• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.143-150
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• 1999

The vibration signals of driving parts of electric train are distorted its signal patterns due to the impact components, which occurs when wheel passes rail joints. An elimination method of the impact components is investigated using adaptive signal processing technique in this study. The result shows that adaptive interference canceling method seems to be more effective than line enhancement technique. The application of adaptive interference canceling method to the signal measured at bogie shows that the extractions of the signals of driving parts of traction motor, reduction gear, and axle bearing are successful. Therefore, only the signals of bogie, which is the place to attach an accelerometer easily, is sufficient for the fault diagnosis and the safety evaluation of electric train. Also, adaptive interference canceling method can be applicable to evaluate the performance of vibration isolation between bogie and car body and to investigate the characteristics of indoor sound.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.1038-1042
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• 2003

In order to evaluate dynamic impedance of a hand-arm system it is necessary to measure the hand-transmitted vibration and the reaction force at the same time while gripping the vibrating handle. In the study a device was developed to measure both the vibration and the force. The device consists of a measurement handle with four strain gauge and two accelerometers and a PC based control system with a program for the signal processing and evaluation of the hand-transmitted vibration and reaction force. The handle was installed on the vibration shaker so that it can move by the generated signal from the control system. As an application of the system dynamic reaction force and the frequency weighted acceleration at the handle attached to the shaker were measured at various grip force and feed force. This system will be very useful in the area of impedance measurement and the evaluation of performance of anti-vibration gloves.

• 전자공학회논문지 IE
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• 제47권4호
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• pp.18-27
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• 2010

본 논문은 회전체의 진동 데이터를 효율적으로 획득하기 위해 데이터 획득 시스템을 설계하였다. 데이터획득 장치는 필터와 증폭기로 구성한 아날로그 로직과 ADC와 DSP, FPGA, FIFO 메모리를 갖고 있는 디지털로직으로 구성하였다. 센서로부터 회전체의 진동신호는 아날로그 로직을 통과하여 FPGA에 의해 제어되고, 그 신호는 ADC를 통해 변환되고 FIFO 메모리에 저장하였다. 디지털 선호 처리는 FPGA 제어어의해서 FIFO 메모리에 들어온 데이터를 이용하여 DPS에서 신호처리를 수행할 수 있도록 구성하였다. 회전체 진동을 진단 및 분석하기 위한 진동 요소는 데이터 선호로서 실수 변환, Peak to Peak, 평균 값 산출, GAP, 디지털 필터, FFT 둥을 DSP에서 처리하고 설정된 이벤트를 추적하며, 그 결과 값을 도출하여 조기 경보 구축하였다 묘든 신호처리 과정 및 이벤트 추적은 여러 분석 단계 의해서 처리 시간이 소요되며, 특정 이벤트에 따라 처리 소요 시간에도 변동이 발생한다. 데이터 획득 및 처리는 연속적으로 실시간 분석을 수행해야 하지만, DSP에서는 입력된 신호를 처리하는 동안에 입력된 이후의 데이터에서 다음 입력처리 시간동안 획득한 데이터는 처리 될 수 없고, 특히 다수의 채널에서는 더 많은 데이터 손실이 일어날 수 있다. 따라서 본 논문에서는 데이터 손실이 적고 빠른 처리를 위하여 DPS와 FPGA을 효과적인 사용하였고, 이러한 여러 분석 단계 신호처리에서 발생되는 시간을 최소한으로 줄일 수 있는 방법으로 DSP에서 처리되는 신호단계 중 일부를 FPGA에서 처리할 수 있도록 설계 하였고 그리고 단일의 신호 처리에 의해 수행되는 분석 단계를 병렬 처리로 데이터를 실시간으로 처리하였다. 그 결과로 DSP 만으로 구성된 신호처리 보다 DSP와 FPGA로 구성된 시스템이 훨씬 빠르고 안정된 신호 처리 방법을 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.694-695
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• 2013

An experimental study has been made with the use of time reversal concepts to recover the input waveform in a long range propagation of dispersive Lamb waves. Three techniques have been tested: Regular TR, 1 bit TR and Inverse filter (IF). The IF approach was found to completely recover the original input signal. Moreover, the IF technique significantly increases the contrast, i.e., the ratio of the recovered signal and the sideband signal.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.361-364
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• 2003

