• Journal of Applied Reliability
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• v.9 no.1
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• pp.13-28
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• 2009

In this paper we propose a method for designing optimum degradation test based on nonlinear random-coefficients models. We use the approximated expression of the Fisher information matrix for nonlinear random-coefficients models. We apply the simplex algorithm to the inverse of the determinant of Fisher information matrix to satisfy the D-optimal criterion. By comparison of the results from PDP degradation data, we suggest a general guideline to obtain optimum experimental design for determining inspection intervals and number of samples in degradation testing.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.156-160
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• 1993

This paper presents a controller design to coordinate a robot manipulator under unknown system parameters and bounded disturbance inputs. To control the motion of the manipulator, an inverse dynamics control scheme is applied. Since parameters of the robot manipulators such as mass and inertia are not perfectly known, the difference between the actual and estimated parameters works as a disturbance force. To identify the unknown parameters, an inproved adaptive control algorithm is directly derived from a chosen Lyapunov's function candidate based on the Lyapunov's Second Method. A robust control algorithm is devised to counteract the bounded disturbance inputs such as contact forces and disturbing force coming from the difference between th actual and the estimated system parameters. Numerical examples are shown using three degree-of-freedom planar arm.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.81-84
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• 1996

We propose the robust nonlinear controller design methodology, the $H_{\infty}$ constrained quasi - linear quadratic Gaussian control (QLQG/ $H_{\infty}$), for the statistically-linearized multivariable system with hard nonlinearties such as Coulomb friction, deadzone, etc. The $H_{\infty}$ performance constraint is involved in the optimization process by replacing the covariance Lyapunov equation with the Riccati equation whose solution leads to an upper bound of the QLQG performance. Because of the system's nonlinearity, however, one equation among three Riccati equations contain the nonlinear correction terms that are very difficult to solve numerically. To treat this problem, we use simple algebraic techniques. With some analytic transformation for Riccati equations, the nonlinear correction terms can be so eliminated that the set of a linear controller to the different operating points are designed. Synthesizing these via inverse random input describing function (IRIDF) technique, the final nonlinear controller can be designed.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.281-284
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• 1998

In this paper, a RS(Reed-Solomon) docoder is designed in the transform domain instead of most time domain. The transform RS decoder have simpler structure for error-correction procedure but because of his larger chip area, the time domain RS decoder is popular currently. To solve this proplem, the nomal basis representation and the conjugate property is utilized. Therefore the chip area can be reduced for the stucture of syndrome delay, nomalization and inverse transform circuit. These modified structures have been implemented using VHDL and synthesized on 0.8${\mu}{\textrm}{m}$ CMOS technology. The results have been compared with other structure for chip area and performance.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.10
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• pp.64-72
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• 1995

In this paper, atmospheric turbulence and absorption under clear weather condition, which affect the optical satellite up-link communication between geo-satellites and earth station, were studied. In case of the up-link communication, the received optical power is weakened by pointing loss caused by beam tilt which is the main effect of turbulent atmosphere. This pointing loss directly has relation to the diameter of optical transmitting antenna. From the inverse proportion of the pointing and spaced loss, it is the regions where the diameter of transmitting antenna increases abruptly and the efficient design of transmitting antenna is impossible. In case of using channel coding, it was shown that the peak value of diameter moved to the lower regions of elevation angle with increasing the coding gain and its width was also decreased. In case of considering both coding gain and transmission rate on the design of transmitting antenna, it was known that more coding gain was necessary as transmission rate was increased.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.185-190
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• 2001

The cavitation causes suction performance and efficiency of the high-speed pump to be reduced significantly To diminish these effects, the inducer has been used. Most of the inducer is designed at a maximum efficiency point of the pump, therefore suction performance drop due to effects of flow separation and inlet inverse flow is often observed at off-design point. The objective of this study is to find out the cavitation modes at various conditions by applying event detection technique and to design an inducer reducing cavitation. The pressure fluctuations at each cavitating condition were measured at inducer inlet and outlet locations using pressure transducers, which were located 90 degrees apart from each other to identify the cavitation modes. The time-frequency characteristics were analyzed by using Choi-williams distribution. In the second part of this paper, the inducer design method which uses nominal performance characteristic and onset condition of cavitation is introduced and applied to real situation.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.304-308
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• 2000

This paper presents a numerical optimization method to design geometric shape of streamwise periodic ribs mounted on one of the principal walls to enhance turbulent heat transfer in a rectangular channel flow. The golden section method is used for the one dimensional search. The optimization is based on Wavier-Stokes analysis of turbulent forced convection with $k-{\varepsilon}$ turbulence model. The width-to-height ratio of a rib is chosen as a design variable. The object function is defined as an inverse of average Nusselt number. An optimum shape of the rib has been obtained with reasonable computing time.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.741-744
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• 1999

In this paper, We represent a low complexity of parallel canonical basis multiplier for GF( q$^{n}$ ), ( q＞ 2). The Mastrovito multiplier is investigated and applied to multiplication in GF(q$^{n}$ ), GF(q$^{n}$ ) is different with GF(2$^{n}$ ), when MVL is applied to finite field. If q is larger than 2, inverse should be considered. Optimized irreducible polynomial can reduce number of operation. In this paper we describe a method for choosing optimized irreducible polynomial and modularizing recursive polynomial operation. A optimized irreducible polynomial is provided which perform modulo reduction with low complexity. As a result, multiplier for fields GF(q$^{n}$ ) with low gate counts. and low delays are constructed. The architectures are highly modular and thus well suited for VLSI implementation.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1509-1510
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• 2008

In this paper, we propose a robust adaptive controller for induction motors with uncertainties using nonlinear disturbance observer(NDO). The proposed NDO is applied to estimate the time varying lumped uncertainty which are derived from unknown motor parameters and load torque, but NDO error does not converge to zero since the derivate of lumped uncertainty is not zero. Then the high order neural networks(HONN) is presented to estimate the NDO error such that the rotor speed to converge to a small neighborhood of the desired trajectory. Rotor flux and inverse time constant are estimated by the sliding mode adaptive flux observer. Simulation results are provided to verify the effectiveness of the proposed approach.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.121-126
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• 1999

In this paper, to bring under robust and accurate control of auto-equipment systems which disturbance, parameter alteration of system, uncertainty and so forth exist, neural network controller called dynamic neural processor(DNP) is designed. In order to perform a elaborate task like as assembly, manufacturing and so forth of components, tracking control on the trajectory of power coming in contact with a target as well as tracking control on the movement course trajectory of end-effector is indispensable. Also, the learning architecture to compute inverse kinematic coordinates transformations in the manipulator of auto-equipment systems is developed and the example that DNP can be used is explained. The architecture and learning algorithm of the proposed dynamic neural network, the DNP, are described and computer simulations are provided to demonstrate the effectiveness of the proposed learning method using the DNP.