• 한국산업정보학회논문지
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• 제11권2호
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• pp.79-85
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• 2006

휴대용 정보기기의 발달은 평판 디스플레이 장비 및 부품 소재의 수요급증으로 이어지고 있으며, 이 중에서 LCD는 LCD TV, 컴퓨터 모니터, 디지털 카메라, CNS(car navigation system), 게임기 등의 다양한 제품으로 그 응용범위가 폭넓어지고 있다. 이와 같이 LCD 시장이 급증함에 따라 LCD 배면조명 모듈인 BLU(backlight unit) 생산을 위한 제조업체들의 수도 크게 증가하였으며, 우수한 품질의 광학적 특성을 갖는 BLU 개발을 위해 광반사면 설계에 관한 연구가 꾸준히 진행되고 있다. 본 연구에서는 경험과 시행착오에 기초하여 수작업에 주로 의존하여 온 기존의 패턴설계환경을 개선하기 위해 CCFL을 광원으로 한 백라이트의 패턴 설계툴을 개발하였다. 본 연구의 검증을 위해 실모델의 백라이트에 대한 광반사면을 설계한 후, BM-7으로 휘도균일도를 측정하였다. 휘도균일도 측정결과, 본 연구의 설계툴을 사용한 BLU가 기존의 설계방식으로 보통 5회 이상의 시도에서 얻을 수 있는 휘도균일도를 1차 시도에서 얻을 수 있었다는 점에서 기존의 설계방식보다 우수한 설계 성능을 보임을 알 수 있었다.

• 제어로봇시스템학회논문지
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• 제12권10호
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• pp.968-974
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• 2006

We are moving into the era of ubiquitous computing. Ubiquitous Sensor Network (USN) is a base of such computing paradigm, where recognizing the identification and the position of objects is important. For the object identification, RFID tags are commonly used. For the object positioning, use of sensors such as laser and ultrasonic scanners is popular. Recently, there have been a few attempts to apply RFID technology in robot localization by replacing the sensors with RFID readers to achieve simpler and unified USN settings. However, RFID does not provide enough sensing accuracy for some USN applications such as robot navigation, mainly because of its inaccuracy in distance measurements. In this paper, we describe our approach on achieving accurate navigation using RFID. We solely rely on RFID mechanism for the localization by providing coordinate information through RFID tag installed floors. With the accurate positional information stored in the RFID tag, we complement coordinate errors accumulated during the wheel based robot navigation. We especially focus on how to distribute RFID tags (tag pattern) and how many to place (tag granularity) on the RFID tag-floor. To determine efficient tag granularities and tag patterns, we developed a simulation program. We define the error in navigation and use it to compare the effectiveness of the navigation. We analyze the simulation results to determine the efficient granularities and tag arrangement patterns that can improve the effectiveness of RFID navigation in general.

• 한국항해항만학회지
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• 제33권8호
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• pp.505-511
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• 2009

선박의 대형화에 따른 풍압면적의 증가 및 갑작스런 돌풍 등 자연환경의 급격한 변화 등으로 묘박 중인 선박이 주묘 되는 현상이 자주 발생되고 있다. 특히, 선박운항자의 관점에서는 풍속 및 파랑 등의 외력 변화에 따른 주묘 발생 시점 및 주묘 형태, 주묘시의 속력과 주변 선박 또는 장애물과의 충돌 가능성 등을 고려한 적절한 대응 방안이 모색되어야 한다. 본 논문은 실습선 한바다호가 단묘박으로 묘박 중 기상이 점점 악화되면서 실제로 주묘가 발생한 현상을 검토한 것으로, 묘박 당시의 풍압력, 유압력, 표류력, 선체운동 그리고 파주력 등을 분석하여 주묘의 발생 가능성 및 한계 외력을 고찰하였다. 또한, 당시의 외력 조건하에서 발생한 주묘패턴을 분석하여 선수방위 변화량, 스윙폭, 주묘 속도 등을 확인하였다.

• 제어로봇시스템학회논문지
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• 제7권5호
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• pp.454-464
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• 2001

In this paper, a personal navigation system is developed using GPS and dead reckoning sensors. This personal navigation system can be used to track a person inside a building, on an urban street, and in the mountain area. GPS can provide accurate absolute position information, but it cant be used without receiving enough satellite signals. Although the inertial sensors such as gyro an accelerometer and be used without this diggiculty, the inertial sensors severely suffer from their drift errors and the magne-tometer can be easily distorted by surrounding electromagnetic field. GPS and DR sensors can be inte-grated together to overcome these problems. A new personal navigation system that can be carried wit person is developed. A pedometer. actually vertically mounted accelerometer, detects ones footstep and gyro detects heading angle. These DR sensors are integrated with GPS and the humans walking pattern provides additional navigation information for compensating the DR sensors. The field testes are performed to evaluated the proposed navigation algorithm.

