• 제어로봇시스템학회논문지
• /
• 제12권9호
• /
• pp.876-882
• /
• 2006

This study presents an ultrasonic location awareness system for the ubiquitous computing with absolute position. The flight time of ultrasonic waves is determined by a period detecting technique which is able to extend the sensing range compared with traditional methods. For location awareness, ultrasonic waves are sent successively from each ultrasonic transmitter and synchronized by radio frequency (RF) signal, where the transmitting part is fixed and the receiving part is movable. To expand the recognizing range, cell matching technique and coded ultrasonic technique are introduced. The experimentation for various distances is accomplished to verify the used period detecting technique of U-SAT system. The positioning accuracy by using cell matching is also verified by finding the locations of settled points and the usability of coded ultrasonic technique is verified. As a result, the possibility of ultrasonic location awareness system for the ubiquitous computing can be discussed as a pseudo-satellite system with low cost, a high update rate, and relatively high precision, in the places where CPS is not available.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권5호
• /
• pp.1339-1355
• /
• 2023

Localization is a hot research spot for many areas, especially in the mobile robot field. Due to the weak signal of the global positioning system (GPS), the alternative schemes in an indoor environment include wireless signal transmitting and receiving solutions, laser rangefinder to build a map followed by a re-localization stage and visual positioning methods, etc. Among all wireless signal positioning techniques, Wi-Fi is the most common one. Wi-Fi access points are installed in most indoor areas of human activities, and smart devices equipped with Wi-Fi modules can be seen everywhere. However, the localization of a mobile robot using a Wi-Fi scheme usually lacks orientation information. Besides, the distance error is large because of indoor signal interference. Another research direction that mainly refers to laser sensors is to actively detect the environment and achieve positioning. An occupancy grid map is built by using the simultaneous localization and mapping (SLAM) method when the mobile robot enters the indoor environment for the first time. When the robot enters the environment again, it can localize itself according to the known map. Nevertheless, this scheme only works effectively based on the prerequisite that those areas have salient geometrical features. If the areas have similar scanning structures, such as a long corridor or similar rooms, the traditional methods always fail. To address the weakness of the above two methods, this work proposes a coarse-to-fine paradigm and an improved localization algorithm that utilizes Wi-Fi to assist the robot localization in a geometrically similar environment. Firstly, a grid map is built by using laser SLAM. Secondly, a fingerprint database is built in the offline phase. Then, the RSSI values are achieved in the localization stage to get a coarse localization. Finally, an improved particle filter method based on the Wi-Fi signal values is proposed to realize a fine localization. Experimental results show that our approach is effective and robust for both global localization and the kidnapped robot problem. The localization success rate reaches 97.33%, while the traditional method always fails.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권2호
• /
• pp.187-194
• /
• 2015

Accurate relative location estimation is a key requirement in indoor localization systems based on wireless sensor networks (WSNs). However, although these systems have applied not only various optimization algorithms but also fusion with sensors to achieve high accuracy in position determination, they are difficult to provide accurate relative azimuth and locations to users because of cumulative errors in inertial sensors with time and the influence of external magnetic fields. This paper based on ultra-wideband positioning system, which is relatively suitable for indoor localization compared to other wireless communications, presents an indoor localization system for estimating relative azimuth and location of location-unaware nodes, referred to as target nodes without applying any algorithms with complex variable and constraints to achieve high accuracy. In the proposed method, the target nodes comprising three mobile nodes estimate the relative distance and azimuth from two reference nodes that can be installed by users. In addition, in the process of estimating the relative localization information acquired from the reference nodes, positioning errors are minimized through a novel modified rounding estimation technique in which Kalman filter is applied without any time consumption algorithms. Experimental results show the feasibility and validity of the proposed system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권1호
• /
• pp.343-364
• /
• 2021

In the 5G era, the communication networks tend to be ultra-densified, which will improve the accuracy of indoor positioning and further improve the quality of positioning service. In this study, we propose an indoor three-dimensional (3D) dynamic reconstruction fingerprint matching algorithm (DSR-FP) in a 5G ultra-dense network. The first step of the algorithm is to construct a local fingerprint matrix having low-rank characteristics using partial fingerprint data, and then reconstruct the local matrix as a complete fingerprint library using the FPCA reconstruction algorithm. In the second step of the algorithm, a dynamic base station matching strategy is used to screen out the best quality service base stations and multiple sub-optimal service base stations. Then, the fingerprints of the other base station numbers are eliminated from the fingerprint database to simplify the fingerprint database. Finally, the 3D estimated coordinates of the point to be located are obtained through the K-nearest neighbor matching algorithm. The analysis of the simulation results demonstrates that the average relative error between the reconstructed fingerprint database by the DSR-FP algorithm and the original fingerprint database is 1.21%, indicating that the accuracy of the reconstruction fingerprint database is high, and the influence of the location error can be ignored. The positioning error of the DSR-FP algorithm is less than 0.31 m. Furthermore, at the same signal-to-noise ratio, the positioning error of the DSR-FP algorithm is lesser than that of the traditional fingerprint matching algorithm, while its positioning accuracy is higher.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제6권3호
• /
• pp.794-814
• /
• 2012

We propose a novel method for improving Wi-Fi positioning accuracy while reducing the energy consumption of mobile devices. Our method presents three contributions. First, we jointly and intelligently select the optimal subset of access points for positioning via maximum mutual information criterion. Second, we further propose local discriminant embedding algorithm for nonlinear discriminative feature extraction, a process that cannot be effectively handled by existing linear techniques. Third, to reduce complexity and make input signal space more compact, we incorporate clustering analysis to localize the positioning model. Experiments in realistic environments demonstrate that the proposed method can lower energy consumption while achieving higher accuracy compared with previous methods. The improvement can be attributed to the capability of our method to extract the most discriminative features for positioning as well as require smaller computation cost and shorter sensing time.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2022년도 춘계학술대회
• /
• pp.89-91
• /
• 2022

