• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.643-648
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• 2003

The problem considered in this paper is that the tip position of a flexible cantilever beam is controlled to follow a command signal, using a pair of piezoelectric actuators at the clamped end. The beam is lightly damped and so the natural transient response is rather long, and also since the sensor and actuator are not collocated, the plant response is non-minimum phase. Two control strategies were investigated. The first involved conventional PID control in which the feedback gains were adjusted to give the fastest closed-loop response to a step input. The second control strategy was based on an internal model control (IMC) architecture. The control filter in the IMC controller was a digital FIR device designed to minimize the expectation of the mean square tracking error. The IMC controller designed fur the beam was found to have very much reduced settling times to a step input compared with those of the PID controller.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.945-954
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• 2004

Recently, specifications of flat display module is going to be higher definition, brightness and more wide viewing angle. On the other hand, physical thickness of those modules is forced to be slimmer and lighter. The flat display modules such as plasma or TFT-LCD employ thin crystallized panels that are normally weak to high level transient mechanical energy inputs. As a result, anti-shock performance is one of the most important design specifications of TFT-LCD modules. TFT-LCD module manufacturers and their customers like PC or TV makers perform a series of strict impact/drop test for the modules. However most of the large display module designs are generated based on engineer's own trial-error experiences. Those designs may result in disqualification from the drop/impact test during final product evaluation. A rigorous study on the impact failure of the displays is of course necessitated in order to avoid the problems. In this article, a systematic design evaluation is presented with combinations of FEM modeling and testing to support the optimal shock proof display design procedure.

• 한국소음진동공학회논문집
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• 제15권5호
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• pp.604-611
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• 2005

The relationship between floor impact sound and vibration has been studied by field measurements, and the vibration modal characteristics have been analyzed. Vibration levels impacted by a standard heavy-weight impact source have been predicted according to the main design parameters using finite element method. Experimental results show that the dominant frequencies of the heavy impact sounds range below 100 Hz and that they are coincident with natural frequencies of the concrete slab. In addition, simple 2-dimensional finite element models are proposed to substitute 2 types of 3-dimensional models of complicated floor structural slabs those by The analytical result shows that the natural frequencies from first to fifth mode well correspond to those by experiments with an error of less than $12\%$, and acceleration peak value iscoincident with an error of less than $2\%$. Using the finite element model. vibration levels areestimated according to the design Parameters, slab thickness, compressive strength, and as a result, the thickness is revealed as effective to increase natural frequencies by $20\~30\%$ and to reduce the vibration level by 3$\~$4 dB per 30 mm of extra thickness.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.702-708
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF). However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the errors. This paper makes clear the relation between the errors of FRF and the length of recording time. A new method is suggested to reduce the errors of FRF in this paper. Several numerical examples for 1-dof model are carried out to show the property of the errors and the validity of the proposed method.

• 한국소음진동공학회논문집
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• 제25권8호
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• pp.553-558
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• 2015

This paper aims at making a dedicated vibration monitoring and diagnosis framework for 3MW WTG(wind turbine generator). Within the scope of the research, vibration data of WTG drive train are used and WTG operating conditions are involved for dividing the vibration data class which included transient and steady state vibration signals. We separate two health detections which are CHD(continuous health detection) and EHD(event health detection). CHD has function of early detection and continuous monitoring. EHD makes the use of finding vibration values of fault components effectively by spectrum matrix subsystem. We proposed framework and showed application for 3MW WTG in a practical point of view.

• 융합보안논문지
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• 제14권5호
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• pp.17-24
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• 2014

본 논문에서는 얼굴 표정 인식을 위한 지역미세패턴(local micro pattern)의 하나인 LBP(Local Binary Pattern) 코드의 잡음에 대한 단점을 해결하기위하여 새로운 미세패턴 방법인 LDP(Local Directional Pattern)를 제안한다. 제안된 방법은 LBP의 문제점을 해결하기 위해 $m{\times}m$ 마스크를 이용하여 8개의 방향 성분을 구하고, 이를 크기에 따라서 정렬한 후 상위 k개를 선정하여 해당 방향을 나타내는 비트를 1로 설정한다. 그리고 8개의 방향 비트를 순차적으로 연결하여 최종 패턴 코드를 생성한다. 실험결과, 제안된 방법은 기존 방법에 비해 회전에 대한 영향이 적으며, 잡음에 대한 적응력이 현저히 높았다. 또한, 제안된 방법을 기반으로 얼굴의 영구적인 특징과 일시적인 특징을 함께 표현하는 새로운 지역미세패턴의 개발이 가능함을 확인하였다.

• 한국통신학회논문지
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• 제33권10A호
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• pp.1006-1012
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• 2008

Duvall 구조에 기초하여 코히런트(coherent), 인코히런트(incoherent) 간섭을 제거하는 효율적인 적응 빔 형성방법을 제시한다. 하나의 상관벡터를 이용하는 기존방식과 달리, 제안된 방법에서는 여러 개의 상관벡터를 이용하여 가중벡터의 차원을 크게 한다. 가중벡터 차원의 증가로 빔 형성기의 SINR(signal-to-interference plus noise ratio) 성능을 개선할 수 있으며, 더 많은 간섭을 제거 할 수 있다. 시뮬레이션 결과에 따르면, 제안방식은 기존방식에 비해 빠른 수렴특성, 우수한 정상상태(steady-state)에서의 SINR 성능을 보여준다.

• 설비공학논문집
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• 제25권2호
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• pp.85-93
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• 2013

The proportional plus integral(PI) feedback control manner has been used in many general industrial fields such as refrigeration system because of its simple design process and favorable control performance. This paper deals with optimized PI controller design of the refrigeration system based on evaluation functions such as integrated absolute error(IAE). The suggested optimal PI gains can be easily calculated by a simple program and the optimal controllability satisfying the evaluation function can be assured. Furthermore, at the initial step of controller design, the suggested optimal gain is able to reflect some noise disturbances caused by an inverter which drives variable speed compressors. The validity of the suggested optimal gain is investigated by some simulations and experiments to verify its efficiency. From the results of comparing control performance between the optimal PI controller based on the evaluation function and the PI controller designed by the Matlab tuner which was known as the most popular gain tuner, the optimal PI controller showed more desirable control performance especially in transient responses.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.962-966
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• 2004

Ball screw feed drive systems have been broadly used in machine tools or precision automatic feed systems. Recently, modern machine tools require high speed and high precision and drive system to achieve high productivity. Unfortunately, a feed drive system, even though it was optimum designed, may experience severe transient vibrations during high-speed operation if its feed rate control is unsuitable. A rough feed rate curve having discontinuity in its acceleration profile causes a serious vibration problem in the feed slide system. This paper presents a feed rate optimization of a machine tool feed slide system, which is driven by a ball screw, for its minimum vibrations. Firstly, a 6-degree-of-freedom lumped parameter model was proposed for the vibration analysis of a ball screw driven machine tool feed drive system. Next, a feed rate optimization of the feed slide was carried out for minimum vibrations. The feed rate curve optimization strategy is to find out the most appropriate acceleration profile having finite jerk. Of course, the optimized feed rate should approximate to the desired one as possible. A genetic algorithm with variable penalty function was used in this feed rate optimization.

• 한국소음진동공학회논문집
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• 제19권2호
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.