• Journal of Positioning, Navigation, and Timing
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• 제9권1호
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• pp.1-6
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• 2020

The Chinese BeiDou Satellite Navigation System consists of three kinds of constellations: the geostationary Earth orbit (GEO), the inclined geosynchronous satellite orbit (IGSO), and the medium Earth orbit (MEO). The BeiDou has expanded its service coverage from regional to global. Recently, the BeiDou has been widely used in ionospheric total electron content (TEC) research. In this study, we analyzed the BeiDou signals for ionospheric TEC monitoring over Jeju Island in South Korea. The BeiDou GEO TEC showed a clear pattern of diurnal variations. In addition, we compared the TEC values from the BeiDou GEO, the BeiDou IGSO, GPS, and International GNSS Service (IGS) Global Ionosphere Maps (GIM). There was a difference of about 5 TEC units between the BeiDou GEO and the IGS GIM. This may be due to the altitude difference between the different navigation satellites.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.333-335
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• 2006

Position of surface objects can be fixed in many ways. The most popular radionavigational systems, including satellite systems, make possible obtaining nearly continuous and very precise ship's position. However, under the water application of radionavigational systems is impossible. Underwater navigation requires other tools and solutions then these encountered in surface and air navigation. In underwater environment vehicles and submarines, operate that have to possess alternative navigational systems. Underwater vehicles, in order to perform their tasks require accurate information about their own, current position. At present, they are equipped with inertial navigational systems (INS). Accuracy of INS is very high but in relatively short periods. Position error is directly proportional to time of working of the system. The basic feature of INS is its autonomy and passivity. This characteristic mainly decides that INS is broadly used on submarines and other underwater vehicles. However, due to previously mentioned shortcoming i.e. gradually increasing position error, periodical calibration of the system is necessary. The simplest calibration method is surface or nearly surface application of GPS system. Another solution, which does not require interruption of performed task and emergence on the surface, is application of comparative navigation technique. Information about surrounding environment of the ship, obtained e.g. by means sonic depth finder or board sonar, and comparing it with accessible pattern can be used in order to fix ship's position. The article presents a structure and a description of working of underwater vehicle navigation system simulator. The simulator works on the basis of comparative navigation methods which exploit in turn digital images of echograms and sonograms. The additional option of the simulator is ability to robust estimation of measurements. One can do it in order to increase accuracy of position fixed with comparative navigation methods application. The simulator can be a basis to build future underwater navigation system.

• 한국항행학회논문지
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• 제23권6호
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• pp.526-534
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• 2019

전파 신호를 이용한 위치 추정 방법은 3개 이상의 앵커로부터 거리 측정치를 획득하여야 한다. 하지만 일반적인 건물은 좁고 기다란 복도와 모퉁이로 구성되어 있어 3개 이상의 가시 앵커를 확보하기 쉽지 않으며, 이로 인해 멀티 모달 솔루션이 발생하여 사용자의 위치를 추정하기가 어렵다. 이러한 문제를 극복하기 위해 본 논문에서는 인공신경망을 이용하여 위치를 추정하는 방법을 제안한다. 인공신경망을 이용하면 멀티 모달 솔루션이 발생하더라도 축적된 거리 측정치를 기반으로 사용자 이동 패턴 정보를 획득하여 위치를 추정할 수 있다. 해당 방법은 추가적인 장비나 센서가 필요치 않으며 오직 앵커 기반의 거리 측정치만으로 위치를 추정할 수 있다. 제안된 방법을 검증하기 위해 건물 내에 충분하지 않은 수의 앵커를 설치하여 멀티 모달 솔루션을 발생시킨 상황에서 위치 추정 테스트를 수행하였다. 그 결과 앵커의 수가 충분치 않은 상황에서도 위치를 추정할 수 있음을 확인하였다.

• Journal of Positioning, Navigation, and Timing
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• 제9권3호
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• pp.183-189
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• 2020

In emergency rescue situations, the localization accuracy of the rescue requestor is a very important factor in determining the success or failure of the rescue. Indoors where Global Navigation Satellite System (GNSS) is not operated, there is no choice but to use Wi-Fi or LTE signals. However, the performance of the current emergency rescue system utilizing those RF signals is exceedingly low. In this study, the effectiveness of the surface correlation technology using the accumulated signal pattern of RF signals was verified in relation to the emergency localization technology. To validate the proposed system, we configured and tested an emergency rescue scenario in multi-floors building. When the emergency rescue was requested, it was confirmed that the initial localization error was large owing to the short length of the accumulated signal pattern. However, the localization error decreased over time, which eventually led to the accurate location information being delivered to the rescuer.

• Journal of Positioning, Navigation, and Timing
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• 제6권2호
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• pp.43-51
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• 2017

In this study, the effect of the steering vector model mismatch due to array uncertainties on the performance of array processing was analyzed through simulation, along with the alleviation of the model mismatch effect depending on array calibration. To increase the reliability of the simulation results, the actual steering vector of the array antenna obtained by electromagnetic simulation was used along with the Jahn's channel model, which is an experimental channel model. Based on the analysis of the power spectrum for each direction, beam pattern, and the signal-to-interference-plus-noise ratio of the beamformer output, the performance deterioration of array processing due to array uncertainties was examined, and the performance improvement of array processing through array calibration was also examined.

• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.466-479
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• 2006

This paper addresses a formation navigation issue for a group of mobile robots passing through an environment with either static or moving obstacles meanwhile keeping a fixed formation shape. Based on Lyapunov function and graph theory, a NN formation control is proposed, which guarantees to maintain a formation if the formation pattern is $C^k,\;k\geq1$. In the process of navigation, the leader can generate a proper trajectory to lead formation and avoid moving obstacles according to the obtained information. An evolutionary computational technique using particle swarm optimization (PSO) is proposed for motion planning so that the formation is kept as $C^1$ function. The simulation results demonstrate that this algorithm is effective and the experimental studies validate the formation ability of the multiple mobile robots system.