• ETRI Journal
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• 제35권3호
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• pp.361-370
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• 2013

In this paper, a packet-reduced ranging method using a superresolution time of arrival estimation algorithm for a chirp-based real-time locating system is presented. A variety of ranging methods, such as symmetric double-sided two-way ranging (SDS-TWR), have been proposed to remove the time drift due to the frequency offset using extra ranging packets. Our proposed method can perform robust ranging against the frequency offset using only two ranging packets while maintaining almost the same ranging accuracy as them. To verify the effectiveness of our proposed algorithm, the error performance of our proposed ranging method is analyzed and compared with others. The total ranging performance of TWR, SDS-TWR, and our proposed TWR are analyzed and verified through simulations in additive white Gaussian noise and multipath channels in the presence of the frequency offset.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.376-382
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• 2010

We propose a novel method to precisely detect car license plates by locating main characters, which are printed with large font size. The regions of the main characters are directly detected without detecting the plate region boundaries, so that license regions can be detected more precisely than by other existing methods. To generate a binary image, multiple thresholds are applied, and segmented regions are selected from multiple binarized images by a criterion of size and compactness. We do not employ any character matching methods, so that many candidates for main character groups are detected; thus, we use a neural network to reject non-main character groups from the candidates. The relation of the character regions and the intensity statistics are used as the input to the neural network for classification. The detection performance has been investigated on real images captured under various illumination conditions for 1000 vehicles. 980 plates were correctly detected, and almost all non-detected plates were so stained that their characters could not be isolated for character recognition. In addition, the processing time is fast enough for a commercial automatic license plate recognition system. Therefore, the proposed method can be used for recognition systems with high performance and fast processing.

• 한국건축시공학회지
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• 제9권1호
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• pp.95-101
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• 2009

Although the concept of RTLS is very unfamiliar to construction industry, recently it is popular in other industry, such as logistics, ship building, mobile telecommunication based on state-of-the-art information technology. Effective resource management using cutting-edge information technology makes it possible to succeed a project with saving the time and cost. And effective information management in construction project can be achieved by the new technologies such as RFID, WEB-based internet, DB technology, real-time monitoring technology, etc. This paper suggest the characteristics and applicability of the international standard electric waves to be used for the real-time locating system (RTLS) on the viewpoint of transmission loss in construction field to monitor and manage resources of construction project effectively The two types of electric waves based on the international standard is to be suggested after surveying the as-is technology in the related industries and then is analyzed to find out the characteristics of those by the concept of the electric wave transition loss in the several construction situations. Two main electric waves, the 2.4GHz and the 433MHz technologies as the international standard is researched on the applicability to the indoor environment of construction site.

• 정보처리학회논문지A
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• 제19A권2호
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• pp.85-92
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• 2012

본 논문에서는 다수의 고속 이동체들의 위치를 측정할 수 있는 확장성 있는 실시간 위치 측정 시스템을 제안한다. 제안된 시스템에서는 위치 서비스가 필요한 영역을 확장 시 기본 단위인 매크로셀이라고 불리는 정사각형의 격자들로 나누고, 한 매크로셀은 $N{\times}N$ 개의 마이크로셀로 나눈다. 마이크로셀의 각 꼭짓점에는 위치 기준 노드가 중앙에는 중재 노드가 설치된다. 위치를 측정하고자 하는 이동체는 우선 중재 노드와의 통신을 통하여 위치 측정을 위한 허가를 받아야 한다. 그러므로 한 마이크로셀내에서는 오직 허가된 하나의 이동 노드만이 위치 기준 노드들과 연속적으로 통신하면서 자신의 위치를 계산할 수 있다. 제안된 시스템의 성능을 측정하기 위하여, 제안된 시스템을 모델링하고 시뮬레이션 하였다. 시뮬레이션 결과 제안된 시스템은 위치 측정을 위한 통신 시간이 짧고 고속 이동체의 위치를 계산할 경우 오차가 적은 것으로 나타났다.

• 한국통신학회논문지
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• 제37C권9호
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• pp.763-773
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• 2012

본 논문에서는 Wi-Fi를 이용한 RSSI (Received Signal Strength Indication)기반의 측위 시스템에서 전파환경변화에 민감한 시스템의 문제를 보완하기 위하여 랜드마크 발신기 기반의 측위 시스템을 제안한다. 이를 위하여 핑거프린팅 알고리즘 및 랜드마크 발신기를 구현 하였으며 간단한 측위 정확도 예측모델을 만들어 수신된 전파세기를 기반으로 측위 정확도를 예측하였다. 이를 바탕으로 실내 TEST BED를 구축하였고 주요 지점에 랜드마크 발신기를 부착하여 시스템의 효용성을 검증하였다.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2007년도 GIS 공동춘계학술대회 논문집
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• pp.15-20
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• 2007

