<p>Unmanned aerial vehicles (UAVs) equipped with imaging systems and integrated global navigation satellite system/inertial navigation system (GNSS/INS) are used for a variety of applications. Disaster relief, infrastructure monitoring, precision agriculture, and ecological forestry growth monitoring are among some of the applications that utilize UAV imaging systems. For most applications, accurate 3D spatial information from the UAV imaging system is required. Deriving reliable 3D coordinates is conditioned on accurate geometric calibration. Geometric calibration entails both spatial and temporal calibration. Spatial calibration consists of obtaining accurate internal characteristics of the imaging sensor as well as estimating the mounting parameters between the imaging and the GNSS/INS units. Temporal calibration ensures that there is little to no time delay between the image timestamps and corresponding GNSS/INS position and orientation timestamps. Manual and automated spatial calibration have been successfully accomplished on a variety of platforms and sensors including UAVs equipped with frame and push-broom line cameras. However, manual and automated temporal calibration has not been demonstrated on both frame and line camera systems without the use of ground control points (GCPs). This research focuses on manual and automated spatial and temporal system calibration for UAVs equipped with GNSS/INS frame and line camera systems. For frame cameras, the research introduces two approaches (direct and indirect) to correct for time delay between GNSS/INS recorded event markers and actual time of image exposures. To ensure the best estimates of system parameters without the use of ground control points, an optimal flight configuration for system calibration while estimating time delay is rigorously derived. For line camera systems, this research presents the direct approach to estimate system calibration parameters including time delay during the bundle block adjustment. The optimal flight configuration is also rigorously derived for line camera systems and the bias impact analysis is concluded. This shows that the indirect approach is not a feasible solution for push-broom line cameras onboard UAVs due to the limited ability of line cameras to decouple system parameters and is confirmed with experimental results. Lastly, this research demonstrates that for frame and line camera systems, the direct approach can be fully-automated by incorporating structure from motion (SfM) based tie point features. Methods for feature detection and matching for frame and line camera systems are presented. This research also presents the necessary changes in the bundle adjustment with self-calibration to successfully incorporate a large amount of automatically-derived tie points. For frame cameras, the results show that the direct and indirect approach is capable of estimating and correcting this time delay. When a time delay exists and the direct or indirect approach is applied, horizontal accuracy of 1–3 times the ground sampling distance (GSD) can be achieved without the use of any ground control points (GCPs). For line camera systems, the direct results show that when a time delay exists and spatial and temporal calibration is performed, vertical and horizontal accuracy are approximately that of the ground sample distance (GSD) of the sensor. Furthermore, when a large artificial time delay is introduced for line camera systems, the direct approach still achieves accuracy less than the GSD of the system and performs 2.5-8 times better in the horizontal components and up to 18 times better in the vertical component than when temporal calibration is not performed. Lastly, the results show that automated tie points can be successfully extracted for frame and line camera systems and that those tie point features can be incorporated into a fully-automated bundle adjustment with self-calibration including time delay estimation. The results show that this fully-automated calibration accurately estimates system parameters and demonstrates absolute accuracy similar to that of manually-measured tie/checkpoints without the use of GCPs.</p>

Wireless personal area networks have emerged as an important communication infrastructure in areas such as at-home healthcare and home automation, independent living and assistive technology, as well as sports and wellness. Wireless personal area networks, including body sensor networks, are becoming more mature and are considered to be a realistic alternative as communication infrastructure for demanding services. However, to transmit data from e.g., an ECG in wireless networks is also a challenge, especially if multiple sensors compete for access. Contention-based networks offer simplicity and utilization advantages, but the drawback is lack of predictable performance. Recipients of data sent in wireless sensor networks need to know whether they can trust the information or not. Performance measurements, monitoring and control is of crucial importance for medical and healthcare applications in wireless sensor networks. This thesis focuses on development, prototype implementation and evaluation of a performance management system with performance and admission control for wireless sensor networks. Furthermore, an implementation of a new method to compensate for clock drift between multiple wireless sensor nodes is also shown. Errors in time synchronization between nodes in Bluetooth networks, resulting in inadequate data fusion, are also analysed. / <p>QC 20120529</p>

Body sensor networking is a rapidly growing technology. Today wearable sensors are used to measure and monitor e.g. pulse, temperature, skin conductance, heart activity, and movement (through GPS or inertial measurement units). Mobile phones can act as coordinating nodes in wireless personal area networks used in home automation, healthcare, sport and wellness e.g. to measure pulse and distance. Integration of data from multiple sources sensors (data fusion) means that data from each sensor node needs to be associated with data from other sensor nodes sampled at approximately the same time. Accurate methods for time synchronization are therefore a necessary prerequisite for reliable data fusion. This thesis studies time synchronization problems in Bluetooth piconets between multiple wireless sensor nodes connected to a mobile phone that acts as coordinating node. Three different algorithms to enable correct data fusion have been developed, implemented and evaluated. The first is a single clock solution that synchronizes multiple wireless sensor nodes based solely on the mobile phone’s clock. The other two algorithms synchronize the clocks in sensor nodes to the clock in the coordinating node. / <p>QC 20130605</p>

