• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.196-202
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• 2002

In this work, we propose a new type of HDD suspension featuring shape memory alloy (SMA) actuator in order to prevent the contact between the slider and disk. The principal design parameters are obtained from the modal analysis using finite element analysis, and then the dynamic model is established to formulate the control scheme for Non-Contact Start/stop mode drive. Subsequently, a robust H$\_$$\infty$/ control algorithm is designed by integrating experimentally-Obtained SMA actuator dynamics to the proposed HDD suspension system. The controller is empirically realized and control results for the load/unload profiles are presented in time domain. In addition, the contact signal between the slider and disk is measured by the electrical resistance method.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.142-146
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• 2000

In this paper, we are applied the Genetic Algorithm(GA) to design of the robust $H^{\infty}$ speed controller by auto-tuning of the weighting function. GA is used to design of the weighting functions in the robust $H^{\infty}$ controller. To evaluate the performances of the proposed robust $H^{\infty}$ controller, we make an experiment on $H^{\infty}$ speed controller of an actual DC servo- motor system with nonlinear characteristics. Experimental results show that proposed controller have better performance than those of PD controller.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2191-2193
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• 2004

The Sliding Mode Control is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. So in this paper, a controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.761-763
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• 1999

When the controller designed by the $H{\infty}$ control technique is applied to the object system, sometimes the controller does not satisfy the robust stability and robust performance but only satisfy the nominal performance. In this paper, we derive the region on the frequency response curve of the open-loop transfer function which satisfy the robustness and robust performance of the designed controller. We also derive the region for the suitableness of the weighting function on the frequency response curve of the weighting function. We showed that the robust stability and the robust performance of the $H{\infty}$ optimal control)or by applying the designed controller on an electromechanical actuator system could be improved by determining parameter ${\gamma}$ and weighting function gain ${\alpha}$ using the derived region.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.157-159
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• 1999

This paper presented design of an $H_{\infty}$ controller for TCSC to enhance the damping of an inter-area oscillation in KEPCO power system. TCSC location is selected by using eigne sensitivity and frequency response. Nonliner time simulation and eigenvalue analysis show that the proposed TCSC $H_{\infty}$ controller can suppress the inter-area oscillations efficiently with induced reduction model correctly.

• 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 KIEE Conference
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• 1997.07b
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• pp.679-681
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• 1997

A $H_{\infty}$ adaptive controller is designed by using polynomial approach. The $H_{\infty}$ robust controllers for adaptive system were designed by Grimble. But they did not minimize the mixed sensitivity ra cost function which is the re sum of weighted sensitivity and complementary sensitivity terms Moreover pole placement is dependent of cost function. In this paper, the mixed sensitivity re cost function is minimized by employing the Youla parameterization and polynomial approach at the same time. And pole plaement is independent of weighting function.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.04a
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• pp.149-152
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• 2005

In this paper, a robust $H\infty$ stabilization problem to a uncertain discrete-time fuzzy systems with time-varying delay via static output feedback is investigated. The Takagi -Sugeno (T-S) fuzzy model is employed to represent an uncertain nonlinear systems with time-varying delayed state. Using a single Lyapunov function, the globally asymptotic stability and disturbance attenuation of the closed-loop fuzzy control system are discussed. Sufficient conditions for the existence of robust $H\infty$ controllers are given in terms of linear matrix inequalities.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2642-2644
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• 2000

In this paper, the decoupling $H_{\infty}$ controller which minimizes maximum energy in the output signal is designed to reduce the coupling properties between input/output variables which make it difficult to efficiently control a system. And for a given decoupling $H_{\infty}$ problem, an efficient method is sought to find the controller coefficients through Linear Matrix Inequalities(LMI) by which the problem is formulated into a convex optimal problem.