• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.956-960
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• 1987

This paper investigates the control problem which is specified by an uncertain linear system and a linear quadratic performance index. Only the size of parameter uncertainty is assumed to be given instead of its statistics. In addition, a mathing condition which constrains the system structure is assumed to be satisfied. The control law can be obtained by solving an LQ optimal control problem for a nominal system.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1898-1913
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• 2006

This paper deals with the design of a yaw rate controller based on gain-scheduled H$\infty$ optimal control, which is intended to maintain the lateral stability of a vehicle. Uncertain factors such as vehicle mass and cornering stiffness in the vehicle yaw rate dynamics naturally call for the robustness of the feedback controller and thus H$\infty$ optimization technique is applied to synthesize a controller with guaranteed robust stability and performance against the model uncertainty. In the implementation stage, the feed-forward yaw moment by driver's steer input is estimated by the disturbance observer in order to determine the accurate compensatory moment. Finally, HILS results indicate that the proposed yaw rate controller can satisfactorily improve the lateral stability of an automobile.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.384-394
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• 2002

In this paper, a new control strategy is proposed to improve the quality of the welding products. The conventional nonlinear power control system of spot welders is linearized using nonlinear feedback linearization technique based on differential geometry theory. An evolution strategy(ES) geometry is used to find optimal gain of PI controllers. It tries to find out the optimal control parameters by imitating the natural evolution. Some Simulation and experimental results show that the proposed variable power control system using ES algorithm has better dynamic performances than the conventional one.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.324-328
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• 2007

An analytical framework for fuzzy modeling and control of nonlinear systems using a set of linear models is presented. Fuzzy clustering is applied on the aerodynamic coefficients of a missile to obtain an optimal number of rules in a Tagaki-Sugeno fuzzy rule-set. Next, the obtained membership functions and rule-sets are applied to a set of linear optimal controllers towards extraction of a global controller. Reported simulations demonstrate the performance, stability, and robustness of the controller.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.338-341
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• 1994

This paper presents a Fuzzy-PID controller based on Fuzzy logic. Up to now PID controller has had the difficulty of obtaining the optimal gain, and Fuzzy controller has had the difficulty of determining scale factor affecting the performance of control. So that a Fuzzy-PID controller is presented here self tuning of the scale factor and optimal gain. The results of simulation show a good performance in comparison with Ziegler-Nichols controller, having the generality of determining the components of scale factor in Fuzzy rule.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1408-1410
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• 2000

The regulation performances needs high control gain in novel output feedback controller but high control gain is decreased relative stability of the total system. Thus, this paper proposed neural network controller(NNC) for output feedback controller. In this scheme, output feedback controller are guarantee global stability and NNC are controller steady-state error and defined optimal control law. And we demonstrated this scheme by simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.231-232
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• 2007

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.467-472
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• 1989

In this study, a design method to obtain a robust optimal regulator for linear multivariable system is presented. When assigning eigenvalues of linear multivatiable system , the feedback gain is not unique. So we can assign robustness index to optimality so that we can fully use the remained degree of freedom.

• Proceedings of the KIEE Conference
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• 1981.07a
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• pp.146-153
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• 1981

A practical and robust control scheme is suggested for MIMO discrete time processes with real simple poles. This type of control scheme, having the advantages of both the adaptiveness and optimality, may be successfully applicable to structured dynamic controllers for plants whose parameters are slowly time-varying. The identification of the process parameters is under-taken in ARMA form and the optimization of the feedback gain matrix is performed in the state space representation with regard to a standard quadratic criterion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1665-1676
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• 2001

The effect of spreading gain control on the throughput of a CDMA slotted ALOHA system is considered. Mobile users transmit packets over a shared channel, and the packets transmitted in the same time slot over the shared channel act as simultaneous access interference (SAI). When using spread-spectrum signal, a CDMA slotted ALOHA channel achieves high probability of capture due to the property of high title resolution, and the bit rate of user information is determined by spreading gain. When the SAI level gets larger, the high value of spreading gain enhances the packet throughput by increasing the probability of a successful packet transmission, while it degrades the of the effective throughput by reducing the user information bits carried within a packer. To solve the problem, we investigated the effect of the capture probability and the SAI level on these system throughputs, and evaluated the throughput performance of the system for each spreading gain control scheme. The results showed that the maximum effective throughput could be achieved with an unified method despite the variation of the SAI level by deriving an optimal value of the spreading gain according to 171e system states.