La synchronisation temporelle est la première opération effectuée par le démodulateur. Elle permet d'assurer que les échantillons transmis aux processus de démodulation puissent réaliser un taux d'erreurs binaires le plus faible.Dans cette thèse, nous proposons l'étude d'algorithmes innovants de synchronisation temporelle à haute performance.D'abord, nous avons proposé des algorithmes exploitant l'information souple du décodeur en plus du signal reçu afin d'améliorer l'estimation aveugle d'un retard temporel supposé constant sur la durée d'observation.Ensuite, nous avons proposé un algorithme original basé sur la synchronisation par lissage à faible complexité.Cette étape a consisté à proposer une technique opérant dans un contexte hors ligne, permettant l'estimation d'un retard aléatoire variable dans le temps via les boucles d'aller-retour sur plusieurs itération. Les performances d'un tel estimateur dépassent celles des algorithmes traditionnels.Afin d'évaluer la pertinence de tous les estimateurs proposés, pour des retards déterministe et aléatoire, nous avons évalué et comparé leurs performances à des bornes de Cramèr-Rao que nous avons développées pour ce cadre. Enfin, nous avons évalué les algorithmes proposés sur des signaux WBAN. / Time synchronization is the first function performed by the demodulator. It ensures that the samples transmitted to the demodulation processes allow to achieve the lowest bit error rate.In this thesis we propose the study of innovative algorithms for high performance time synchronization.First, we propose algorithms exploiting the soft information from the decoder in addition to the received signal to improve the blind estimation of the time delay. Next, we develop an original algorithm based on low complexity smoothing synchronization techniques. This step consisted in proposing a technique operating in an off-line context, making it possible to estimate a random delay that varies over time on several iterations via Forward- Backward loops. The performance of such estimators exceeds that of traditional algorithms. In order to evaluate the relevance of all the proposed estimators, for deterministic and random delays, we evaluated and compared their performance to Cramer-Rao bounds that we developed within these frameworks. We, finally, evaluated the proposed algorithms on WBAN signals.

Global Navigation Satellite System/Inertial Measurement Unit (GNSS/IMU) Integrated Navigation Systems (INS) integrate the positive features of GNSS and IMU for optimal navigation guidance in high accuracy outdoor navigation systems, for example using Extended Kalman Filter (EKF) techniques. Time synchronization of IMU data with precise GNSS based time is necessary to accurately synchronize the two systems. This must be done in real-time for time sensitive navigation applications such as autonomous vehicles. The research is done in two parts. The first part is the simulation of inaccurate time-stamping in a single axis of nonlinear input data in a gyroscope and an accelerometer, to obtain the timing error value that is tolerable by a high accuracy GNSS/INS system. The second part is the creation of a real-time algorithm using an STM32 embedded system enabled with FreeRTOS real-time kernel for a GNSS receiver and antenna, along with an IMU sensor. A comparative analysis of the time synchronized system and an unsynchronized system is done based on the errors produced using gyroscope and accelerometer readings along a single axis from the IMU sensor, by conducting static and rotational tests on a revolving chair.The simulation concludes that a high accuracy GNSS/INS system can tolerate a timing error of up to 1 millisecond. The real-time solution provides IMU data paired with updated GNSS based time-stamps every 5 milliseconds. The timing jitter is reduced to a range of ±1 millisecond. Analysis of final angular rotation error and final position error from gyroscope and accelerometer readings respectively, indicate that the real-time algorithm produces a reduction in errors when the system is static, but there is no statistical evidence showing the reduction of errors from the results of the rotational tests. / GNSS / IMU integrerade navigationssystem kombinerar de positiva egenskaperna hos GNSS och IMU för optimal prestanda i noggranna navigationssystem. Detta görs med hjälp av sensorfusion, till exempel EKF. Tidssynkronisering av IMU-data med exakt GNSS-baserad tid är nödvändigt för att noggrant synkronisera de två systemen. Detta måste göras i realtid för tidskänsliga navigationsapplikationer såsom autonoma fordon. Forskningen görs i två delar. Den första delen är simulering av icke-linjär rörelse i en axel med felaktig tidsstämpling hos ett gyroskop och en accelerometer. Detta görs för att erhålla det högsta tidsfel som är acceptabelt hos ett GNSS / INS-system med hög noggrannhet. Den andra delen är skapandet av en realtidsalgoritm med ett inbyggt STM32-system med FreeRTOS som realtidskärna för en GNSSmottagare och antenn, tillsammans med en IMU-sensor. En jämförande analys av det tidssynkroniserade systemet mot ett osynkroniserat system görs baserat på de positionsfel längs en axel som produceras av gyroskopoch accelerometermätningar. Detta görs genom att utföra statiska och roterande tester med hjälp av en roterande stol.Simuleringen visar att ett noggrant GNSS / INS-system tolererar ett tidsfel på upp till 1 millisekund. Realtidslösningen ger IMU-data med tidsstämplar synkroniserade med GNSS-tid var femte millisekund. Tidsjittret reduceras till ett intervall mellan ± 1 millisekund. Analysen av det slutliga vinkelrotationsfelet och positionsfelet från gyroskopoch accelerometermätningar indikerar att realtidsalgoritmen ger ett lägre fel när systemet är statiskt. Det finns dock inga statistiska bevis för förbättringen från resultaten av rotationstesterna.

