• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.367-369
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• 1986

Guaranteed cost control is a method applicable to a class of systems with uncertain parameters that guarantees an upper bound of the cost functional. This paper is concerned with a matrix decomposition technique used to yield a reasonable upper bound of the cost functional for a finite-time LQ regulator problem. The uncertain linear systems dealt with in this paper are described by a set of state equations of single-input phase-variable canonical form which contain unknown but bounded uncertain parameters.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 춘계학술대회 논문집
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• pp.46-58
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• 1991

An upper-bound method is applied to determine the final-stage extrsuion load and the deformed configuration of extruded billet. A simple kinematically admissible velocity field for trhee-dimensional deformation at final-stage is proposed. From the proposed velocity field the upper-bound extrusion load, the velocity distribution and the configuration of extruded billet are determined byminimizing the otoal power consumption. Experiments are carried out with full-annealed commercial aluminum billets at room temperature by using different sizes of elliptic punches. The theroretical predictions both in extrusion load and deformed configuration of extruded billet are ingood agreements with the experimentalresults.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권1호
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• pp.168-186
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• 2016

In this paper, we investigate the degrees of freedom (DoF) of a two-cluster multiple-input multiple-output (MIMO) multiway relay interference channel (mRIC), where there are two relays and two users per cluster. In this channel, users within the same cluster exchange messages among themselves with the help of two relays.We first obtain the DoF upper bound of the considered MIMO mRIC based on cut-set bound. Then, we propose a novel transmission strategy, blind interference neutralization (BIN), to approach the DoF upper bound. This new method utilizes the overheard information at two relays and focuses on the beamforming matrix designs at two relays so that the channel state information (CSI) at users is not required. Through theoretical analysis and numerical simulations, we show that the DoF upper bound can be obtained by using the BIN scheme. From simulation results, we show that the proposed BIN scheme can provide significant performance gain over the conventional time division multiple access (TDMA) scheme in terms of DoF. In addition, we show that the BIN scheme is a superior approach to the existing signal space alignment (SSA) schemes for the considered mRIC.

• 소성∙가공
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• 제3권1호
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• pp.97-109
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• 1994

Closed-die forging of the spur gears with circular are fillet has been analyses by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, the tooth profile consists of the involute curve and the circular arc fillet. In the analysis, the deformation regions have been divided into eight zones. A constant frictional stress has been assumed on the contacting surfaces Utilizing the formulated velocity field, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, addendum modification coefficient and friction factor, on the relative forging pressure of spur gears. As the result of numerical calculations, the relative forging pressure does not change so much against the variation of module. On the other hand, the relative forging pressure increases at the final filling stage as the addendum modification coefficient increases.

• 소성∙가공
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• 제4권3호
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• pp.257-266
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• 1995

A simulation method based on upper bound method is developed in order to characterize forging characters in forging of spur gears. In this paper, utilizing a kinematically admissible velocity field and applying it to investigate the effect of inner diameter of holow billet. In the analysis, to predict the variation of inner diameter of hollw billet, neutral surface has been introduced. The neutral surface of each step is assumed as a circle and determined in order to have minimum forging energy by golden section method. By this method, the variation of inner diameter of billet during spur gear forging is successfully predicted. As a result, the selection of inner diameter of initial billet is very important to reduce the forging load.

• 한국기계가공학회지
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• 제18권9호
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• pp.100-105
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• 2019

In wire drawing, aterial deformation is concentrated on the surface of the drawn wire because of surface contact with the drawing die. Therefore, strain varies from the center to the surface of the drawn wire. In this study, based on the upper bound method, an effective strain prediction method from the center to the surface of a drawn wire was proposed. Using the proposed method, the effective strain of the drawn wire was calculated verify the proposed prediction method, the predicted effective strain was compared with the result of finite element analysis.

• 대한수학회보
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• 제60권5호
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• pp.1181-1199
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• 2023

For solving complex symmetric positive definite linear systems, we propose a single step real-valued (SSR) iterative method, which does not involve the complex arithmetic. The upper bound on the spectral radius of the iteration matrix of the SSR method is given and its convergence properties are analyzed. In addition, the quasi-optimal parameter which minimizes the upper bound for the spectral radius of the proposed method is computed. Finally, numerical experiments are given to demonstrate the effectiveness and robustness of the propose methods.

• 한국정밀공학회지
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• 제14권8호
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• pp.92-100
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• 1997

An upper-bound elemental technique (UBET) analysis is carried out to improve the material flow and to reduce the load of bearing-race forming process. The UBET analysis, which adapts the advantages of stream function and finite element method, is useful for predicting the profile of complex geometric bound- ary. From the UBET analysis, the forming load, the velocity distribution and the stream line of the deformed billet are determined by minimizing the total power consumption with respect to chosen parameters. The results of present UBET analysis are better than those of previous UBET analysis. Experiments have been carried out with model material plasticine billets at room temperature. The theoretical predictions for forming load and flow pattern(stream line) are in good agreement with the experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.62.4-62
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• 2001

In this paper, we propose a delay-dependent guaranteed cost controller design method for uncertain linear systems with time delay. The uncertainty is norm bounded and time-varying. A quadratic cost function is considered as the performance measure for the given system. Based on the Lyapunov method, sufficient condition, which guarantees that the closed-loop system is asymptotically stable and the upper bound value of the closed-loop cost function is not more than a specied one, is derived in terms of Linear Matrix Inequalities(LMIs) that can be solved sufficiently. A convex optimization problem can be formulated to design a guaranteed cost controller, which minimizes the upper bound value of the cost function. Numerical examples show the activeness of the proposed method.

• 한국정밀공학회지
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• 제14권6호
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• pp.142-148
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• 1997

In this paper, forging of internal triangular and involute serrations are analyzed by upper bound method. Kinematically admissible velocity fields for half pitch of the serration were proposed. It was assumed that the shape flow surface during forging is a straight line perpendicular to plane of symmetry. Using the suggested velocity fields, forging loads and relative pressures were calculated by numerical method. Experiments were carride out with commercial AI 2024 aluminium alloy. As a result, the calculated solutions are good agreement with experimental results, so it is useful to predict the loads for forging of internal serrations.