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Localization using Magnetometers and Light Sensors
Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Localization is essential in a variety of applications such as navigation systems, aerospace and surface surveillance, robotics and animal migration studies to mention a few. There are many standard techniques available, where the most common are based on information from satellite or terrestrial radio beacons, radar networks or vision systems.

In this thesis, two alternative techniques are investigated.The first localization technique is based on one or more magnetometers measuring the induced magnetic field from a magnetic object. These measurements depend on the position and the magnetic signature of the object and can be described with models derived from the electromagnetic theory. For this technology, two applications have been analyzed. The first application is traffic surveillance, which has a high need for robust localization systems. By deploying one or more magnetometer in the vicinity of the traffic lane, vehicles can be detected and classified. These systems can be used for safety purposes, such as detecting wrong-way drivers on highways, as well as for statistical purposes by monitoring the traffic flow.

The second application is indoor localization, where a mobile magnetometer measures the stationary magnetic field induced by magnetic structures in indoor environments. In this work, models for such magnetic environments are proposed and evaluated.The second localization technique uses light sensors measuring light intensity during day and night. After registering the time of sunrise and sunset from this data, basic formulas from astronomy can be used to locate the sensor. The main application is localization of small migrating animals. In this work, a framework for localizing migrating birds using light sensors is proposed. The framework has been evaluated on data from a common swift, which during a period of ten months was equipped with a light sensor.

Abstract [sv]

Förmågan att kunna bestämma var ett objekt befinner sig är viktigt inom många olika tillämpningar, till exempel inom flyg- och sjöbevakning, robotik och studier av djurs flyttvägar, för att nämna några.  Det är speciellt önskvärt att kunna utföra denna positionering utan mänsklig inblandning, antingen för att kunna positionerna objekt som en människa inte skulle klara av att göra, eller för att effektivisera arbetet. För att automatiskt bestämma en position behövs sensorer, som mäter olika saker i dess omgivning och omvandlar detta till en elektrisk signal. Med ett datorprogram kan denna elektriska signal i sin tur sedan omvandlas till en position. Det finns många standardteknologier tillgängliga som använder sig av olika typer av sensorer som mäter olika saker. De vanligaste är baserade på satelliternavigering (GPS), radiovågor, radar och kameror.  I denna avhandling har två alternativa teknologier undersökts som i vissa tillämpningar har olika fördelar gentemot standardteknologierna.Den första teknologin för att positionera ett objekt är baserad på en eller flera sensorer som känner av magnetfältet från objekt som innehåller mycket metall, till exempel fordon. Från detta magnetfält kan man bestämma position och även storlek på objektet. Med denna teknologi som grund har två tillämpningar analyserats.

Den första tillämpningen är trafikövervakning, där det finns ett stort behov av teknologi som kan bestämma position på bilar. Genom att placera ut en eller flera sensorer längs vägrenen kan man känna av bilar som kommer i närheten. Dessa system kan användas för säkerhetsändamål, som att varna för bilar som kör i fel riktning på motorvägar, eller för statistiska ändamål genom att övervaka trafikflödet. Den andra tillämpningen handlar om att bestämma position för ett objekt i en inomhusmiljö. I många byggnader finns det många objekt som innehåller metall. Dessa objekt omges av ett magnetfält. Genom att i en inomhusmiljö vandra runt med en sensor, så kommer den att känna av olika starka magnetfält beroende på var i byggnaden man befinner sig. I denna avhandling kommer vi undersöka matematiska modeller för att beskriva sådana magnetiska objekt.

Den andra teknologin använder ljussensorer för att studera till vilka områden som flyttfåglar flyger. Fågeln utrustas med en ljussensor som mäter ljusstyrka under hela dygnet. Därefter släpps fågeln iväg och förhoppningsvis hittar man den ett år senare igen så att all information från sensorn kan analyseras. Från dessa mätningar kan man i efterhand beräkna vid vilken tidpunkt som soluppgången och solnedgången har inträffat. Därefter kan fågels flyttväg bestämmas med hjälp av formler från astronomin. I detta arbete föreslås en metod för hur denna information kan analyseras. Metoden har utvärderats på data från en tornseglare som under en period på tio månader flyttat till Afrika och sedan tillbaka till Sverige igen.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 150 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1581
National Category
Signal Processing
Identifiers
URN: urn:nbn:se:liu:diva-88967Local ID: LIU-TEK-LIC-2013:15ISBN: 978-91-7519-663-3 (print)OAI: oai:DiVA.org:liu-88967DiVA: diva2:606554
Presentation
2013-03-13, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research
Available from: 2013-02-21 Created: 2013-02-19 Last updated: 2013-02-21Bibliographically approved
List of papers
1. Magnetometer Modeling and Validation for Tracking Metallic Targets
Open this publication in new window or tab >>Magnetometer Modeling and Validation for Tracking Metallic Targets
2014 (English)In: IEEE TRANSACTIONS ON SIGNAL PROCESSING, ISSN 1053-587X, Vol. 62, no 3, 545-556 p.Article in journal (Refereed) Published
Abstract [en]

With the electromagnetic theory as basis, we present a sensor model for three-axis magnetometers suitable for localization and tracking as required in intelligent transportation systems and security applications. The model depends on a physical magnetic dipole model of the target and its relative position to the sensor. Both point target and extended target models are provided as well as a target orientation dependent model. The suitability of magnetometers for tracking is analyzed in terms of local observability and the Cramér Rao lower bound as a function of the sensor positions in a two sensor scenario. The models are validated with real field test data taken from various road vehicles which indicate excellent localization as well as identification of the magnetic target model suitable for target classification. These sensor models can be combined with a standard motion model and a standard nonlinear filter to track metallic objects in a magnetometer network.

