• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.2
• /
• pp.72-78
• /
• 2011

Localization information of an object can be a very useful element for many application areas. Presently, GPS is typically used for it, but many researches on the wireless localization technology are going on recently actively using mobile communication network, wireless sensor network, and ad hoc network in order to overcome the limitations of the GPS such as indoor, cost, power consumption, and etc. Therefore, this article surveys the most representative wireless localization techniques, which can be deployed in the wireless networks, and their principles and performances are analyzed based on the researched papers. In a conclusion, selection of a localization technique should consider the key design elements to a given application from the design elements such as localization environment, accuracy, time to fix, computation amount, implementation ease, and etc.

• Proceedings of the KSRS Conference
• /
• 2007.03a
• /
• pp.277-282
• /
• 2007

유비쿼터스 시대가 도래함에 따라 실외에서 뿐만 아니라 실내에서 대상물의 위치를 결정하기 위한 기술의 필요성이 증가하고 있다. 실외에서는 GPS를 이용하여 광범위한 지역에 안정적인 서비스를 제공받을 수 있지만 건물 인근 지역에서는 위치결정에 필요한 수의 위성이 확보되지 않고， 다중경로 오차의 영향 등으로 위치결정이 불가능하고 실내에서 활용 가능한 수준의 위치 정보를 제공하는 것이 어렵다는 단점이 있다. 실내 위치 결정을 위한 다양한 방법 중에 RFID를 이용한 방법은 GPS 에 비해 위치 정확도는 낮지만 실내에서 비교적 적은 비용으로 위치 결정이 가능하므로 GPS로 위치 결정이 불가능한 지역에 시스템을 구축하면 설내/외에서 연속적인 위치결정이 가능하게 된다. 연속적 위치 결정을 위해 GPS 신호 수신이 가능한 실외 지역에서 RFID 시스템을 설치한 건물 안으로 이동하면서 수신된 데이터를 이용하여 실내외에서의 연속적인 위치결정을 수행하였다. 특히，데이터 에포크 간의 거리를 통해 이상점을 탐지하고, 이상점(Outlier)이 발생할 경우 다른 센서로 위치결정을 대체하는 기법을 제안하였고 그 결과 실내외에서 연속적인 위치결정이 가능함을 확인할 수 있었다.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.7
• /
• pp.627-633
• /
• 2015

Accurate heading information is crucial for the navigation of intelligent vehicles. In outdoor environments, GPS is usually used for the navigation of vehicles. However, in GPS-denied environments such as dense building areas, tunnels, underground areas and indoor environments, non-GPS solutions are required. Yaw-rates from a single gyro sensor could be one of the solutions. In dealing with gyro sensors, the drift problem should be resolved. HDR (Heuristic Drift Reduction) can reduce the average heading error in straight line movement. However, it shows rather large errors in some moving environments, especially along curved lines. This paper presents a method called VDR (Vision-based Drift Reduction), a system which uses a low-cost vision sensor as compensation for HDR errors.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2010.11a
• /
• pp.1384-1387
• /
• 2010

최근 무선인터넷의 기술을 이용한 스마트폰의 활용도가 높아짐에 따라 새로운 서비스의 연구분야로 단말기를 이용하여 이동객체의 위치정보를 제공받는 위치 기반 서비스 기술에 관심이 높아지고 있다. 하지만 현재 기술은 GPS를 이용한 위치추적으로 외부의 이동객체를 추적하는 기술로 많이 활용되고 있다. 그리고 고정된 레퍼런스 노드 또는 마스터 노드에 의존하고 있는 문제점과 위치 계산을 위한 기준이 대부분 홉스나 RF신호의 수신강도에 의한 거리차를 이용하는데 전파 특성에 따른 회절 및 반사, 다중 경로 등에 의한 신호감쇠현상으로 정확도를 보장하지 못하는 문제점이 있다. 따라서 본 논문에서는 GPS와 WiFi를 이용하여 고정된 레퍼런스 노드에 의존하지 않고 이동식 GPS-AP를 이용하여 건물내부에 위치하는 특정 단말기의 위치정보를 제공할 수 있는 시스템을 제안한다.

