Multiple Frequenzbänder für Lokalisation

Laufzeit: 01.01.2014 - 30.08.2016
Leitung: Prof. Dr.-Ing Horst Hellbrück
Mitarbeiter: Mathias Pelka

Hintergrund

Hohe Genauigkeit und Zuverlässigkeit bei der Lokalisation erreicht man mittels Funk-Laufzeitmessung (siehe GPS). Hierbei werden kurze Datenpakete im Mikrowellenbereich ausgesendet und die Zeit bis zum Eintreffen am Empfänger ermittelt. Über die bekannte Ausbreitungsgeschwindigkeit (Lichtgeschwindigkeit) wird die Entfernung berechnet. Um eine Auflösung von 30cm zu erreichen, ist eine Zeitsynchronisation mit einer Genauigkeit von 1ns notwendig. Die Anforderungen an die Zeitsynchronisation sind daher sehr hoch. 

Ziel

Ziel des Projekts ist es, ein System zur Ortung zu entwickeln, das Objekte in unterschiedlichen örtlichen Umgebungsbedingungen mit verschiedenen Genauigkeitsklassen orten kann. Je nach Größe und Beschaffenheit der Räumlichkeiten werden durch die flexible Wahl aus drei Frequenzbereichen 900 MHz, 2,4 GHz und 5,8 GHz, die gewünschte Genauigkeit und Reichweite erzielt. Die verwendete, handelsübliche Hardwareausstattung und die entwickelte Software bleiben dabei gleich: Die Funk-Chips inkl. Antennen können über Breakout-Boards ausgetauscht werden. Dadurch lässt sich der Zeitaufwand zur Installation und Inbetriebnahme des Systems minimieren, sowie die Herstellkosten durch Nutzung einer Plattformstrategie senken. 

Ansatz

Gegenstand dieses Forschungs- und Entwicklungsprojektes ist, drei ausgewählte Funk-Chips aus der Massenproduktion in drei unterschiedlichen Frequenzbereichen so zu ertüchtigen, dass das Senden und der Empfang ihrer Signale zur Funklaufzeitmessung genutzt werden kann. Aus Gründen der Standardisierung und Kostenreduktion ist das Ziel, mindestens zwei geeignete Chips zu finden und entsprechend aufzubereiten, die einer Chip-Familie angehören und wenn möglich Pin-kompatibel sind.

Arbeiten im Rahmen des m:flo Projektes

Es ergeben sich ständig neue Aufgaben im Rahmen des Forschungsprojektes. Sollten Sie eigene Ideen haben, die sich im Rahmen dieses Projektes verwirklichen wollen, schreiben Sie uns einfach an

Abgeschlossene Arbeiten:

Ergebnisse

Im m:flo Projekt wurden verschiedene Technologien auf ihre Eignung für das Lokalisationssystem untersucht. Dazu wurden kommerzielle Systeme, wie zum Beispiel CSS oder UWB Systeme, aber auch nicht kommerzielle Systeme, z.B. auf Basis von QR Codes, untersucht. 

Um Funklokalisationssysteme, wie z.B. auf UWB-basierte Systeme, auswerten zu können, ist hochspezialisiertes Messequipment notwendig. Hochgenaue Oszilloskope helfen Signalverläufe sichtbar zu machen. Es lassen sich damit Störungen, wie z.B. durch Mehrwegeausbreitung, untersuchen. Diese Ergebnisse helfen die Abstrahlcharakteristik der Antenne anzupassen, Leistungsmessungen durchzuführen oder um Störquellen zu identifizieren. 

UWB-Impuls in der Zeitdarstellung

 

Zur Auswertung wurden verschiedene Programme geschrieben. Diese sind zum Teil textbasiert und kondensieren sehr große Datenmengen auf relevante statistische Lageparameter, aber auch grafisch, wie im Bild gezeigt. 

3D-Visualisierung eines Indoor Positionierungssystems

3D-Visualisierung von UWB-Messdaten im Labor. 

Diese Visualiserung wurde mit UWB-Daten gewonnen. Das verwendete Positionierungssystem wurde von CoSA entwickelt und erreicht hohe Updateraten (über 200 Hz) bei hoher Tagdichte (über 50 Teilnehmer bei gleichbleibender Updaterate) und hohe Genauigkeit (mittlerer Positionierungsfehler von unter 30 cm). Die Visualisierung hilft z.B. bei der Annotation von Positionsdaten, um sofort Anomalien bei der Positionsberechnung festzustellen. Solche Anomalien treten z.B. durch Mehrwegeausbreitung auf. 

