• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1826-1828
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• 2004

In this paper, we present an ultrasonic velocity and attenuation measurement system. There are many ultrasonic measurement methods that are used in nondestructive testing applications. They include material property determination, microstructural characterization, and flaw detection. Ultrasonic parameters such as velocity and attenuation are most commonly used in them. Advanced signal analysis which is called "ime-frequency analysis"has been used widely in nondestructive evaluation applications. Wavelet transform is the most advanced technique for processing signals with time-varying spectra. Using the echo waveform gathered by the designed hardware system, we performed simulation of the signal processing algorithms. Then the algorithm is implemented on the system.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.668-671
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• 2004

This paper proposes a new method of sensor fusion of an ultrasonic sensor and a vision sensor at the sensor level. In general vision system, the vision system finds edges of objects. And in general ultrasonic system, the ultrasonic system finds absolute distance between robot and object. So, the method integrates data of two different types. The system makes perfect output for robot control in the end. But this paper does not propose only integrating a different kind of data but also fusion information which receives from different kind of sensors. This method has advantages which can simply embody algorithm and can control robot on real time.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1463-1471
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• 2017

In order to monitor the pipe thinning caused by flow-accelerated corrosion (FAC) that occurs in coolant piping systems, a shear horizontal ultrasonic pitch-catch waveguide technique was developed for accurate pipe wall thickness monitoring. A clamping device for dry coupling contact between the end of the waveguide and pipe surface was designed and fabricated. A computer program for multi-channel on-line monitoring of the pipe thickness at high temperature was also developed. Both a four-channel buffer rod pulse-echo type and a shear horizontal ultrasonic waveguide type for high-temperature thickness monitoring system were successfully installed to the test section of the FAC proof test facility. The overall measurement error can be estimated as ${\pm}10{\mu}m$ during a cycle from room temperature to $200^{\circ}C$.

• Smart Structures and Systems
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• v.16 no.4
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• pp.667-681
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• 2015

The scour induced by strong currents and wave action decreases the embedded length of monopiles and leads to a decrease of their structural stability. The objective of this study is the development and consideration of scour-monitoring techniques for offshore monopile foundations. Tests on physical models are carried out with a model monopile and geo-materials prepared in a cylindrical tank. A strain gauge, two coupled ultrasonic transducers, and ten electrodes are used for monitoring the scour. The natural frequency, ultrasonic reflection images, and electrical resistivity profiles are obtained at various scour depths. The experimental results show that the natural frequency of the model monopile decreases with an increase in the scour depth and that the ultrasonic reflection images clearly detect the scour shape and scour depth. In addition, the electrical resistivity decreases with an increase in scour depth. This study suggests that natural frequency measurement, ultrasonic reflection imaging, and electrical resistivity profiling may be used as effective tools to monitor the scour around an offshore monopile foundation.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.62-71
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• 2009

In mobile robotics, ultrasonic sensors became one of the most popular devices for collision avoidance and navigation primarily due to data robustness, the easy availability of low-cost systems, their compact size, simple circuits, and their ease in interfacing with computers. However, ultrasonic sonic sensors are subject to noise which results in inaccuracy of mapping and localization of the robot. This paper introduces a new approach to enhance environmental maps based on ultrasonic range data using linear interpolation and Newton interpolation. The simulation and experimental results show that the proposed method improves of the accuracy of the map through better distance estimation between the mobile robot and obstacles.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1132-1135
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• 1996

The objective of this paper is to make a model-based map for the localization of an autonomous mobile robot(AMR) from ultrasonic sensor measurements, that are acquired when the AMR explores unknown indoors. First, the AMR navigates on unknown space by wall-following and gathers range data from the ultrasonic sensor. Then, the range data are converted to a wall-marked gird map, from which lines representing the walls are extracted using the Hough transform. This process is implemented on an AMR having an ultrasonic sensor, and a preliminary experimental result is presented.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.44.5-44
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• 2001

This paper proposes the algorithm which a mobile robot tracks the object captured by ultrasonic sensors of the robot and automatically generates a path according to the object In the proposed algorithm, a robot detects movements of the object as using ultrasonic sensors and then the robot follows the moving object. This algorithm simplifies robot path planning. The eight ultrasonic sensors on the robot capture distances between the robot and objects. The robot detects the movements of the object by using the changes of the distances captured by ultrasonic sensors. The target position of the robot is determined as the position of the detected moving object. The robot follows the object according to this movement strategy. The effectiveness of the proposed algorithm is verified through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.511-516
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• 1991

A new end-effector has been devised and the problems resulted from using it with SCARA robots are discussed. The end effector has two modules: one composed of two ultrasonic motors and two encoders for controlling each finger, and the other module composed of two ultrasonic motors and two encoders for controlling the wrist. The wrist module adds two degrees of freedom to the SCARA type robot, which generally has four degrees of freedom. With independent finger actuation and touch sensors, the gripper under computer control can feedback information about part size and part presence. Ultrasonic motors with high torque and slow motion characteristics are used. The principle of ultrasonic motors is explained and the servo characteristics of ultrasonic motors are studied. They are controlled by the general motion controller (Hewlett Packard HCTL-1000) which is linked to an IBM-PC AT.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.29-34
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• 2004

To investigate characteristics and micro-explosion of single-droplets of emulsified fuel, water is mixed with diesel oil by using ultrasonic energy fuel feeding system. The fuel characteristics is analysed through H-NMR spectrum and micro-explosion phenomena of the emulsified fuel is also investigated. The life times of droplets of conventional diesel fuel, ultrasonic energy added diesel fuel and emulsified fuel we obtained additionally. According to this study, the micro-explosion phenomena of single-droplets happen in atmospheric pressure condition, a curve form of emulsified fuel's life tim is different from diesel fuel's one and the change of chemical structures is a cause of ultrasonic-energy-added diesel fuel effect.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.1-7
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• 2004

This experiment was undertaken to investigate the atomization characteristics of the low viscosity biodiesel blended fuel and ultrasonic energy added one. Test fuels were conventional diesel fuel and biodiesel fuel. We compared to the characteristics of viscosity and surface tension, SMD between low viscosity biodiesel blended fuel and ultrasonic energy added one. Sauter mean diameter was measured under the variation of the spray distance. Viscosity and surface tension was measured under the variation of the time trace. To measure the droplet size, we used the Malvern system 2600C. Droplet size distribution was analyzed from the result data of Malvern system. Through this experiment, we found that the condition of the ultrasonic energy added situation had smaller Sauter mean diameter of droplet, viscosity and surface tension than that of the conventional situation.