• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.481-490
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• 2021

In the ultrasonic welding machine, when the load fluctuates, the L and C of the piezo element in the oscillation part change. As a result, the resonant frequency is changed, so it is necessary to match the operating frequency of the ultrasonic welding machine to the new resonant frequency. That is, in order to maximize the output of the oscillation unit of the ultrasonic welding machine, it is inevitable to follow the resonance frequency. Accordingly, many methods for following the resonant frequency are being actively studied. In addition, in order to check the effect of external inductance on the operation of the ultrasonic welding machine, The equivalent circuit of the piezo element was analyzed by including the external inductance for resonance in the equivalent circuit of the piezo element, and the method of selecting an appropriate inductance was described. In this paper, we propose a new system that allows the switching frequency of the inverter to tracking the resonance frequency even if the resonance frequency is changed due to the load of the ultrasonic welding machine.

• 동력기계공학회지
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• 제5권3호
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• pp.31-37
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• 2001

A study to obtain the enhancement of turbulence at low Reynolds number is carried out by adding ultrasonic force into the jet flow field of a coaxial circular pipe which can afford the sufficient data of flow characteristics with the shear flow and turbulence flow in spite of its simple shape. A coaxial circular flow field is made vertically in a large and transparent acryl tank. The time mean velocity vector, distribution, kinetic energy and turbulence intensity formed in the complex flow field of turbulence enhancement are investigated, observed and discussed at Reynolds number of 2,000, 3,000 and 5,000 by using PIV measurement, in results, the validity of ultrasonic to obtain the enhancement of turbulence is certified.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1155-1160
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• 2007

This paper presents position error for the robot localization system using the ultrasonic wave. The distance between the receiver and a beacon can be computed by using the difference between times of flight. The distance information measured by ultrasonic wave has errors. The position is calculated by distances, and this error is caused by distance errors. The position error is different from receiver¡s position. And the position is also calculated by beacon location. This paper calculates worst case position error within measuring area, and finds beacons location to reduce the position error.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.89.5-89
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• 2001

In this paper we explain about systems developed to forecast the standing up of the dementia patients. Basic idea of our approach is to measure the respiration and body movements in the bed. Based on the data measured, forecasting of standing up action from the bed is possible to some extent. First system proposed uses an image processing technique. Data obtained about the respiration and movements are used to forecast the standing up of the patients. The second system uses ultrasonic sensors, which emits and receives ultrasonic signals. Two techniques f the ultrasonic sensors are considered. One technique is to emit ultrasonic burst signals and to detect the instance when ...

• 한국기계가공학회지
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• 제12권5호
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• pp.135-140
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• 2013

Ultrasonic cutting is a kind of eco-technique and cost-effective technique to be used for cutting of various materials such as baked product, fresh/frozen food, rubber, textile, wood, bone, etc. The performance of ultrasonic cutting is affected by design of cutting horn and cutting conditions. Specially the design of horn to resonate at the longitudinal direction is most important. To analyze the problems from which cracking and noise are often generated with conventional cutting horn, FEA is carried out, and then improved cutting horn which can reduce maximum stress and stress concentration is designed. Vibration characteristics, resonant frequency, gain, and amplitude uniformity of the cutting horn designed optimally are evaluated through FFT analysis and compared with those of conventional cutting horn.

• 설비공학논문집
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• 제16권1호
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• pp.77-83
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• 2004

In this study, the spray cooling heat transfer and working characteristics of the screen wick heat pipe with ultrasonic spray cooling system in condenser were experimentally investigated. The heat pipe was made of copper tube 300 mm long with inner diameter of 11.1 mm. The evaporator and condenser lengths of heat pipe were 40, 200 mm and the wick structure consists of two layer of 100 mesh copper screen. The experimental results show that the ultrasonic spray cooling increases the heat transfer rate on the condenser surface, and the total thermal resistance of heat pipe system decreases remarkably. A comparison is made for the two working fluids, water and ethanol. The surface temperature of the ethanol tube in evaporator section becomes higher than that of the water tube. Thus, the experimental result shows that water is more useful than ethanol as the working fluid because of increasing the operational limit within this experimental conditions.

• 전기학회논문지
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• 제67권8호
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• pp.1089-1098
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• 2018

In this paper, we propose an autonomous feeding robot and its obstacle classification system using ultrasonic sensors to secure the driving safety of the robot and efficient feeding operation. The developed feeding robot is verified by operation experiments in a cattle shed. In the proposed classification algorithm, not only the maximum amplitude of the ultrasonic echo signal but also two gradients of the signal and the variation of amplitude are considered as the feature parameters for object classification. The experimental results show the efficiency of the proposed classification method based on the Support Vector Machine, which is able to classify objects or obstacles such as a human, a cow, a fence and a wall.

• 한국식품과학회지
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• 제53권5호
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• pp.527-534
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• 2021

The demand for sustainable extraction of bioactive compounds from food matrices has been increasing. Water extraction of anthocyanins in aronia was investigated using conventional and ultrasonic-assisted methods. The optimum extraction conditions for the conventional method included a sample-to-water ratio of 1:40 g/mL, extraction temperature 71℃, and extraction time of 39 min. The optimized conditions for ultrasonic-assisted extraction were a sample-to-water ratio of 1:40 g/mL, extraction temperature 80℃, extraction time of 20 min, and an amplitude of 87.2 ㎛. The anthocyanin contents of the two extracts were 155.32 and 158.02 mg/100 g fresh weight, respectively. The major anthocyanins were cyanidin 3-galactoside (65% of the total) and cyanidin 3-arabinoside (30% of the total). The contents of individual anthocyanins and phenolic acids were not significantly different between the two optimized extracts.

• 항공우주시스템공학회지
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• 제15권3호
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• pp.99-104
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• 2021

멀터콥터형 드론에 적용할 목적으로 바람 센서의 특성을 분석하고 실험을 통하여 비교하였다. 회전식 풍속계의 경우 동역학 효과가 측정 오차를 만들며, 초음파식 센서는 제작 오차와 신호처리 오차가 주요한 것으로 나타났다. 초음파식 센서는 트랜스듀서의 거리가 멀수록 오차가 줄어든다. 실험을 통하여 이러한 특성들을 확인하였으며, 멀티콥터에는 전압 출력 혹은 10 hz 이상의 데이터 출력이 가능한 초음파식 센서가 적합하다고 판단한다.

• 한국산업정보학회논문지
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• 제22권5호
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• pp.25-30
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• 2017

본 논문에서는 초음파 센서를 이용한 저비용 장애물 인식 장치를 개발한다. 개발된 장애물 인식 장치는 시각 장애인들이 보행시 장애물을 인식하는 데 쓰일 수 있도록 한다. 장애물의 인식 여부는 내장된 모터의 진동을 통하여 시각 장애인들에게 인식이 가능하도록 한다. 뿐만 아니라 장애물의 거리에 따라 대상자에게 장애물 인식 유무에 대해 시간차를 두고 고지하여 대상자가 장애물에 대해 적절한 반응을 수행할 수 있도록 한다. 마이크로 컨트롤러 제어를 통한 펄스 신호를 이용하여 장애물에 대한 반사파를 통해 장애물의 존재 유무와 거리를 탐지하며 펄스 신호를 이용한 반사파 탐지는 반복 수행을 통해 인식률을 높인다. 개발된 장애물 인식 장치는 $30^{\circ}$ 내외의 전방 탐지각을 나타내고, 2cm-30cm의 탐지거리를 가지며 일상적인 보행 조건에서 동작이 가능함을 실험을 통해 입증하였다.