QR Transformer

Im Rahmen einer Abschlussarbeit, wurden graphische Codes, vornehmlich der QR Code, analysiert. Dabei wurde untersucht, wie durch Rücktransformationen die Grenzen der QR Erkennung erweitert werden können. Des weiteren sollte ermittelt werden, ob sich mittels QR Codes die Distanz und auch die Orientierung im Raum feststellen lassen. Die Abschlussarbeit wurde von Daniel Neckel erfolgreich zu Ende geführt.

Als Ergebnis enstand eine Android Anwendung, namens QRTransformer. Diese erlaubt es, QR Codes zu erstellen und durch manuelle oder automatische Rücktransformation wieder einzulesen. Die Anwendung ist in der Lage, die Distanz sowie den Winkel zwischen dem Smartphone und dem QR Code zu bestimmen.

 

Projektpartner

 

files/mflo/BMWi_Web_de_WBZ.gif

Förderkennzeichen: KF3177201ED3

files/mflo/zim_4c_klein.jpg

Technische Berichte

Um einen einfachen Demonstrator auf Basis von Distanzmessungen zu ermöglichen stellen wir hier in diesem Bericht ein einfaches Verfahren vor, um die Position zu bestimmen. 

Position Calculation with Least Squares based on Distance Measurements

 

Veröffentlichungen


Artikel and Buchkapitel
[2016] Survey of challenges and towards a unified architecture for location systems (Mathias Pelka, Horst Hellbrück), In Journal of Network and Computer Applications, volume 67, 2016. [bib] [pdf] [abstract]
Abstract Localization is a key aspect of emergent applications in the medical, industrial and consumer field. In this article we survey state of the art, identify current challenges and issues for localization systems and suggest a unified layered architecture. The analysis reveals that challenges cannot be addressed in an isolated manner for example, energy consumption is tied to the choice of algorithm and employed hardware. To separate various challenges and investigate them independently, we propose the concept of position providers. Position providers in the lower layers allow abstraction of positioning methods, positioning algorithms and positioning hardware. Thereby, a position provider encapsulates methods, algorithms and hardware. Furthermore, we suggest a classification of position providers inspired by related work. We propose a unified architecture for location systems which uses positioning and integration layers as main building blocks.
[2016] Iterative approach for anchor configuration of positioning systems (Mathias Pelka, Grigori Goronzy, Horst Hellbrück), In ICT Express, volume 2, 2016. [bib] [pdf] [abstract]
With anchor positions and measurements of distances between an object and anchors, positioning algorithms calculate the position of an object, e.g. via lateration. Positioning systems require calibration and configuration prior to operation. In the past, approaches employed reference nodes with GPS or other reference location systems to determine anchor positions. In this article, we propose an approach to determine anchor positions without prior knowledge. We evaluate our approach with simulations and real data based on the Decawave DW1000 radio and show that the error is proportional to the mean error of the distance estimation.
[2014] FULFILL - Framework zur Visualisierung, Speicherung und Filterung von Lokalisierungs-Messdaten (Lenka Hanesova, Horst Hellbrück), In ImpulsE, volume 18, 2014. [bib]
Konferenz Beiträge
[2016] S-TDoA - Sequential Time Difference of Arrival - A Scalable and Synchronization Free Approach for Positioning (Mathias Pelka, Horst Hellbrück), In IEEE Wireless Communications and Networking Conference, 2016. [bib] [abstract]
In the past various solutions for localization evolved to productive usage for wireless applications. These solutions are robust, precise and energy efficient. However, scalability, complexity and flexibility are still open issues. Especially, supported number of objects or update rates for localization are still limiting factors for the usage of the systems. In this work we suggest an approach called S-TDoA which stands for sequential Time Difference of Arrival that supports unlimited number of objects and high update rates. The key concept is a sequential triggering of anchors that send periodic messages. Tags determine their position by listening to the anchor messages and measuring time intervals. Additionally, this approach enhances security because tags are not visible as they do not send messages. We implement and evaluate S-TDoA in a localization system based on UWB-RF- Chips. The preliminary results demonstrate the advantages of our implementation regarding scalability and update rates as well as privacy.
[2016] Impact of Altitude Difference for Local Positioning Systems and Compensation with Two-Stage Filters (Mathias Pelka, Grigori Goronzy, Horst Hellbrück), In 2016 International Conference on Localization and GNSS, 2016. [bib] [abstract]
