• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1046-1050
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• 2003

In this paper, we describe study on the development or multi-path ultrasonic gas flowmeter using a transit time method. This system includes 5 pairs of ultrasonic transducers. ultrasonic signal processing unit using switch matrix method, computation algorithm of gas flow rate, spool piece type multi-path pipe unit. We have developed enhanced type of main ultrasonic signal processing unit using switch matrix method fer multi-path ultrasonic gas flowmeter. Also, we have developed the new transmitting ＆ receiving method of ultrasonic waves and the new signal processing algorithm for the computation of ultrasonic transit time from received ultrasonic waves. In this study, we have designed more compact signal processing unit compared with the conventional hardware system of multi-path ultrasonic gas flowmeter. We have confirmed its reliability for multi-path ultrasonic gas flowmeter through the laboratory test using calibration system. In the future. we will perform the field test for the developed system in the POSCO gas line.

• 제어로봇시스템학회논문지
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• 제9권2호
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• pp.145-151
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• 2003

A global ultrasonic sensor system for self-localization of a mobile robot is proposed in this paper. The global ultrasonic sensor system consists of three or more ultrasonic transmitters fixed at some positions in the world coordinate and receivers in the moving coordinate of a mobile robot. In this global sensor system it is easy to get state vector of the mobile robot in the world coordinate from the distance information between each ultrasonic transmitter and receiver. An extended kalman filter algorithm is used to process the noisy ultrasonic signal and to estimate the state vector. In case of using several independent ultrasonic transmitters, it is necessary to avoid the cross talk among the ultrasonic waves and to synchronize between each ultrasonic transmitter and receiver. The small sized radio frequency modules are adopted to solve the cross talk and the synchronization problem Computer simulation and experiments are carried out to verify the effectiveness of the proposed ultrasonic sensor system.

• 한국전기전자재료학회논문지
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• 제31권3호
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• pp.152-155
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• 2018

Ultrasonic wave technologies have been widely used in ultrasonic washing machines, ultrasonic surgery, ultrasonic welding machines, ultrasonic sensors, and medical instruments. Ultrasonic surgery can be realized through the cavitation effect of ultrasonic waves. In this study, piezoelectric ceramics were manufactured to achieve the optimum design of a piezoelectric vibrator in a handheld generator for ultrasonic surgery. The best specimen showed the excellent piezoelectric properties of kp＝0.624, Qm＝1,531, and $d_{33}=356pC/N$. Numerical modeling based on the finite element method was performed to find the resonance frequency, the anti-resonance frequency, and the displacement properties of the handheld ultrasonic generator. Maximum displacement was observed in the six-step piezoelectric vibrator at $6.36{\mu}m$.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권6호
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• pp.297-303
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• 2002

We have developed an on-line ultrasonic detector to monitor partial discharge in an operating transformer. The ultrasonic sensor has 150[KHz] resonance frequency and contains a pre-amplifier with 60[㏈] gain. The on-line ultrasonic detector has 50~300[KHz] frequency band-pass filter to remove electrical and mechanical noises from the transformer. This detector has an ultrasonic signal discrimination algorithm which discriminates ultrasonic signals due to partial discharge in a transformer. A moving average method of ultrasonic signal number was employed to effectively monitor the increasing trend of the partial discharge. This paper describes an experience of partial discharge detection in a 154[㎸] operating transformer using an ultrasonic detector. With regards to gas analysis in oil, C2H2 gas was produced with a warning level in this transformer We detected ultrasonic signals on the transformer steel wall, and estimated the position of partial discharge. With further inspection, we found carbonized marks due to partial discharge on the supporting bolt which fastens the windings.

• 전자공학회논문지
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• 제54권1호
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• pp.152-156
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• 2017

지금까지의 초음파센서와 관련된 연구 중 대부분은 대기 중에서 사용하거나 수중에서 사용하는 연구가 대부분이었다. 본 연구는 원유나 석유 등의 유종에서 사용하는 경우에 관한 것으로 초음파 소자에 고전압을 인가해야 하는 초음파의 특성 상 폭발의 위험이 있어 폭발에 대한 우려 없이 유종에서 초음파를 효과적으로 발생시키기 위한 초전도 셀의 특성에 대해 연구하였다. 본 연구를 통해 폭발의 위험이 없으면서 원유 등 유종에서 초음파를 투과하여 원유의 깊이를 측정하거나 원유 바닦의 슬러지를 측정할 수 있는 가장 적합한 초전도셀의 면적, 두께, 발사 주파수 등을 도출하였으며 초음파센서에 24V의 전압을 인가하여 200kHz 주파수를 발생시킬 경우, 초전도셀의 최적 직경은 26~28mm, 두께는 9mm로 하는 것이 최적임을 확인하였다.

