• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.1-14
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• 2008

This paper presents a convex optimization method for observer-based mixed $H_2/H_{\infty}$ control design of linear systems with time-varying state, input and output delays. Delay-dependent sufficient conditions for the design of a desired observer-based control are given in terms of linear matrix inequalities (LMIs). An observer-based controller which guarantees asymptotic stability and a mixed $H_2/H_{\infty}$ performance for the closed-loop system of the linear system with time-varying delays is then developed. A Lyapunov-Krasovskii method underlies the observer-based mixed $H_2/H_{\infty}$ control design. A numerical example with simulation results illustrates the effectiveness of the methodology.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1159-1161
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• 1997

This paper presents a power system stabilizer(PSS) using the $H_{\infty}$ observer-based sliding mode controller($H_{\infty}$ observer-based SMC) for unmeasurable state variables. The effectiveness of the proposed $H_{\infty}$ observer-based SMPSS for unmeasurable state variables is shown by the simulation result.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.130-140
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• 2003

This paper presents an $H_\infty$controller synthesis based on disturbance observer for the trajectory control of a hydraulic excavator. Compared to conventional robot manipulators driven by electrical motors, hydraulic excavator have more nonlinear and coupled dynamics. In particular, the interactions between an excavation tool and the materials being excavated are unstructured and complex. In addition, its operating modes depend on working conditions, which make it difficult to not only derive the exact mathematical model but also design a controller systematically. In this study, the approximated linear model obtained through off-line system identification is used as nominal plant model for a disturbance observer. A disturbance observer based tracking controller which considers the effect of disturbance and model uncertainty is synthesized in $H_\infty$frameworks. Simulation results are used to demonstrate the applicability of the proposed control scheme.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.7-9
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• 2004

This paper provides an observer-based $H_{\infty}$ controller design method for singular systems with and without time-varying delay by just one LMI condition. The sufficient condition for the existence of controller and the controller design method are presented by perfect LMI (linear matrix inequality) approach. The design procedure involves solving an LMI. The observer-based $H_{\infty}$ controller in the existing results can be constructed from the coupled two or more conditions while the proposed controller design method can be obtained from an LMI condition, which can be solved efficiently by convex optimization. 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. An example is given to illustrate the results.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.27-27
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• 2000

The nonlinear observers are proposed for a nonlinear system. To improve the characteristics such as a stability, a convergence, and an H$\sub$$\infty$/ filter performance criterion, we utilize and H$\sub$$\infty$/ filter Riccati equation or a modified H$\sub$$\infty$/ filter Riccati equation with a freedom parameter. Using the Lyapunov, the characteristics of the observer are analyzed. Then the in-flight alignment for a strapdown inertial navigation system(SDINS) is designed using the observer proposed. Simulation results show that the observer with the modified H$\sub$$\infty$/ fitter Riccati equation effectively improve the performance of the in-flight alignment.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2489-2492
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• 2003

In this paper, observer-based H$\sub$$\infty$/ controller design method for singular systems with time-varying delay by Just one LMI condition is presented. The sufficient condition for the existence of controller and the controller design method are presented by one perfect LMI approach. The design procedure involves solving an LMI. 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.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1843-1846
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• 2004

This paper considers a robust observer-based $H_{\infty}$ controller design method for descriptor systems with parameter uncertainties using just one LMI condition. The sufficient condition for the existence of controller and the controller design method are presented by a perfect LMI condition in terms of all variables using singular value decomposition, Schur complement, and change of variables. Therefore, one of the main advantages is that a robust observer-based $H_{\infty}$ controller is found by solving one LMI condition compared with existing results. Numerical example is given to illustrate the effectiveness of the proposed controller design method.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1967-1969
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• 2001

This paper deals with the design of observer-based $H_{\infty}$ controller for linear time-delay systems. By adapting the model transformation and Lyapunov theorem, we presents a sufficient condition which meets the prescribed $H_{\infty}$ norm upper bound from the exogenous disturbances to the measured outputs. The conditions are expressed in terms of coupled two matrix inequalities, and the $H_{\infty}$ controller and the observer are obtained by checking the feasibility of two matrix inequalities. Finally, we shows the usefulness of our result by an example.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.8
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• pp.703-710
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• 2001

The nonlinear observers are proposed for a nonlinear system. To improve the characteristics such as stability, convergence, and $H^{\infty}$ filter performance criterion, we utilize an $H^{\infty}$ filter Riccati equation or a modified $H^{\infty}$ filter Riccati equation with a freedom parameter. Using the Lyapunov function method, the characteristics of the observers are analyzed. Then the in-flight alignment for a strapdown inertial navigation system(SDINS) is designed using the proposed observer. And the additive quaternion error model is especially used to reduce the uncertainty of the SDINS error model. Simulation results show that the observer with the modified $H^{\infty}$ filter Riccati equation effectively improves the performance of the in-flight alignment.