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The Frequency Disturbance Recorder (FDR) is a specialized data acquisition device designed to monitor fluctuations in the overall power system. The device is designed such that it can be attached by way of a standard wall power outlet to the power system. These devices then transmit their calculated frequency data through the public internet to a centralized data management and storage server. By distributing a number of these identical systems throughout the three major North American power systems, Virginia Tech has created a Frequency Monitoring Network (FNET). The FNET is composed of these distributed FDRs as well as an Information Management Server (IMS). Since frequency information can be used in many areas of power system analysis, operation and control, there are a great number of end uses for the information provided by the FNET system. The data provides researchers and other users with the information to make frequency analyses and comparisons for the overall power system. Prior to the end of 2004, the FNET system was made a reality, and a number of FDRs were placed strategically throughout the United States. The purpose of this thesis is to present the elements of a new generation of FDR hardware design. These elements will enable the design to be more flexible and to lower reliance on some vendor specific components. Additionally, these enhancements will offload most of the computational processing required of the system to a commodity PC rather than an embedded system solution that is costly in both development time and financial cost. These goals will be accomplished by using a Field Programmable Gate Array (FPGA), a commodity off-the-shelf personal computer, and a new overall system design. / Master of Science

Η ΒΥΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της. / Τα ψηφιακά συστήματα UWB (Ultra Wide-Band) παρέχουν τη δυνατότητα ασύρματης μετάδοσης σε πολύ υψηλό ρυθμό. Λόγω του μεγάλου εύρους ζώνης, το κανάλι εισάγει πολλαπλές ανακλάσεις οι οποίες φέρουν μεγάλο ποσοστό της ωφέλιμης ενέργειας του μεταδιδόμενου σήματος. Η ικανότητα του δέκτη για σύλληψη όσο το δυνατόν περισσότερης ωφέλιμης ενέργειας έχει αντίκτυπο στη συνολική απόδοση του συστήματος. Η χρήση της τεχνικής διαμόρφωσης με πολύπλεξη συχνότητας ορθογωνίων φερουσών (OFDM), που στην συγκεκριμένη περίπτωση (UWB) συνδυάζεται με πολυζωνική (Multi-band) μετάδοση, απλοποιεί τη διαχείριση του συνολικού φάσματος συχνοτήτων. Όμως η διαμόρφωση OFDM παρουσιάζει ιδιαίτερη ευαισθησία σε προβλήματα τόσο διασυμβολικής παρεμβολής (ISI) όσο και διακαναλικής παρεμβολής (ICI), λόγω του έντονου διασκορπιστικού χαρακτήρα του καναλιού καθώς επίσης και τυχόν αποκλίσεων που εμφανίζονται στους ταλαντωτές πομπού-δέκτη. Τα παραπάνω επιβάλλουν τη χρήση σύνθετων αλγορίθμων συγχρονισμού και συντονισμού (time and frequency synchronization) μεταξύ πομπού και δέκτη για την ομαλή λειτουργία. Στα πλαίσια της διπλωματικής αυτής θα πραγματοποιηθεί επιλογή κατάλληλων αλγορίθμων για τα προαναφερθέντα προβλήματα, οι οποίοι θα πρέπει να πληρούν τις προδιαγραφές του υπό διαμόρφωση διεθνούς προτύπου 802.15.3α και θα αναπτυχθούν βέλτιστες αρχιτεκτονικές VLSI, με στόχο τόσο το χαμηλό κόστος υλοποίησης όσο και την χαμηλή κατανάλωση ισχύος. / In this project have been studied the low power VLSI architecture for synchronization algorithms in Multi-band UWB Wireless systems. The main issues are timing and frequency synchronization algorithms.

