensitivity terms. In this paper, the two minimum costs problem can be avoided and the conventional $H_{\infty}$ cost function is minimized by employing the Youla parameterization and polynomial approach at the same time. In addition pole placement is possible without any relation with weighting function.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.78-86
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• 1995

$H_{\infty}$ Controller of seeker scan-loop is designed using LSDP proposed by McFarlane. The performance and robustness of $H_{\infty}$ controller are analyzed using robustness theorems by Lehtomaki and compared with those of the LQG/LTR controller. Especially, structured singular value .mu. -test of Doyle is used to evaluate robust performance of seeker scan-loop. It is demonstated that seeker scan-loop by $H_{\infty}$ controller is very robust to model uncertainties described by additive and multiplicative perturbations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.172-179
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• 2003

Linear matrix Inequality based $H_\infty$ robust controller is designed to control the motion of a 4-axis unbalanced rigid asymmetric rotor supported and controlled by two active magnetic bearings in this paper. To this end, the equations of motion of the system are derived via Hamilton's variational principle and transformed to a state-space form for the standard $H_\infty$ control problem. LMI-based controller, which does not require additional assumptions beyond the usual stabilizability and detectability assumptions, is designed based upon the pole place weighting function and loopshaping technique. The obtained results are compared with those reported in the available literature and the efficiency of the proposed LMI-based $H_\infty$ control is revealed.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.126-132
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• 2012

This paper suggests a design method of the model-following H${\infty}$ control system having robust performance. This H${\infty}$ control system is designed by applying genetic algorithm(GA) with reference model to the optimal determination of weighting functions and design parameter ${\gamma}$ that are given by Glover-Doyle algorithm which can design H${\infty}$ controller in the state space. These weighting functions and design parameter ${\gamma}$ are optimized simultaneously in the search domain guaranteeing the robust performance of closed-loop system. The effectiveness of this H${\infty}$ control system is verified by applying to the boiler-turbine control system.