• Structural Engineering and Mechanics
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• v.76 no.1
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• pp.101-114
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• 2020

In this paper, an improved experience-based learning algorithm (EBL), termed as IEBL, is proposed to solve the nonlinear hysteretic parameter identification problem with Bouc-Wen model. A quasi-opposition-based learning mechanism and new updating equations are introduced to improve both the exploration and exploitation abilities of the algorithm. Numerical studies on a single-degree-of-freedom system without/with viscous damping are conducted to investigate the efficiency and robustness of the proposed algorithm. A laboratory test of seven lead-filled steel tube dampers is presented and their hysteretic parameters are also successfully identified with normalized mean square error values less than 2.97%. Both numerical and laboratory results confirm that, in comparison with EBL, CMFOA, SSA, and Jaya, the IEBL is superior in nonlinear hysteretic parameter identification in terms of convergence and accuracy even under measurement noise.

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1846-1855
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• 2005

This paper presents a new stochastic controller applied on the vibration control system under irregular disturbances based on the mode selection scheme. Measured displacement and frequency characteristics are simultaneously used in designing a mode selecting controller. This technique is validated by applying to the suppression problem of a flexible beam with randomly vibrated circumstances. The presented method, called Mode Selecting Stochastic Controller, uses the frequency measurement of the flexible system based on a Fast-Fourier transformation algorithm. This controller is constructed by combining mode selection method with previous known Stochastic Controller in real time: Numerical simulations and several experiments are conducted to validate the proposed method. The performance of the proposed method is compared with a stochastic controller developed recently. This method was improved compared with previous one.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.3
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• pp.104-110
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• 2006

It is a study on the design of a cam profile for diesel engine SOHC. It is used a reverse engineering method without the usual copy processing. It draws up the contour data from an actual cam and processes by CNC. The profile of the cam is reappeared to be up to operational specifications that are the opening and shutting time, lift, speed and acceleration of the inhalation and escape valves. While the cam operating, the noise and vibration are occurred by the sudden change of speed. The new design of cam profile is suitable fur the valve operations to be smooth. We propose the design method of a cam profile far the reappearance of an actual cam. It is proved to be the propriety about the design of the cam profile through the processing, measurement, and comparison of the cam profile.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.818-823
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• 2003

본 논문에서는 입력 매칭(input matching) BIST(Built-In Self-Test) 회로를 이용한 RF font end의 새로운 결함 검사방법을 제안한다. BIST 회로를 가진 RF front end는 1.8GHz LNA(Low Noise Amplifier: 저 잡음 증폭기)와 이중 대칭 구조의 Gilbert 셀 믹서로 구성되어 있으며, TSMC 0.25$\mu\textrm{m}$ CMOS 기술을 이용하여 설계되었다. catastrophic 결함 및 parametric 변동을 가진 RF front end와 결함을 갖지 않은 RF front end를 판별하기 위해 RF front end의 입력 전압 특성을 조사하였다. 본 방법에서는 DUT(Device Under Test: 검사대상이 되는 소자)와 BIST 회로가 동일한 칩 상에 설계되어 있기 때문에 측정할 때 단지 디지털 전자계와 고주파 전압 발생기만이 필요하며, 측정이 간단하고 비용이 저렴하다는 장점이 있다. BIST 회로가 차지하는 면적은 RF front end가 차지하는 전체면적의 약 10%에 불과하다. 본 논문에서 제안하는 검사기술을 이용하여 시뮬레이션해 본 결과 catastrophic 결함에 대해서는 100%, parametric 변동에 대해서는 약 79%의 결함을 검출할 수 있었다.