최근 항만 물류 및 자산 관리 분야에서 실시간 위치 정보를 처리하는 RTLS(Real Time Locating System)시스템이 도입되고 있다. 이러한 시스템에서 RTLS 서버는 태그를 부착한 이동 객체들의 위치 데이터 스트림을 일정 시간 동안 수집하여 애플리케이션으로 전달한다. 이 때 위치 정보는 전파 굴절 현상으로 인해 오차가 발생하며, 이동 객체에 부착된 태그는 수 초 마다 위치 정보를 보고하기 때문에 시스템의 과부하를 초래하게 된다. 본 논문에서는 표준과의 호환성을 고려하고, 요구사항을 반영한 위치 데이터 스트림 처리기를 설계 및 개발하였다. RTLS 시스템의 전파 굴절 현상으로 야기되는 비정상적인 위치 오차를 보정하기 위해 맵 매칭 기법을 도입하여 위치 데이터 스트림의 신뢰성을 제공하며, 위치 변화가 없는 객체의 위치 데이터 스트림을 빠르게 정제하는 정지 상태 제거 필터를 개발하여 질의 처리 시 부하를 줄인다. 또한 각 애플리케이션의 질의 결과에 무의미한 위치 정보를 배제하는 중요 위치 수집기를 개발하여 시스템 성능을 향상시킨다.

• 대한임베디드공학회논문지
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• 제6권1호
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• pp.8-15
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• 2011

This paper presents an effective method for detecting vehicles in front of the camera-assisted car during nighttime driving. The proposed method detects vehicles based on detecting vehicle headlights and taillights using techniques of image segmentation and clustering. First, in order to effectively extract spotlight of interest, a pre-signal-processing process based on camera lens filter and labeling method is applied on road-scene images. Second, to spatial clustering vehicle of detecting lamps, a grouping process use light tracking method and locating vehicle lighting patterns. For simulation, we are implemented through Da-vinci 7437 DSP board with visible light mono-camera and tested it in urban and rural roads. Through the test, classification performances are above 89% of precision rate and 94% of recall rate evaluated on real-time environment.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.510-519
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• 2020

Within an intelligent automated cyber-physical system, the realization of the autonomous mechanism for data collection, data integration, and data analysis plays a critical role in the design, development, operation, and maintenance of such a system. This construct is particularly vital for fault-tolerant route-finding systems that rely on the imprecise GPS location of the vehicles to properly operate, timely plan, and continuously produce informative feedback to the user. More essentially, the integration of digital twins with cyber-physical route-finding systems has been overlooked in intelligent transportation services with the capacity to construct the network routes solely from the locations of the operating vehicles. To address this limitation, the present study proposes a conceptual architecture that employs digital twin to autonomously maintain, update, and manage intelligent transportation systems. This virtual management simulation can improve the accuracy of time-of-arrival prediction based on auto-generated routes on which the vehicle's real-time location is mapped. To that end, first, an intelligent transportation system was developed based on two primary mechanisms: 1) an automated route finding process in which predictive data-driven models (i.e., regularized least-squares regression) can elicit the geometry and direction of the routes of the transportation network from the cloud of geotagged data points of the operating vehicles and 2) an intelligent mapping process capable of accurately locating the vehicles on the map whereby their arrival times to any point on the route can be estimated. Afterward, the digital representations of the physical entities (i.e., vehicles and routes) were simulated based on the auto-generated routes and the vehicles' locations in near-real-time. Finally, the feasibility and usability of the presented conceptual framework were evaluated through the comparison between the primary characteristics of the physical entities with their digital representations. The proposed architecture can be used by the vehicle-tracking applications dependent on geotagged data for digital mapping and location tracking of vehicles under a systematic comparison and simulation cyber-physical system.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.776-785
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• 2011

Since the Internet-based real-time Global Positioning System(GPS) synchronized widearea power system frequency monitoring network (FNET) was proposed in 2001, it has been monitoring the power system frequency in interconnected United States power systems and numerous interesting behaviors have been observed, including frequency excursion propagation. We address the consistency of a frequency excursion detection order of frequency disturbance recorders in FNET in relation to the same generation trip, as well as the ability to recreate by power systems dynamic simulation. We also propose a new method, as an application of FNET measurement, to locate a tripped generator using power systems dynamic simulation and wide-area frequency measurement. The simulation database of all the possible trips of generators in the interconnected power systems is created using the off-line power systems dynamic simulation. When FNET detects a sudden drop in the monitoring frequency, which is most likely due to a generation trip in power systems, the proposed algorithm locates a tripped generator by finding the best matching case of the measured frequency excursion in the simulation database in terms of the frequency drop detection order and the time of monitoring points.

• 한국ITS학회 논문지
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• 제19권6호
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• pp.61-73
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• 2020

IoT 디바이스로부터 수집된 위치정보를 활용한 실시간 위치센싱 기술은 항만 등 다양한 산업현장에서 활용되고 있다. 그러나 GPS 센서의 특성상 오차는 항상 존재하며, 이를 활용하는 사고위험 검지 알고리즘은 오차의 고려가 필수적이다. 본 연구는 GPS 오차를 고려한 항만 내 낙하물 사고위험 구역 접근검지 알고리즘의 보정 방법론을 제안한다. IoT 디바이스로부터 수집된 GPS 오차 데이터를 확률변수로 하는 확률밀도함수를 추정하였으며 알고리즘의 검증을 위해 미시적 시뮬레이션을 활용하였다. 검증 결과 알고리즘은 디바이스의 위치오차 1m, 5m에 따라 검지 정확도가 각각 93%, 77%로 나타났다. 본 연구는 향후 디바이스의 성능을 고려한 유효 위험범위 설정 및 안전관리에 중요한 역할을 할 수 있을 것으로 기대된다.