Place, publisher, year, edition, pages
IEEE Signal Processing Society, 2014
National Category
Signal Processing
Identifiers
urn:nbn:se:liu:diva-88963 (URN)10.1109/TSP.2013.2274639 (DOI)000330771300002 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2013-02-19 Created: 2013-02-19 Last updated: 2014-11-26Bibliographically approved
2. Classification of Driving Direction in Traffic Surveillance using Magnetometers
Open this publication in new window or tab >>Classification of Driving Direction in Traffic Surveillance using Magnetometers
2014 (English)In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 15, no 4, 1405-1418 p.Article in journal (Refereed) Published
Abstract [en]

We present an approach for computing the driving direction of a vehicle by processing measurements from one 2-axis magnetometer. The proposed method relies on a non-linear transformation of the measurement data comprising only two inner products. Deterministic analysis of the signal model reveals how the driving direction affects the measurement signal and the proposed classifier is analyzed in terms of its statistical properties. The method is compared with a model based likelihood test using both simulated and experimental data. The experimental verification indicates that good performance is achieved under the presence of saturation, measurement noise, and near field effects.

Place, publisher, year, edition, pages
IEEE Press, 2014
National Category
Signal Processing
Identifiers
urn:nbn:se:liu:diva-88965 (URN)10.1109/TITS.2014.2298199 (DOI)000340627700003 ()
Funder
Swedish Foundation for Strategic Research VINNOVA
Available from: 2013-02-19 Created: 2013-02-19 Last updated: 2017-12-06Bibliographically approved
3. Modeling Magnetic Fields using Gaussian Processes
Open this publication in new window or tab >>Modeling Magnetic Fields using Gaussian Processes
2013 (English)In: IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2013, IEEE conference proceedings, 2013, 3522-3526 p.Conference paper, Published paper (Refereed)
Abstract [en]

Starting from the electromagnetic theory, we derive a Bayesian nonparametric model allowing for joint estimation of the magnetic field and the magnetic sources in complex environments. The model is a Gaussian process which exploits the divergence- and curl-free properties of the magnetic field by combining well-known model components in a novel manner. The model is estimated using magnetometer measurements and spatial information implicitly provided by the sensor. The model and the associated estimator are validated on both simulated and real world experimental data producing Bayesian nonparametric maps of magnetized objects.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013
Series
IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2013, ISSN 1520-6149
National Category
Signal Processing
Identifiers
urn:nbn:se:liu:diva-88966 (URN)10.1109/ICASSP.2013.6638313 (DOI)000329611503136 ()978-1-4799-0356-6 (ISBN)
Conference
2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), May 26-31, Vancouver, Canada
Funder
Swedish Foundation for Strategic Research EU, FP7, Seventh Framework Programme
Available from: 2013-02-19 Created: 2013-02-19 Last updated: 2015-11-03Bibliographically approved
4. A Voyage to Africa by Mr Swift
Open this publication in new window or tab >>A Voyage to Africa by Mr Swift
2012 (English)In: Proceedings of the 15th International Conference on Information Fusion, IEEE conference proceedings, 2012, 808-815 p.Conference paper, Published paper (Refereed)
Abstract [en]

A male common swift Apus apus was equipped witha light logger on August 5, 2010, and again captured in his nest 298 days later. The data stored in the light logger enables analysis of the fascinating travel it made in this time period. The state of the art algorithm for geolocation based on light loggers consists in computing first sunrise and sunset from thelogged data, which are then converted to midday (gives longitude) and day length (gives latitude). This approach has singularities at the spring and fall equinoxes, and gives a bias for fast day transitions in the east-west direction. We derive a flexible particle filter solution, where sunset and sunrise are processed in separately measurement updates, and where the motion model has two modes, one for migration and one for stationary long time visits, which are designed to fit the flying pattern of the swift. This approach circumvents the aforementioned problems with singularity and bias, and provides realistic confidence bounds on the geolocation as well as an estimate of the migration mode.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2012
Keyword
Nonlinear filtering, Particle filter, Geolocation, Light levels
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-85905 (URN)978-0-9824438-4-2 (ISBN)978-1-4673-0417-7 (ISBN)
Conference
15th International Conference on Information Fusion (FUSION), Singapore, 9-12 July, 2012
Funder
Swedish Foundation for Strategic Research
Available from: 2012-12-03 Created: 2012-12-03 Last updated: 2013-07-10

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