Tillämpning av instrument vid utövande av explosiva idrottsgrenar, för att mäta en atlets kraftproduktion, kan användas vid analys för att fastställa hur bra en atlet presterar. Dessa typer av instrument finns på marknaden och är oftast tillämpade för sprintstarter och har funktionen att man kanfånga en atlet på film och koppla en händelse till det data som hämtats in via instrumentet. Nackdelenmed dessa system är att de antingen är väldigt dyra eller är i avsaknaden av att vara smidiga ochportabla då de oftast levereras med mycket kringutrustning.Syftet med detta examensarbete var att utveckla ett system bestående av en mobilapplikation, samtlogik till en mikrokontroll som registrerar den horisontella kraften vid sprintstarter från en analogkälla. Insamlade data beräknas och skickas sedan med hjälp av BLE-kommunikation till mobilapplikationen som presenterar kraftdata för användaren.Utöver detta var syftet även att få inhämtad kraftdata tidssynkroniserad mot en mobil enhet för attgöra det möjligt att utvärdera händelser mot externa källor som IMU och höghastighetsfilm.Resultatet av arbetet visar att det är möjligt att hämta samplade kraftdata från en mikrokontroll viaBLE-kommunikation. Det går även att presentera beräknade kraftdata visuellt för en slutanvändaremed en mobilapplikation och få händelserna tidssynkroniserade med hjälp av tidssynkroniseringsalgoritmer. Resultaten kan emellertid förbättras genom fortsatt utveckling av detta system. / The application of instruments in the practice of explosive sports, to measure an athlete's force production, can be used to determine how well an athlete performs. Present instruments on the marketare most often applied to sprint starts and function to capture an athlete on film, and link the eventto the data retrieved from the instrument. The disadvantages with present day systems are that theyare either too expensive or lack flexibility and portability as they are usually delivered with a lot ofperipherals.The purpose of this thesis was to develop a system of a mobile application and logical code to a microcontroller that register horizontal forces at sprint starts from an analog source. The collected datawas calculated and transmitted using BLE communication to the mobile application which presentsthe force data to the user.Moreover, the purpose was also to have the acquired force data time-synchronized with a mobile device to make it possible to evaluate events against external sources such as IMU and high-speed film.The result for the logic developed throughout this work demonstrate that it is possible to retrievesampled force data from a microcontroller via BLE communication. It was possible to present thecalculated force data visually to an end user with a mobile application and have the events time synchronized using time synchronization algorithms. However, the results can be further improved bydevelopment of the system.

Studien syftar till att analysera mätningar av tidsfördröjningar i inbyggda system som använder externa Wi-Fi-moduler och Network Time Protocol (NTP) för tidssynkronisering. Mätning i detta sammanhang innebär att man tar mätbara data som kan representera tidsfördröjningarna i numerisk form, vilket gör det möjligt att analysera och jämföra dem på ett objektivt sätt. Genom en grundlig litteraturstudie identifierades de olika elementen involverade i tidssynkroniseringsprocessen, inklusive egenskaper hos Wi-Fi-moduler, NTP-protokollet och andra systemkomponenter. Insamlad data analyserades för att upptäcka mönster och tendenser i tidsfördröjning. Det övergripande målet med studien var att bidra med specifika insikter som kan förbättra konfigurationen och prestandan hos inbyggda system. Genom att jämföra prestanda hos olika dataenheter och visa på variationer i tidsfördröjning, har studien gett konkreta mätdata i form av tid, dess genomsnitt och standardavvikelse. Dessa insikter kan användas för att designa mer tillförlitliga inbyggda system med förbättrad tidssynkronisering, vilket är avgörande för mcu som kräver hög precision och stabilitet. / The study aims to analyze the measurements of time delays in embedded systems that use external Wi-Fi modules and the Network Time Protocol (NTP) for time synchronization. Measurement in this context means taking measurable data that can represent time delays in numerical form, making it possible to analyze and compare them objectively. Through a thorough literature review, the various elements involved in the time synchronization process were identified, including the characteristics of Wi-Fi modules, the NTP protocol, and other system components. Collected data were analyzed to detect patterns and trends in time delays. The overall goal of the study was to contribute specific insights that can improve the configuration and performance of embedded systems. By comparing the performance of different data units and showing variations in time delays, the study provided concrete guidelines and recommendations for engineers and developers. These insights can be used to design more reliable embedded systems with improved time synchronization, which is crucial for mcu requiring high precision and stability.