• IE interfaces
• /
• v.25 no.1
• /
• pp.114-126
• /
• 2012

This study describes a real-time location monitoring system developed for efficient operation of workplace in plant equipment maker. This monitoring system can be applied for indoor and outdoor working environment respectively. By using the real-time tracking system based on RTLS, it is possible to track worker's movement and location of working object under indoor working environment. For outdoor working environment, the real-time monitoring system based on IDGPS is applied for work safety and balanced workload. A case study is provided to evaluate the performance of the real-time monitoring system.

• International Journal of Contents
• /
• v.5 no.2
• /
• pp.59-63
• /
• 2009

Since it is hard to use GPS for tracking mobile user in indoor environments, much research has focused on techniques using existing wireless local area network infrastructure. Signal strength received at a fixed location is not constant, so fingerprinting approach which use pattern matching is popular. But this approach has to pay additional costs to determine user location. This paper proposes a new approach to find user's location efficiently using an index scheme. After analyzing characteristics of RF signals, the paper suggests the data processing method how the signal strength values for each of the access points are recorded in a radio map. To reduce computational cost during the location determination phase, multidimensional indexes for radio map with the important information which is the order of the strongest access points are used.

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.187-189
• /
• 2009

Position estimation in indoor is significant problem, because GPS which is usually used for outdoor positioning cannot be utilized to indoor positioning. Sensor network can be a solution for the positioning. Recently, chirp spread spectrum(CSS) specified in IEEE 802.15.4a provides an ability of ranging. Based on the results of the ranging, a position of a CSS node can be calculated by using trilateration. In this case, Kalman filter can be applied to the trilateration because of the measurement noise. In this paper, we apply the unscented Kalman filter for the trilateration. The trilateration can be represented to a nonlinear state space equation, and the unscented Kalman filter is suitable for nonlinear state space equation. Through the experimental results. we show the accuracy of the estimated position.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.6
• /
• pp.529-536
• /
• 2004

Autonomous navigation of an indoor mobile robot using the global ultrasonic system is presented in this paper. Since the trajectory error of the dead-reckoning navigation grows with time and distance, the autonomous navigation of a mobile robot requires to localize the current position of the robot, so that to compensate the trajectory error. The global ultrasonic system consisting of four ultrasonic generators fixed at a priori known positions in the work space and two receivers on the mobile robot has the similar structure with the well-known satellite GPS(Global Positioning System), and it is useful for the self-localization of an indoor mobile robot. The EKF(Extended Kalman Filter) algorithm for the self-localization is proposed and the autonomous navigation based on the self-localization is verified by experiments.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.9
• /
• pp.925-930
• /
• 2008

Many sensor network applications require that each node's sensor data stream be annotated with its physical location in some coordinate system. Equipping GPS on every sensor node is often expensive and does not work in indoor deployments. Recently, cricket-based localization system is often used for indoor localization system. It is very important to know the exact position of beacons in cricket-based localization system for identifying moving sensor node's position. In this paper, a new method, Mobile Listener Detect Algorithm (MLD) which can automatically calculate the unknown newly installed beacons is proposed. For the verification of the feasibility of the proposed scheme, we have conducted several experiments.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2012.01a
• /
• pp.227-228
• /
• 2012

실외에서의 위치추적은 GPS(Global Positioning System) 등의 다양한 방법이 활용가능하다. 하지만 실내에서는 사용이 어려워 비전, RFID 및 Zigbee 등을 활용한 다양한 연구가 진행되고 있다. 본 연구에서는 비교적 비용 효과적으로 구축이 가능한 수동형 RFID 태그를 기반 이동형 로봇의 위치 추적 알고리즘을 제안하도록 한다. 총 7 종의 태그에 대하여 각 태그가 가지고 있는 특성을 실험을 통하여 분석하고 분석한 결과에 따라 태그를 배치하여 효과적으로 로봇의 이동에 따른 위치 추적 및 이동방향 예측방법을 기술한다. 제안하는 방법을 실험실 환경에서 레고 마인드스톰을 활용하여 그 효용성을 나타내도록 한다.