In range-based positioning systems, an altitude difference between tag and reference plane causes errors in two- and three-dimensional positioning. We analyze how these errors reduce accuracy of Local Positioning Systems (LPS) and show how compensation of the altitude difference improves performance of positioning. In this paper, we consider the availability of additional altitude information and transform the three-dimensional positioning problem into a two-dimensional problem. We provide algorithms for time-based positioning systems with a two-stage estimator for Two-Way Ranging and Time Difference of Arrival and incorporate additional altitude information. We simulate our approach for altitude difference compensation and provide an evaluation based on a Ultra-Wideband (UWB) radio with ranging capability and a barometric sensor for additional altitude information. A comparison is then made between our approach and standard solutions such as the Extended Kalman filter and the Unscented Kalman filter. Finally, the successful decrease in the positioning error for two- and three-dimensional positioning system, using the system disclosed herein, is illustrated. Based on our analysis, we derive practical solutions to deal with altitude differences for positioning systems.
[2016] Introduction, Discussion and Evaluation of Recursive Bayesian Filters for Linear and Nonlinear Filtering Problems in Indoor Localization (Mathias Pelka, Horst Hellbrück), In The Seventh International Conference on Indoor Positioning and Indoor Navigation, 2016. [bib] [abstract]
Linear and nonlinear filtering for state estimation (e.g. position estimation or sensor fusion) for indoor positioning and navigation applications is a challenging task. Sensor fusion becomes more important with cost-effective sensors being readily available. However, state estimation with recursive Bayesian filters for sensor fusion and filtering are difficult to apply. We present an overview for the general Bayesian filter and derive the most commonly used recursive Bayesian filters, namely the Kalman, extended Kalman and the unscented Kalman filter along with the particle filter. The later Kalman filters are extension of the original Kalman filter, which are able to solve nonlinear filtering problems. The particle filter is also able to solve nonlinear filtering problems. We evaluate the recursive Bayesian filters for linear and nonlinear filtering problems for sensor fusion from relative dead reckoning positioning data and absolute positioning data from an UWB positioning system. We discuss and evaluate performance and computational complexity and provide recommendations for the use case of the recursive Bayesian filters.
[2016] Investigation of Anomaly-based Passive Localization with Received Signal Strength for IEEE 802.15.4 (Marco Cimdins, Mathias Pelka, Horst Hellbrück), In The Seventh International Conference on Indoor Positioning and Indoor Navigation, 2016. [bib] [abstract]
Localization has important applications, for instance intrusion detection and elderly care. Such applications benefit from Device-free passive (DfP) localization systems, which employ received signal strength measurements (RSSM) to detect and track entities that neither participate actively in the localization process nor emit signals actively. RSSMs include received signal strength indicator (RSSI), energy detection (ED) and link quality indicator (LQI) measurements. This paper compares different packet-based RSSMs for DfP localization and presents detection results of a DfP anomaly-based detection system employed by IEEE 802.15.4 compliant devices. Furthermore, we investigate techniques for anomaly detection with continuous RSSI measurements.
[2015] Indoor Localization based on Bi-Phase Measurements for Wireless Sensor Networks (Mathias Pelka, Christian Bollmeyer, Horst Hellbrück), In 2015 IEEE Wireless Communications and Networking Conference (WCNC): - Track 3: Mobile and Wireless Networks (IEEE WCNC 2015 - Track 3- Mobile and Wireless Networks), 2015. [bib] [abstract]
Indoor localization is important for medical and industrial application as well as for wireless emergency and security systems. For such applications an accuracy within a few meters is desired. Available radio based systems within that accuracy are neither cost effective nor easy to deploy. In this work, we suggest an approach called biphase measurement based on phase measurements with two frequencies to determine the location of a tag. We design and build a complete indoor positioning system based on bi-phase measurements with easy to deploy wireless sensor nodes. The wireless sensor nodes shape anchors and tags and communicate results to a location engine of the indoor positioning system. Our implementation comprises lowcost IEEE802.15.4 radio chips with built-in support for phase measurements unit for both, anchor and tags. We compute the position of the tag based on distance estimation retrieved with bi-phase measurements. We evaluate our indoor positioning system providing first measurement results for accuracy and precision and discuss trade-off between scalability, real-time and accuracy.
[2015] Wireless Medical Sensors - Context, Robustness and Safety (Christian Bollmeyer, Mathias Pelka, Hartmut Gehring, Horst Hellbrück), In 49th annual conference of the German Society for Biomedical Engineering (BMT 2015) (Accepted), 2015. [bib]
[2014] Accurate Radio Distance Estimation by Phase Measurements with Multiple Frequencies (Mathias Pelka, Christian Bollmeyer, Horst Hellbrück), In The Fifth International Conference on Indoor Positioning and Indoor Navigation 2014 (IPIN 2014), 2014. [bib] [abstract]
