• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.449-451
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• 1998

In this paper, we consider the problem of the robust stability of uncertain linear systems with multiple time-varying delays. The considered uncertainties are both the unstructured uncertainty which is only known its norm bound and the structured uncertainty satisfying the matching conditions, respectively. We present conditions that guarantee the robust stability of systems based on Lyapunov stability theorem and $H_{\infty}$ theory in the time domain. Finally, we show the usefulness of our results by numerical examples.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.463-465
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• 1998

In this paper, we consider the problem of robust stability of large-scale uncertain linear systems with time-varying delays. The considered uncertainties are both unstructured uncertainty which is only known its norm bound and structured uncertainty which is known its structure. Based on Lyapunov stability theorem and $H_{\infty}$ theory. we present uncertainty upper bound that guarantee the robust stability of systems. Especially, robustness bound are obtained directly without solving the Lyapunov equation. Finally, we show the usefulness of our results by numerical example.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.92-99
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• 2001

This paper presents a simulation study using a robust controller to improve the roll stability of a vehicle. The controller is designed in the framework of an output feedback H$_{\infty}$ control scheme based on the 3DOF linear vehicle model, solving the mixed-sensitivity problem to guarantee the robust stability and disturbance rejection with respect to parameter variations due to laden and running vehicle conditions. In order to investigate the feasibility of the active roll control system in a real car, its performance is evaluated by simulation in a 10DOF full vehicle model with actuator dynamics and tire characteristics.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.2
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• pp.93-102
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• 2005

The Nyquist robust stability margin is proposed as a measure of robust stability for systems with Affine TFM(Transfer Function Matrix) parametric uncertainty. The parametric uncertainty is modeled through a Affine TFM MIMO (Multi-Input Multi-Output) description with dead-time, and the unstructured uncertainty through a bounded perturbation of Affine polynomials. Gershgorin's theorem and concepts of diagonal dominance and GB(Gershgorin Bands) are extended to include model uncertainty. Multiloop PI/PID controllers can be tuned by using a modified version of the Ziegler-Nichols (ZN) relations. Consequently, this paper provides sufficient conditions for the robustness of Affine TFM MIMO uncertain systems with dead-time based on Rosenbrock's DNA. Simulation examples show the performance and efficiency of the proposed multiloop design method for Affine uncertain systems with dead-time.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.81-87
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• 1993

In this paper robust stability conditions are obtained for linear dynamical systems under structured nonlinear time-varying perturbations, using absolute stability theory and the concept of dissipative systems. The conditions are expressed in terms of solutions to linear matrix inequality(LMI). Based on this result, a synthesis methodology is developed for robust feedback controllers with worst-case H$_{2}$ perforrmance via convex optimization and LMI formulation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.6
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• pp.437-443
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• 1987

Due to the recent development of microprocessor, the digital control is now in use for the practical structure of the control systems, but it leaves the problem of controlling delays caused by computation time when it is applied to the realization problems, such as application method of the control law and controlling effect of continuous control, etc. This paper deals with robust stability of the digital regulator which compensates for the controlling delays by applying prediction values of state.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.139-144
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• 1993

In this paper, a robust reduced order adaptive controller is proposed based on Internal Model Control(IMC) structure for stochastic linear stable systems. The concept of gain margin is utilized to make the adaptive IMC controller robust. We prove the stability of the proposed adaptive IMC system for stable plants under the assumption that upper bounds for system orders are known. Simulation results show that the proposed method has good performance and stability robustness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.401-405
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• 1996

A new method of nonlinear robust controller synthesis is introduced which is an extension of linear mixed $H_2/H_{\infty}$ control. This method guarantees robust stability fur hard nonlinearity and uncertainty of the plant. The method is applied to the control of a flexible link of robot with Coulomb friction. Simulation shows good performances with respect to the response and the robustness.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.05a
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• pp.4-7
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• 2001

A stable TSK-type FLC can be designed by the method of Parallel Distributed Compensation (PDC), but in this case, solving the LMI problem is not a trivial task. To overcome such a difficulty, a Time-Delay based FLC (TDFLC) is proposed. TSK-type TDFLC consists of Time-Delay Control (TDC) and Sliding Mode Control (SMC) schemes, which result in a robust controller basaed upon an integral sliding surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1833-1844
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• 2004

A controller is proposed for the robust backstepping control of a class of nonlinear multiple-input multiple-output (MIMO) systems which can be converted to a strict feedback form. The proposed robust backstepping control scheme follows a systematic procedure for the design of control laws and uses time delay estimation (TDE) to estimate the uncertainties such as parameter variations, unknown disturbances, and unmodeled dynamics, etc. The proposed controller can be also applied to nonlinear MIMO systems with unmatched uncertainties. Stability analysis of the closed-loop system which contains the plant and the proposed controller is also studied and hereby a sufficient stability condition for the closed-loop system is proposed. The simulation results show that the control scheme works well with uncertainties and the proposed stability condition is valid. The controller is experimentally verified on a single-link flexible arm to show the effectiveness of the proposed scheme in the complicated systems with uncertainties.