• Environmental Engineering Research
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• 제11권2호
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• pp.99-105
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• 2006

A digital ultrasonic image construction system was developed for the nondestructive detection of cracks in water distribution pipes. The system consists of PC based ultrasonic testing system and a scanning device. The PC based ultrasonic system has an ultrasonic pulse/receive board for the generation and reception of ultrasonic signals, an analogue to digital conversion board for the digitization of the received ultrasonic signals, and transducers for the ultrasonic sensors. Using this system, the digitized ultrasonic signals were properly constructed in accordance with the position information obtained by scanning device that moves an ultrasonic transducer along the outer surface of pipes. In the construction of the ultrasonic signals, signal processing concepts, such as spatial average and array concept, were considered to enhance the resolution of ultrasonic images of pipe wall. Using the developed system, crack detection experiments were performed in both laboratory and field, which shows promise for crack detection in the water distribution system.

• 제어로봇시스템학회논문지
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• 제17권2호
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• pp.79-87
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• 2011

This paper presents the optimal design of an overlapped ultrasonic sensor ring for high resolution obstacle detection of an autonomous mobile robot. It is assumed that a set of low directivity ultrasonic sensors of the same type are arranged along a circle of nonzero radius at a regular spacing with their beams overlapped. First, taking into account the dead angle region, the entire range of obstacle detection is determined with reference to the center of an overlapped ultrasonic sensor ring. Second, the optimal design index of an overlapped ultrasonic sensor ring is defined as the area closeness of three sensing subzones resulting from beam overlap. Third, the lower and upper bounds on the number of ultrasonic sensors are derived, which can guarantee minimal beam overlap and also avoid excessive beam overlap among adjacent ultrasonic sensors. Fourth, employing a commercial low directivity ultrasonic sensor, an optimal design example of an overlapped ultrasonic sensor ring is given along with the ultrasonic sensor ring prototype mounted on top of a mobile robot. Finally, some experimental results using our prototype ultrasonic sensor ring are given to demonstrate the validity and performance of an optimally overlapped ultrasonic sensor ring for high resolution obstacle detection.

• 제어로봇시스템학회논문지
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• 제13권10호
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• pp.956-961
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• 2007

We propose a new distance measurement method and local positioning system for the autonomous mobile robots localization. The distance measurement method is able to measure long-range distances with a high accuracy by using ultrasonic sensors. The time of flight of the ultrasonic waves include various noises is calculated accurately by the proposed period detecting method. The proposed local positioning system is composed of four ultrasonic transmitters and one ultrasonic receiver. The ultrasonic transmitter and receiver are separated but they are synchronized by RF (Radio frequency) signal. The proposed system using ultrasonic waves is represented as USAT(Ultrasonic Satellite System). USAT is able to estimate the position using the least square estimation. The experimental results show that the proposed local positioning system enables to estimate the absolute position precisely.

• 비파괴검사학회지
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• 제12권1호
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• pp.9-15
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• 1992

Ultrasonic spectroscopy is likely to become a very powerful NDE method for detection of microfects and thickness measurement of thin film below the limit of ultrasonic distance resolution in the opaque materials, provides a useful information that cannot be obtained by a conventional ultrasonic measuring system. In this paper, we considered a thin film below the limit of ultrasonic distance resolution sandwitched between two substances as acoustical analysis model, demonstrated the usefulness of ultrasonic spectroscopic analysis technique using information of ultrasonic frequency for measurements of thin film thickness, regardless of interference phenomenon and phase reversion of ultrasonic waveform. By using frequency intervals(${\triangle}f$) of periodic minima from the ratio of reference power spectrum of reflective waveform obtained a sample to power spectrum of multiple reflective waves obtained interference phenomenon caused by ultrasonic waves reflected at the upper and lower surfaces of a thin layer, can measured even dimensions of interest are smaller than the ultrasonic wave length with simplicity and accuracy.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1025-1031
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• 2000

An ultrasonic linear motors consist of a slider and an ultrasonic vibrator which generates an elliptical oscillations. The ultrasonic linear motors mainly consist of an ultrasonic vibrator which generates elliptical oscillations. The ultrasonic linear motor fabricated in this paper was the use of the 1st longitudinal(L1) and 4th bending vibrations(B4). In order to low driving voltage and improve the life time of the ultrasonic motor, we used stacked piezoceramics. Stacked piezoceramics are adhered to aluminum elastic material. The finite element method was used to optimize dimension of ultrasonic vibrator and direction of vibratory displacement. As a result of estimating the characteristics of the ultrasonic linear motor, no-load velocity was 0.204[m/s] when applied voltage was 70[ $V_{rms}$] in resonance frequency.y.