The safe operation and reliable maintenance of nuclear power plants is one of the most fundamental and important tasks. It is known that a loose part such as a disengaged and drifting metal inside of reactor coolant systems might lead to a serious damage because of their impact on the components of the coolant system. In order to estimate the impact position of a loose par, three accelerometers attached to the wall of the coolant system have been used. These accelerometers measure the vibration of the coolant system induced by loose part impact. In the conventional analysis system, the low pass filtered version of the vibration data was used for the estimation of the position of a loose part. It is often difficult to identify the initial point of the impact signal by using just a low passed time signal because the impact wave is dispersed during propagation into the sensor. In this paper, the impact signal is analysed by use of various time frequency methods including the short time Fourier transform(STFT), the wavelet transform, and the Wigner-Vill distribution for finding a convenient way to identify the starting point of a impact signal and their advantages and limits are discussed.

• 한국소음진동공학회논문집
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• 제20권9호
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• pp.863-875
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• 2010

The vibration of a cylindrical shell is generated due to elastic waves propagating on the shell. Those elastic waves include propagating waves such as flexural, longitudinal and shear waves. Those also include non-propagating decaying waves, i.e. evanescent waves. In order to separate contributions of each type of waves to the data for the vibration of the cylindrical shell, spatial signal processing techniques for wavenumber analysis are investigated in this paper. Those techniques include Fast Fourier transform(FFT) algorithm, Extended Prony method and Overdetermined Modified Extended Prony method(OMEP). Those techniques have been applied to identify the waves from simulated vibration signals with various signal-to-noise ratios. Futhermore, the experimental data for in-plane vibration of the cylindrical shell has been processed with those techniques to identify propagating waves(longitudinal, shear and flexural waves) and evanescent waves.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1142-1147
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• 2002

For the evaluation of the DC motor noise and vibration, usually it is rely on human feeling because some kinds of noise are not definitely represented by measurement Instrument such as sound meter. But when we consider time signal of the noise and vibration. It is possible to represent them. And in this paper. it is suggested to study output current shape of the motor because it Is the source to make speed and torque variation of the motor. If the current shape is not stable. it makes operating state of the motor unstable and produces noise and vibration. By analyzing signal at time and frequency of noise and vibration and current shape. it is possible to automation of the noise and vibration measurement in the Production line.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.87-93
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• 2017

This paper investigates active noise control of tower-type air conditioners using the filtered-x least mean square (FXLMS) algorithm to reduce fan blower noise transmission. Firstly, the main components required for the active control system including the error sensor, the control speaker and the reference sensors are selected. Since the noise could significantly reduce if the reference signal includes every frequency response information, a various reference signals from accelerometers and a microphone are used. Secondly, the controller based on the FXLMS algorithm with a single-channel reference signal is implemented. Then, the control performance is examined experimentally for the different reference signals. It is found that the accelerometer signal well possesses the motor vibration related noise and a microphone signal could includes global noise. When using the reference signal with a microphone located near the motor and the fan blower, the active control system reduces the noise globally, except for several peaks.

• 한국생산제조학회지
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• 제9권5호
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• pp.157-164
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• 2000

A machine tool generally has some serious stability problems in the form of tool chatter during the cutting process. Chatter vibration deteriorates the surface finish, reduce tool and machine life, accelerates machine tool system component wear, and may lead to an unacceptable noise sound in the working environment. In this study, the behavior of spectral density of AE signal and principal cutting force signal in order to monitor the chatter vibration in the cutting process has been investigated. From the results, the reliability of proposed monitoring method has been confirmed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.150-155
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• 2006

Speech intelligibility is investigated on a conference room-window glass coupled system. Using MLS(Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the window glass are measured by accelerometer and laser doppler vibrometer. MTF(Modulation Transfer Function) is used to identify the speech transmission characteristics of the room and window system. STI(Speech Transmission Index) is calculated by using MTF and speech intelligibility of the room and the window glass is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared and the possibility of the wiretapping is investigated. Finally, intelligibility of the conversation sound is examined by the subjective test.