• Journal of Navigation and Port Research
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• v.30 no.2
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• pp.119-124
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• 2006

In Part I(theoretical study) of the paper, a new adaptive autopilot for ships based on Adaptive Neural Networks was proposed. The ANNAI autopilot was designed for course-keeping, turning and track-keeping control for ships. In this part of the paper, to show the effectiveness and feasibility of the ANNAI autopilot and automatic selection algorithm for learning rate and number of iterations, computer simulations of course-keeping and track-keeping tasks with and without the effects of measurement noise and external disturbances are presented. Additionally, the results of the previous studies using Adaptive Neural Network by backpropagation algorithm are also showed for comparison.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.42-51
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• 2000

The performances of the simple expansion, perforated tube, and conical-connector type as an exhaust muffler are shown in this study. Applying a model in which the method of four-pole parameter is used makes theoretical estimation of the insertion loss. Experiment is performed for the measurement of the insertion loss under four cases according to the variation of the tail pipe length. By comparing the theoretical prediction with the experimental results, the validity of the modeling using the method of four-pole parameter is verified. The personal computer simulation programs for the above mentioned theory on the muffler design have been developed and exhaust sound level measurements have been carried out for simple expansion muffler, conical-connector muffler, perforated tube mufflers and the combined type of conical-connector and simple expansion muffler. The measured results for attenuation characteristics of noise for each muffler are compared with the computed theoretical results to verity the confidence and applicable limits of the theoretical equation derived.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.1
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• pp.63-71
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• 1987

The measuring of acoustic intensity has been investigated by many researchers and practicians during the last several decades. But due to the lack of measurement accuracy, they have had no practical use. In recent years, the two microphone acoustic intensity method has been developed by the advancement of FFT analysis technique and the digital data processing equipment. This new method of using two microphones gives informations on the noise source survey and the acoustic power of sound radiation source without the anechoic room. In this paper, theoretical formulae for the two microphone acoustic intensity method and the sound transmission loss are checked. The obtained results for the acoustical enclosure of gas heat pump were compared with the classical field incidence mass law. The surface vibration modes for a panel of enclosure were also estimated.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.693-698
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• 2000

Aspects of classical information theory, such as rate distortion theory, investigate how to encode and decode information from an independently identically distributed source so that the asymptotic distortion rate between the source and its quantized representation is minimized. However, in most natural dynamics, the source state is highly corrupted by disturbances, and the measurement contains the noise. In recent coder-estimator sequence is developed for state estimation problem based on observations transmitted with finite communication capacity constraints. Unlike classical estimation problems where the observation is a continuous process corrupted by additive noises, the condition is that the observations must be coded and transmitted over a digital communication channel with finite capacity. However, coder-estimator sequence does not provide such a quantitative analysis as a variance for estimation error. In this paper, under the assumption that the estimation error is Gaussian distribution, a variance for coder-estimation sequence is proposed and its fitness is evaluated through simulations with a simple example.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.623-628
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• 2000

Since the influence coefficients method in balancing of rotors is developed with the basement of not the principle of rotor system dynamics, but the linear relationshop of between the measuring quantities and the unbalance quantities, field engineers can apply the method without additional understanding on the rotor dynamics. But the influence coefficients method is not robust to the measurement error. This paper proposes a new method for the two plane balancing of rigid rotor, based on the principle of rotor dynamics. And the kit for experiment is made by ourselves, and in order to measure in the same condition with it, we do a experiment three times. And then with the Response of gap sensor, the SNR(Signal and Noise) is compared and analyzed about measuring error between the influence coefficient method, and the new method, and it is proved that the new method is less robust than the influence coefficient method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.609-612
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• 2001

Rogowski coil is made having no ferromagnetic material in a core. So the coil cannot be driven into saturation. This result in that Rogowski coils may be calibrated at relatively low currents. and used with confidence at very high currents. However the lowest level of current that can be measured is limited by the sensitivity of the voltage measuring instrument and system noise. Therefore. geometrical effects were investigated in order to measure high sensitivity of low level current and the significant source of error was examined as well. In the results, the source of error was associated with coil designs. i.e. shape and uniformity of coil and a geometrical location of current source inside and outside of the Rogowski coil.