• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.86-97
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• 2009

RTLS is a system for automatically locating and tracking people and objects. The TDOA-based RTLS determines the location of the tag by calculating the time differences of a signal received from the tag. In TDOA-based RTLS, time synchronization is essential to calculate the time difference between readers. This paper presents a precision time synchronization method for TDOA-based RTLS over IEEE 802.15.4. In order to achieve precision time synchronization in IEEE 802.15.4 radio, we analyzed the error factors of delay and jitter. We also deal with the implementation of hardware assisted time stamping and the Kalman filtering method to minimize the error factors. In addition, this paper described the experiments and performance evaluation of the proposed precision time synchronization method in IEEE 802.15.4 radio. The results show that the nodes in a network can maintain their clocks to within 10 nanoseconds offset from the reference clock.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.367-372
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• 2012

This paper presents a development of an analog type magnetic positioning system and its positioning accuracy improvement using fuzzy inference system. As the magnetic positioning system used on a magnet-gyro guidance system for AGV(automatic guided vehicle), it measures a position of magnet embedded in floor of the work place. The existing product of the magnetic positioning system is very expensive in Korea because it is being sold in a foreign country exclusively. Moreover, the positioning accuracy of the product is low because it uses digital type unipolar hall sensors. Hence, we developed the magnetic positioning system by ourselves and improved the positioning accuracy of the developed magnetic positioning system using fuzzy inference system. For experiment, we used the analog type magnetic positioning system which we have developed, and compared the performance of the proposed method with the performance of the existing positioning method for the magnetic positioning system. In experimental results, we verified that the proposed method improved the positioning accuracy of the magnetic positioning system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.61-69
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• 2006

Position determination accuracy is strongly depending on how much precisely and frequently satellite receiver measures transmitted signals from terminals on target animals when Doppler effect is applied for position determination. ARGOS satellite system has shown relatively high position determination accuracy by operating multiple satellites, which enable operator to get more Doppler shift data from terminals. In case of animal tracking mission with single satellite, however, it is difficult for the satellite receiver to receive transmitted signals from terminals frequently during short period that satellite passes over ground terminals. This is one of the main sources to decrease position accuracy on target animals. In this paper, the Doppler rate estimation is implemented to increase the number of Doppler shift data received by single satellite. It is proved that the relatively high position determination accuracy with increased number of estimated data can be obtained. We also suggest that the Doppler rate estimation is applicable for position determination system with single satellite.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.5
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• pp.667-672
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• 2011

This paper presents to study the sensor fusion of positioning sensors using UKF(unscented Kalman filter) for positioning accuracy improvement of AGV(automatic guided vehicle). The major guidance systems for AGV are wired guidance and magnetic guidance system. Because they have high accuracy and fast response time, they are used in most of the FMS(flexible manufacturing system). However, they had weaknesses that are high maintenance cost and difficult of existing path modification. they are being changed to the laser navigation in recent years because of those problems. The laser navigation is global positioning sensor using reflecters on the wall, and it have high accuracy and easy to modify the path. However, its response time is slow and it is influenced easily by disturbance. In this paper, we propose the sensor fusion method of the laser navigation and local sensors using UKF. The proposed method is improvement method of accuracy through error analysis of sensors. For experiments, we used the axle-driven forklift AGV and compared the positioning results of the proposed method with positioning results of the laser navigation. In experimental result, we verified that the proposed method can improve positioning accuracy about 16%.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2001.10a
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• pp.71-82
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• 2001

인공위성을 이용한 범 지구 위치결정시스템인 GPS(Global Positioning System)는 수 밀리의 정밀도로 정적, 동적 위치측정이 가능한 시스템으로 교량, 건축물, 댐 등 각종 구조물의 미세한 변위를 측정하는데 이용되고 있다. 최근 국내에서도 대형구조물의 변위 측정에 GPS를 활용하려는 시도가 부분적으로 이루어지고 있으나 초보적인 단계이며 체계적인 연구가 이루어지지 못하고 있는 실정이다. 본 연구에서는 RTK(Real Time Kinematic) GPS로 구조물의 변위를 실시간 측정하고 모니터링 할 수 있는 시스템을 개발하였다. 먼저 예비실험으로 반송파의 차분에 의해서 증폭되는 수신기의 측정잡음 오차, 다중경로 오차, GDOP(Geometric Dilution of Precision)가 RTK GPS의 위치정확도에 미치는 영향을 분석하였다. 그리고, RTK GPS를 이용하여 마포대교를 관측한 결과, 수 센티미터 정도 발생하는 구조물의 변위를 3차원으로 정밀 관측할 수 있었으며, 본 연구에서 개발한 모니터링프로그램을 이용하여 구조물의 거동을 실시간으로 모니터링 할 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.82-89
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• 1999

