• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.513-522
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• 2006

This paper considers a robust output feedback $H\infty$ controller design method for singular systems with time-varying delay in state and parameter uncertainty in system matrix by an LMI approach and observer based technique, which can be solved efficiently by convex optimization. The sufficient condition for the existence of controller and the controller design method are presented by strict LMI(linear matrix inequality) approach. Since the obtained condition can be expressed as an LMI form, all variables including feedback gain and observer gain can be calculated simultaneously by Schur complement and changes of variables.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.19-30
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• 1997

In this paper we design the optimal satellite-tracking antenna $H{\infty}$ control system using genetic algorithms. To do this, we give gain and dynamics parameters to the weighting functions and apply genetic algorithms 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 stability of closed-loop system. The effectiveness of this satellite-tracking antenna $H{\infty}$ control system is verified by computer simulation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.46-54
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• 1998

This paper presents a method for designing robust fuzzy $H^{\infty}$ controllers which stabilize nonlinear systems with parameter uncertainty adn guarantee an induced $L_{2}$ norm bound constraint on disturbance attenuation for all admissible uncertainties. Takagi and Sugeno's fuzzy models with uncertainty are used as the model for the uncertain nonlinear systems. Fuzzy control systems utilize the concept of so-called parallel distributed compensation(PDC). Using a single quadratic Lyapunov function, the stability condition satisfying decay rate and disturbance attenuation condition for Takagi and Sugeno's fuzzy model with parameter uncertainty are discussed. A sufficient condition for the existence of robust fuzzy $H^{\infty}$ controllers is then presented in terms of linear matrix inequalities(LMIs). Finally, design examples of robust fuzzy $H^{\infty}$ controllers for uncertain nonlinear systems are presented.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.248-251
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• 1991

A robust monitor AGC(Automatic Gauge Control) system for a hot strip mill plant of POSCO Is designed by minimizing the H.inf. norm of a so called mixed sensitivity function. In order to solve the mininizatlon problem, a polynomial approach proposed by Kwakernaak[5] is used. The controller performance is tested by a computer simulation under various circumstances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1144-1150
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• 2013

The stabilizing controller design problem of time-delay singularly perturbed systems is considered. The proposed approach is based on the $H_{\infty}$ norm and the composite control method. A sufficient condition for the stability of the time-delay slow subsystem is presented. Using this condition, we can construct the composite control law for the time-delay singularly perturbed system and analysis the system by the matrix Lambert W function. Illustrated examples are presented to demonstrate the validity and applicability of the proposed method.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.280-283
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• 2000

In this paper, a fault tolerant control problem is considered for a class of nonlinear system formulated in a gain scheduling form with LMI-based H-inf control technique Key benefits of this proposed scheme are demonstrated in the simulation of an electromagnetic suspension system with actuator and/or sensor failures, and the method is compared with the convensional state-feedback and output-feedback controller. It is clearly observed that the proposed control scheme shows an improved output performance in comparision with convensional methods.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.460-465
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• 2004

In this paper, we present some properties on receding horizon $H_{\infty}$ control for nonlinear discrete-time systems. First, we propose the nonlinear inequality condition on the terminal cost for nonlinear discrete-time systems. Under this condition, noninceasing monotonicity of the saddle point value of the finite horizon dynamic game is shown to be guaranteed. We show that the derived condition on the terminal cost ensures the closed-loop internal stability. The proposed receding horizon $H_{\infty}$ control guarantees the infinite horizon $H_{\infty}$ norm bound of the closed-loop systems. Also, using this cost monotonicity condition, we can guarantee the asymptotic infinite horizon optimality of the receding horizon value function. With the additional condition, the global result and the input-to-state stable property of the receding horizon value function are also given. Finally, we derive the stability margin for the saddle point value based receding horizon controller. The proposed result has a larger stability region than the existing inverse optimality based results.

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.1-6
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• 2008

The tilt rotor aircraft has the flight characteristics which takes off vertically like a helicopter and flies forward like an airplane. Especially, the transition process from a helicopter to an airplane mode requires not only the mixing of control inputs but also the stability and controllability augmentation system(SCAS) in order to keep the safe flight because there are compound flight dynamic characteristics of a helicopter and an airplane including non-linearity, uncertainty. This paper describes the design of SCAS in a lateral motion for the tilt rotor aircraft based on the $H_{\infty}$ control method, which was performed from mathematical model with weighting matrix based on the relationship between the $H_{\infty}$ norm and the sensitivity function. Through simulation analysis for the controller designed on the $H_{\infty}$ control theory, it was shown that this method may be applied to the control design of the tilt rotor aircraft.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.549-551
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• 1998

In this paper, we design the optimal satellite-tracking antenna $H_{\infty}$ control system using genetic algorithm(GA). To do this, we give gain and dynamics parameters to the weighting functions and apply 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 simultaneously optimized in tile search domain guaranteeing the robust stability of closed-loop system. The effectiveness of this satellite-tracking antenna $H_{\infty}$ control system is verified by computer simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.679-687
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• 2013

This paper proposes a new condition about delay-dependent robust $H_{\infty}$ control of uncertain linear systems with time-varying delay and randomly occurring disturbances. The norm bounded uncertainties are subjected to the system matrices. Based on Lyapunov stability theory, a sufficient condition for designing a controller gain such that the closed-loop systems are asymptotically stable with $H_{\infty}$ disturbance level ${\gamma}$ is formulated in terms of linear matrix inequalities (LMIs). Finally, two numerical examples are included to show the effectiveness of the presented method.