Indoor localization is beneficial for logistics, industrial applications and for several consumer applications. In the area of logistics, e.g. warehouses, localization accuracy within a few meters is desired. Available radio based systems within that accuracy are neither cost effective nor easy to deploy. Distance estimations are one possible method for localization. In this work, we propose phase measurements between two wireless sensor nodes for distance estimation. We introduce a mathematical model to estimate distances from phase measurements with multiple frequencies and provide a systematic analysis of possible sources of errors. Additionally, we derive requirements, e.g. resolution and speed for a phase measurement unit to reach certain accuracy. To proof our theoretical results, we present evaluation results based on our implementation. Our implementation comprises a low cost IEEE 802.15.4 hardware with a built-in phase measurement unit. We implement the developed algorithm for distance estimation in our wireless sensor network and use two wireless sensor nodes to perform a phase measurement. The contribution of the paper comprises a new model for phase measurements to estimate distances and a preliminary evaluation with our hardware.
[2014] Evaluation of Radio Based, Optical and Barometric Localization for Indoor Altitude Estimation in Medical Applications (Christian Bollmeyer, Mathias Pelka, Hartmut Gehring, Horst Hellbrück), In The Fifth International Conference on Indoor Positioning and Indoor Navigation, 2014. [bib] [abstract]
The advances of electronics provide options for improved monitoring of patients in clinical environment.Medical applications like blood pressure monitoring require precise and wireless altitude measurement in indoor environment. An error of only a few centimeters may lead to mistreatment of patients.Furthermore, user requirements like small form factor, usability and robust operation are important in the medical field.Existing evaluations of indoor localization systems focus on accuracy analysis of x- and y-coordinates and not on the z-coordinate (altitude). In this paper, we define evaluation criteria for altitude estimation in medical applications. We compare an Ultra-Wide-Band indoor localization system, an optical Microsoft Kinect camera system and our own development of a wireless barometric sensor against these criteria. We present a comparative measurement setup, results and a final evaluation of the three systems in an indoor environment.
Workshop Beiträge
[2016] Comparison of wired and wireless synchronization with clock drift compensation suited for U-TDoA localization (Swen Leugner, Mathias Pelka, Horst Hellbrück), In 13th Workshop on Positioning, Navigation and Communication, 2016. [bib] [abstract]
Indoor localization with Uplink Time Difference of Arrival (U-TDoA) provides good scalability, high updates rates and high accuracy. However, clock errors lead to localization errors and synchronization is important. In this paper, we design and implement wired and wireless synchronization and provide a comparison between them. We design and implement a wireless synchronization with clock drift compensation. For wired and wireless synchronization, we discuss reasons for clock deviation that lead to localization errors. We evaluate both approaches in a U-TDoA measurement setup. Finally, we provide recommendations for wired and wireless synchronization.
[2015] Mobile Robot Seamless Localization with Localization Optimized QR Codes (Mathias Pelka, Daniel Neckel, Horst Hellbrück), In 12th Workshop on Positioning, Navigation and Communication, 2015. [bib] [abstract]
Indoor navigation is a prerequisite for new emerging applications for autonomous mobile robots. Additionally to the location of a robot, the orientation is important for these applications. Furthermore, a solution to this localization problem should be inexpensive and easy extensible for new areas of a building. We propose inexpensive optical landmarks based on localization optimized Quick Response (QR) code for localization of the landmark within an image to reduce computational cost. We further specify the error correction level, border, and size of the QR code for optimal localization. The proposed QR code combines GPS coordinates and local coordinates which allows seamless integration of our approach. We perform image processing to estimate the distance and orientation of a mobile robot with respect to the localization optimized QR code. To evaluate our approach we implemented the approach in an Android application and measured the performance in experiments. Additionally, we suggest a method to retrieve more accurate GPS information based on the measured orientation and distances. Our implementation achieves update rates of up to 3 Hz and an accuracy of 1 cm
Sonstige Veröffentlichungen
[2016] Investigation of Anomaly-based Passive Localization with IEEE 802.15.4 (Marco Cimdins, Mathias Pelka, Horst Hellbrück), Technical report, RWTH Aachen University, 2016. [bib] [pdf]
[2015] Position Calculation with Least Squares based on Distance Measurements (Mathias Pelka), Technical report, Fachhochschule Lübeck, 2015. [bib]
[2015] Comparison and Performance Evaluation of Indoor Localization Algorithms based on an Error Model for an Optical System (Z. Lifang, M. Pelka, C. Bollmeyer, H. Hellbrück), GRIN (T. M. Buzug et. al., ed.), 2015. [bib]
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