미국의 전파항법정책(FRP Federal Radionavigation Plan)은 여전히 SA정책(미국방성에서 GPS 위성 궤도에 오차를 실어 전파발사를 하는 정책)을 유지하고 있고, P(Y)코드 접속에 의한 고정밀 위치정보 사용 역시 미군 및 NATO군 등 미 국방성에서 인가한 사용자에게만 허용되고 있는 관계로 그 외의 사용자는 3차원 고정밀 위치정보가 요구되는 항공기 이착륙 유도시스템, 해ㆍ육상 정밀 구조/탐색 및 육ㆍ해ㆍ공 특수목적 등에 군사용 P(Y)코드대신 DGPS를 사용하고 있다. 본 연구는 한반도 남해안 및 동해안 일부까지를 유효거리로 하고 있는 일본 Marine Radiobeaeon/DGPS 시스템에 대한 한반도 연근해에서의 위치정보 사용 가능성을 확인하기 위해 한반도 남해안에서 측정 가능한 일본 DGPS국을 선택 모델로 하여 DGPS Data 측정실험 및 위치정보 정밀도 분석을 하였다. 연구결과 군사용 P(Y) 코드수준의 정밀도를 유지하고 있어 곧 구축 예정인 한국형 DGPS 국가망과 함께 선택적으로 사용할 수 있음을 확인하였다.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.5
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• pp.706-711
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• 2008

This paper is presented an accurate localization scheme for mobile robots based on the fusion of ultrasonic satellite (U-SAT) with inertial navigation system (INS), i.e., sensor fusion. Our aim is to achieve enough accuracy less than 100 mm. The INS consist of a yaw gyro, two wheel-encoders. And the U-SAT consist of four transmitters, a receiver. Besides the localization method in this paper fuse these in an extended Kalman filter. The performance of the localization is verified by simulation and two actual data(straight, curve) gathered from about 0.5 m/s of driving actual driving data. localization methods used are general sensor fusion and sensor fusion through Kalman filter using data from INS. Through the simulation and actual data studies, the experiment show the effectiveness of the proposed method for autonomous mobile robots.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.162-162
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• 2004

위치결정 기술은 초정밀 미세 기술의 발달과 제품의 소형화, 경량화에 대한 요구가 늘어나면서 고정밀화가 가속화되어 현재는 나노미터 수준의 위치정밀도를 요구하고 있다 현재 널리 사용되어지는 표면형상 측정기인 AFM은 분해능과 정밀도는 우수하지만, 이송 스테이지의 제한으로 측정영역이 좁은 단점이 있다. 이를 극복하기 위해서 이중서보를 사용한 방식들이 많이 제안되어 왔고 단일 서보를 사용하는 방식들도 연구되고 있다. 하지만 이중서보 방식은 여러 가지 액츄에이터와 컨트롤러를 사용해야하므로 제어알고리즘과 시스템이 복잡해지는 단점을 가지고 있다.(중략)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.401-407
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• 2010

As according to utilizing mobile devices, the real time locating system to provide high quality service is required. RTLS based on wireless communication can be damaged from radio shadow areas which guarantee the line of sight. To cope with the radio shadow area, this paper proposes the performance improvement method using assistant tags and a directional antenna based reader. In addition, this paper also provides the design and implementation of RTLS and experiments for performance evaluation. The result shows that a success rate is increased up to 38% and accuracy is a CEP of 1.13 meters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.879-884
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• 2015

Printed electronics is a technology that produces electronic devices and circuits by printing functional ink on a web, which is a film-like flexible material. This technology is suitable for large-scale and high-speed mass production, and is a next-generation process technology that can fabricate electronic devices from flexible materials. As precise measurement of the positions of the web is required in order to commercialize such a printed electronics process, a measurement system with an optical encoder with a precision of micrometers had been proposed in the preceding research of this study. However, the lateral positions of the web could not be measured in the preceding research as the phenomenon of the entire web being moved in the lateral direction could not be detected. In this study, a measurement system that utilizes the differences in the amount of light reflected from the alignment patterns depending on the web positions in the lateral direction was proposed for measuring the lateral positions of the web. In addition, its reliability was verified and then the effect when measuring printed alignment patterns was analyzed by experiments.