• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.641-647
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• 2003

The use of infrared range-finder sensor as the environment recognition system for mobile robot have the advantage of low sensing cost compared with the use of other vision sensor such as laser finder CCD camera. However, it is not easy to find the previous works on the use of infrared range-finder sensor for a mobile robot because of the non-linear characteristic of that. This paper describes the error due to non-linearity of a sensor and the correction of it using neural network. The neural network consists of multi-layer perception and Levenberg-Marquardt algorithm is applied to learning it. The effectiveness of the proposed algorithm is verified from experiment.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.81-87
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• 2007

It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. However, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis and artificial neural network were used as the research methods. And, the results of two prediction methods were compared and analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.184-191
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• 2008

In order for a mobile robot to move under unknown or uncertain environment, it must have an environmental information. In collecting environmental information, the mobile robot can use various sensors. In case of using ultrasonic sensors to collect an environmental information, it is able to comprise a low-cost environmental recognition system compared with using other sensors such as vision and laser range-finder. This paper proposes a map building algorithm which can collect environmental information using ultrasonic sensors. And also this paper suggests a traveling algorithm using environmental information which leads to the map building algorithm. In order to accomplish the proposed traveling algorithm, this paper additionally discusses a position revision algorithm.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.11a
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• pp.207-210
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• 2006

자동차 추돌 방지용 레이더는 도로 사정이나 기후에 따른 운전자의 인지 및 판단이 불가능한 상황에서도 차량 간의 추돌을 예방할 수 있는 시스템이다. 현재까지 연구 개발된 차량용 레이더는 초음파나 밀리미터 웨이브 등을 이용하므로 가격이나 크기 등에서 경쟁력을 갖추지 못하고 있는 실정이다. 따라서 본 논문에서는 적외선 레이저 다이오드를 매트릭스 형태로 배열한 다중 파장 구조 방식을 제안하였다. 이는 악천후에서의 탐지 능력을 개선시킬 수 있다. 또한 의사 잡음 수열의 상관 특성을 이용하여 인접 차량의 레이저 신호에 의한 간섭 영향을 최소화시킬 수 있기 때문에 차세대 ITS 기술 선점 및 산업 경쟁력을 확보 등의 효과를 기대할 수 있다.

• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.74-82
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• 2001

Visual cryptography made it possible to decrypt the Information encrypted by thresholding scheme not with digital system but with human vision system. This method, however, has some limit in it because of the rack of resolution in both the spatial and amplitude domain. Optical visual cryptography, which used laser system instead of human eyesight, was proposed by conjunction of the optical theory with the cryptography. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. The problem occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. In this paper, we analysis, in the aspect of frequency, the security characteristics and the noise level occurred in the process of optical visual encryption.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.217-223
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• 2016

In this research, a continuous roll-to-roll screen printing system was developed using a flat screen. It has a newly devised sliding mechanism of screen printing module, which can be controlled accurately in sync with a moving web, driven by a roll-to-roll tension control and web-guiding system. In addition, the real-time precision alignment module that consists of a vision camera and an $X-Y-{\theta}$ alignment stage was implemented. With this developed system, the feasibility of continuous printing with minimum pattern width below $60{\mu}m$ was verified, and an overlay of ${\pm}60{\mu}m$ between the laser-patterned reference mark and the printed mark on a 300-mm-wide film was achieved.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.353-361
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• 2011

A precise embedded ultrasonic localization system is developed for autonomous mobile robots in indoor environments, which is essential for autonomous navigation of mobile robots with various tasks. Although ultrasonic sensors are more cost-effective than other sensors such as LRF (Laser Range Finder) and vision, they suffer inaccuracy and directional ambiguity. First, we apply the matched filter to measure the distance precisely. For resolving the computational complexity of the matched filter for embedded systems, we propose a new matched filter algorithm with fast computation in three points of view. Second, we propose an accurate ultrasonic localization system which consists of three ultrasonic receivers on the mobile robot and two or more transmitters on the ceiling. Last, we add an extended Kalman filter to estimate position and orientation. Various simulations and experimental results show the effectiveness of the proposed system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.589-597
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• 2003

Visual cryptography made it possible to decrypt thresholding scheme with not digital system but human vision system. This method, however, has some limit in it. Optical visual cryptography was proposed which used laser instead of human eyesight. As a result, it was possible to adapt cryptography to optical system. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. These problems occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. This paper analyzes the level of noise and the security characteristics for optical visual cryptography in terms of frequency based on joint transform correlator.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.2
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• pp.85-92
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• 2003

In this paper, we propose a method to evaluate performances of mobile personal robots. A set of performance measures is proposed and the corresponding evaluation methods are developed. Different from industrial manipulators, personal robots need to be evaluated with its mobility, navigation, task and intelligent performance in environments where human beings exist. The proposed performance measures are composed of measures for mobility including vibration, repeatability, path accuracy and so on, as well as measures for navigation performance including wall following, overcoming doorsill, obstacle avoidance and localization. But task and intelligent behavior performances such as cleaning capability and high-level decision-making are not considered in this paper. To measure the proposed performances through a series of tests, we designed a test environment and developed measurement systems including a 3D Laser tracking system, a vision monitoring system and a vibration measurement system. We measured the proposed performances with a mobile robot to show the result as an example. The developed systems, which are installed at Korea Agency for Technology and Standards, are going to be used for many robot companies in Korea.

• Computers and Concrete
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• v.31 no.5
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• pp.457-468
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• 2023

Buildings, bridges, and dams are examples of civil infrastructure that play an important role in public life. These structures are prone to structural variations over time as a result of external forces that might disrupt the operation of the structures, cause structural integrity issues, and raise safety concerns for the occupants. Therefore, monitoring the state of a structure, also known as structural health monitoring (SHM), is essential. Owing to the emergence of the fourth industrial revolution, next-generation sensors, such as wireless sensors, UAVs, and video cameras, have recently been utilized to improve the quality and efficiency of building forensics. This study presents a method that uses a target-based system to estimate the dynamic displacement and its corresponding dynamic properties of structures using UAV-based video. A laboratory experiment was performed to verify the tracking technique using a shaking table to excite an SDOF specimen and comparing the results between a laser distance sensor, accelerometer, and fixed camera. Then a field test was conducted to validate the proposed framework. One target marker is placed on the specimen, and another marker is attached to the ground, which serves as a stationary reference to account for the undesired UAV movement. The results from the UAV and stationary camera displayed a root mean square (RMS) error of 2.02% for the displacement, and after post-processing the displacement data using an OMA method, the identified natural frequency and damping ratio showed significant accuracy and similarities. The findings illustrate the capabilities and reliabilities of the methodology using UAV to evaluate the dynamic properties of structures.