실내에서 측위를 위해 주로 사용되는 무선 센서 네트워크(WSN)는 수신 신호 강도(RSSI)의 정확성에 의존한다. 이 RSSI는 간섭을 유발하는 여러 요인에 민감하며, 그 중 온도가 실내/외 환경에서 RSSI에 큰 영향을 미친다는 국외 연구 사례가 있다. 실내에서는 열원이나 공조 시스템으로 인해 실내 공간의 온도가 고르지 않으며, 특정 위치에서는 잦은 온도 변화가 발생한다. 특히, 실내 화재 상황 시 대피 경로 안내를 위해 정확한 측위 시스템이 요구되지만 Receiver 주변에서의 화재로 인해 국부적으로 높은 온도가 형성되어 RSSI 값에 영향을 미칠 수 있다. 본 논문에서는 SoC 내부 및 국부 온도와 RSSI의 상관관계 분석을 통해 RSSI에 미치는 영향을 연구하고자 한다.

• 제어로봇시스템학회논문지
• /
• 제21권5호
• /
• pp.490-495
• /
• 2015

As flying robots are becoming popular, there are increased needs to use themforsuch purposes as parcel delivery, serving in restaurants, and stage performances. To control flying robots such as quad copters, localization is essential. In order to properly position flying robots, many techniques are in development, including IR (infra-red)-based systemswhich catch markers on a flying robot in order that it can position itself. However, this technique demonstrates only short coverage. Furthermore, localization from inertial sensors diverges as time passes. For this reason, this paper suggests a TWR (two-way ranging) based positioning technique. Despite the weaknesses in currently available TWR system, this paper suggests a self-positioning and outlier detection technique in order to provide reliable position information with a faster update rate. The self-positioning system sends a shorter message which reduces wireless traffic. By detecting and removing outlier measurements, a positioning result with better accuracy is acquired. Finally, this paper shows that the suggesting system detects outlierssequentially from less than half the number of anchors in localization system according to the degree of outlier in measurement and the noise level. By performing an outlier algorithm, better positioning accuracy is acquired as shown in the experimental result.

• 제어로봇시스템학회논문지
• /
• 제13권6호
• /
• pp.603-608
• /
• 2007

In the conventional AOA(angle-of-arrival) positioning utilizing reverse-link wireless channel, each sensor should be equipped with an array antenna to measure the incident angle of signal transmitting from a tag. To perform the complicated signal processing for angle measurements, sensor size and its power consumption will be large. In some applications like mobile robot location, there exists no strict restriction in tag size or in power consumption. Rather, it is desirable that the sensor would be as small as possible. This paper presents a new AOA positioning method utilizing forward-link channel. Under the assumption that the mobile robot is operating on the flat surface, the measurement model for FLAOA(tiJrward-link AOA) is derived first. Two kinds of position estimation algorithms using FLAOA measurements are proposed; Gauss-Newton method and closed-fonn solution method. With the proposed methods, we can ohtain the attitude of robot as well as its position. Positioning performance of proposed methods is compared by computer simulation. Simulation results show that the closed-form solution method using FLAOA measurements is suitable for indoor robot positioning.

• 한국통신학회논문지
• /
• 제42권2호
• /
• pp.413-423
• /
• 2017

본 논문은 실내에서 위치를 측정하기 위해 초음파와 RF 기반의 실내 측위 시스템을 제안한다. 기존의 실내 측위 방안은 시간 동기화, 시스템의 복잡도, 측위의 정확성 등의 문제가 있다. 이러한 문제를 해결하기 위해 초음파와 무선주파수(RF)를 이용한 송수신 시스템을 제안한다. 송신시스템은 한 쌍의 초음파 송신기와 RF 송신기로 구성하고, 수신시스템은 복수의 초음파 수신기들과 하나의 RF 수신기로 구성한다. 또한, 제안된 시스템이 가질 수 있는 성능의 한계를 수학적으로 분석하였다. 제안된 시스템은 시뮬레이션뿐만 아니라 아두이노 모듈을 이용하여 실제 시스템을 제작하여 측위 성능을 평가하였다. 실내 공간 $2m{\times}2m{\times}2m$에서 25개 지점의 위치를 측정한 결과, 평균 6.1cm, 표준편차 1.6cm의 성능을 보였다.

• 한국재난정보학회 논문집
• /
• 제12권2호
• /
• pp.130-135
• /
• 2016

본 논문은 재난 상황 발생 시 승객 및 대피자에게 안전하게 대피 경로를 제공하는 동향 분석에 관한 연구이다. 동향 분석을 위해 국내외 논문과 국내특허를 주로 살펴보았으며, 최근 15년 이내의 국내외 논문 31편, 국내 특허 29건, 논문을 통한 기 수행된 국가과제 9건을 분석하였다. 분석 결과 기존의 연구는 대피 유도 시스템 중심으로 수행되었으며, 대피자 관점에서 실제로 활용될 수 있는 수준의 실내 재난 대피 기술에 대한 연구는 전무한 것으로 나타났다. 이는 실내 공간에서 위치인식 기술의 부재 또는 한계점이 있는 것으로 파악되었고 이를 해소하기 위해 기술로 본 논문에서는 실내 위치인식기술의 활용을 제안하였다. 실내 재난 상황을 고려한 새로운 시스템 연구 및 개발의 기초 자료로 활용될 수 있을 것으로 기대된다.