• Journal of the Korean Data and Information Science Society
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• v.12 no.2
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• pp.125-143
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• 2001

We, in this paper, propose a kernel estimator of hazard ratio with censored survival data. The uniform consistency and asymptotic normality of the proposed estimator are proved by using counting process approach. In order to assess the performance of the proposed estimator, we compare the kernel estimator with Cox estimator and the generalized rank estimators of hazard ratio in terms of MSE by Monte Carlo simulation. Two examples are illustrated for our results.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.598-600
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• 1998

In this paper, a robust controller is proposed to achieve the accurate tracking for uncertain robot manipulators with hydraulic actuator dynamics. The parameter uncertainty can be quantified by the linear parameterization technique. A switching controller is proposed to guarantee the global asymptotic stability of the plant. In order to eliminate the chattering caused by the switching controller, a smoothing controller is proposed using the boundary layer technique around the sliding surface. It is shown that the smoothing controller guarantees the uniform ultimate boundedness of the tracking, error. The proposed controller shows good better tracking performance.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.84-91
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• 2000

This paper describes a state feedback controller design method of the integral type magnetic levitation servo system which satisfies the design objectives. The design objective is a $H_{\infty}$ performance, asymptotic disturbance rejection and a robust pole assignment in linear matrix inequality(LMI) region. To the end, we investigated the validity of the designed controller which considering a robust pole assignment region, through results of simulation.

• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.475-484
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• 2004

In this paper, we present a dynamic output-feedback receding horizon $H_{\infty}$controller for linear discrete-time systems with disturbance. The controller is obtained numerically from the finite horizon output-feedback $H_{\infty}$optimization problem, which is, in fact, hardly solved analytically. Under a matrix inequality condition on the terminal weighting matrix, the monotonic decreasing property of the cost is shown. This property guarantees both the closed-loop stability and the $H_{\infty}$norm bound. Then, we extend the proposed design method to a reference tracking problem and a problem for time-varying systems. Numerical examples are given to illustrate the performance of the proposed controller.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.265-270
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• 2001

In this paper, a robust controller is proposed to control a robot manipulator which is governed by highly nonlinear dynamic equations. The controller is computationally efficient since it does not require the dynamic model or parameter values of a robot manipulator. It, however, requires uncertainty bounds which are derived by using properties of revolute joint robot dynamics. The stability of the robot with the controller is proved by using Lyapunov's direct method. The results of computer simulations also show that the robot system is stable, and has excellent trajectory tracking performance.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.3
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• pp.394-401
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• 2010

In this article, we investigate a robust friction compensation scheme for the purpose of accomplishing precision positioning performance a servo mechanical system with nonlinear dynamic friction. To estimate the friction state and tackle robustness problem for uncertainty, a RFNN and reconstructed error compensator as well as a robust friction state observer are developed. The asymptotic stability of the series of friction compensation methodologies are verified from the Lyapunov's stability theory. Some simulations and experiments on a servo mechanical system were carried out to evaluate the effectiveness of the proposed control scheme.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.949-955
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• 1997

Detection of the existence of a desired user is considered in this paper. We assume that the signal to noise ratio is high enough for us to ignore the effects of noise compared with those of the interference by other users. The inter-user interference and user signals are modeled by the Nakagami model. An observation model for this situation is proposed, the locally optimum test statistic is derived under the model, and the asymptotic performance of the locally optimum detector is compared with of the envelope detector. We show that the locally optimum detector performs better than the conventional envelope detector.

• Journal of the Korean Data and Information Science Society
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• v.23 no.3
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• pp.579-585
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• 2012

Many different semi-supervised learning algorithms have been proposed for use wit unlabeled data. However, most of them focus on classification problems. In this paper we propose a semi-supervised regression algorithm called the semi-supervised local constant estimator (SSLCE), based on the local constant estimator (LCE), and reveal the asymptotic properties of SSLCE. We also show that the SSLCE has a faster convergence rate than that of the LCE when a well chosen weighting factor is employed. Our experiment with synthetic data shows that the SSLCE can improve performance with unlabeled data, and we recommend its use with the proper size of unlabeled data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.166-174
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• 1996

In this paper, a new modified independent modal space control(IMSC), which relaxes the fundamental hardware limitation of IMSC, is suggested to handle the vibration and attitude control problem for flexible large structures. This method has adapted a new switching algorithm between controlled modes and a novel design technique for modal control force. The main advantage of this method is to minimize the discontinuity of the modal control forces and to assure the asymptotic stability of the closed-loop systems. This process is shown to be simple and efficient in a realistic example of vibration control of a cantilever beam. It has been found that the modified IMSC suggested in this paper, which can reduce the number of actuators, is highly excellent compared to other previous methods in terms of the performance and stability of the vibration control systems.