Dissertations / Theses on the topic 'Sonar tracking'

The domain below the surface in maritime security is hard to monitor with conventional methods, due to the often very noisy environment. In conventional methods the measurements are thresholded in order to distinguish potential targets. This is not always a feasible way of treating measurements. In this thesis a system based on raw measurements, that are not thresholded, is presented in order to track and classify divers with an active sonar. With this system it is possible to detect and track weak targets, even with a signal to noise ratio that often goes below 0 dB.

The system in this thesis can be divided into three parts: the processing of measurements, the association of measurements to targets and the classification of targets. The processing of measurements is based on a particle filter using Track Before Detect (TBD). Two algorithms for association of measurements, Joint Probabilistic Data Association (JPDA) and Highest Probability Data Association (HPDA), have been implemented. The classification of targets is done using an assumed novel approach. The system is evaluated by doing simulations with approximately 8 hours of recorded data, where divers are present at nine different times. The simulations are done a number of times to catch The classification rate is high and the false alarm rate is low.

Undervattensdomänen är svår att övervaka i marina säkerhetssystem med sedvanliga metoder, på grund av den brusiga miljön. I traditionella metoder trösklas mätningarna för att urskilja potentiella mål. Detta är inte alltid ett godtagbart sätt att behandla mätningar på. I den här rapporten presenteras ett system baserat på behandling av rå mätdata, som inte trösklas, för att spåra och klassificera dykare med en aktiv sonar. Med detta system är det möjligt att detektera och spåra svaga mål, trots att signal till brus förhållandet ofta går under 0 dB.

Systemet i den här rapporten kan delas upp i tre delar: behandling av mätningar, association av mätningar till mål samt klassificering av mål. Behandlingen av mätningarna görs med ett partikelfilter som använder Track Before Detect (TBD). Två algoritmer för associering av mätningar, Joint Probabilistic Data Association (JPDA) och Highest Probability Data Association (HPDA), har implementerats. Klassificeringen av mål görs med en egenutvecklad metod som inte har hittats i existerande dokumentation. Systemet utvärderas genom att simuleringar görs på ungefär 8 timmar inspelad data, där dykare är närvarande vid nio olika tillfällen. Simuleringarna görs ett antal gånger för att fånga upp stokastiska beteenden. Andelen lyckade klassificeringar är hög och andelen falsklarm är låg.

Target tracking is one the most fundamental elements of a radar system. The aim of target tracking is the reliable estimation of a target'
s true state based on a time history of noisy sensor observations. In real life, the sensor data may include substantial noise. This noise can render the raw sensor data unsuitable to be used directly. Instead, we must filter the noise, preferably in an optimal manner. For land, air and surface marine vehicles, very successful filtering methods are developed. However, because of the significant differences in the underwater propagation environment and the associated differences in the corresponding sensors, the successful use of similar principles and techniques in an underwater scenario is still an active topic of research. A comparative study of the effects of the underwater environment on a number of tracking algorithms is the focus of the present thesis. The tracking algorithms inspected are: the Kalman Filter, the Extended Kalman Filter and the Particle Filter. We also investigate in particular the IMM extension to KF and EKF filters. These algorithms are tested under several underwater environment scenarios.

This thesis investigates the detection and classification of small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to parameters in the boats engine and propeller. A novel signal processing method for detection and discrimination of noise radiated from small boats has been developed. There are two main components to the algorithm. The first component detects the presence of small boats by the harmonic tonals radiated from the boat propeller and engine. The second component was designed to extract the a signature from passive sonar data. The Harmonic Extraction and Analysis Tool (HEAT) was designed to estimate the fundamental frequency of the harmonic tones, track the fundamental frequency using a Kalman filter, and automatically extract the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. The algorithm is shown to accurately extract theses signatures, and results show that the signatures are unique enough that the same boat passing by the hydrophone multiple times can be recognized.

Object tracking is important in autonomous robotics, military applications, financial time-series forecasting, and mobile systems. In order to correctly track through clutter, algorithms which predict the next value in a time series are essential. The competence of standard machine learning techniques to create bearing prediction estimates was examined. The results show that the classification based algorithms produce more accurate estimates than the state-of-the-art statistical models. Artificial Neural Networks (ANNs) and K-Nearest Neighbour were used, demonstrating that this technique is not specific to a single classifier.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 357-364).
In this thesis, a fully autonomous and persistent bistatic anti-submarine warfare (ASW) surveillance solution is developed using the autonomous underwater vehicles (AUVs). The passive receivers are carried by these AUVs, and are physically separated from the cooperative active sources. These sources are assumed to be transmitting both the frequency-modulated (FM) and continuous wave (CW) sonar pulse signals. The thesis then focuses on providing novel methods for the AUVs/receivers to enhance the bistatic sonar tracking performance. Firstly, the surveillance procedure, called the Automated Perception, is developed to automatically abstract the sensed acoustical data from the passive receiver to the track report that represents the situation awareness. The procedure is executed sequentially by two algorithms: (i) the Sonar Signal Processing algorithm - built with a new dual-waveform fusion of the FM and CW signals to achieve reliable stream of contacts for improved tracking; and (ii) the Target Tracking algorithm - implemented by exploiting information and environmental adaptations to optimize tracking performance. Next, a vehicular control strategy, called the Perception-Driven Control, is devised to move the AUV in reaction to the track report provided by the Automated Perception. The thesis develops a new non-myopic and adaptive control for the vehicle. This is achieved by exploiting the predictive information and environmental rewards to optimize the future tracking performance. The formulation eventually leads to a new information-theoretic and environmental-based control. The main challenge of the surveillance solution then rests upon formulating a model that allows tracking performance to be enhanced via adaptive processing in the Automated Perception, and adaptive mobility by the Perception-Driven Control. A Unified Model is formulated in this thesis that amalgamates two models: (i) the Information-Theoretic Model - developed to define the manner at which the FM and CW acoustical, the navigational, and the environmental measurement uncertainties are propagated to the bistatic measurement uncertainties in the contacts; and (ii) the Environmental-Acoustic Model - built to predict the signal-to-noise power ratios (SNRs) of the FM and CW contacts. Explicit relationships are derived in this thesis using information theory to amalgamate these two models. Finally, an Integrated System is developed onboard each AUV that brings together all the above technologies to enhance the bistatic sonar tracking performance. The system is formulated as a closed-loop control system. This formulation provides a new Integrated Perception, Modeling, and Control Paradigm for an autonomous bistatic ASW surveillance solution using AUVs. The system is validated using the simulated data, and the real data collected from the Generic Littoral Interoperable Network Technology (GLINT) 2009 and 2010 experiments. The experiments were conducted jointly with the NATO Undersea Research Centre (NURC).
by Raymond Hon Kit Lum.
Sc.D.

The use of multi-sensor systems entails a Data Fusion and Sensor Management requirement in order to optimize the use of resources and allow the synergistic operation of sensors. To date, data fusion and sensor management have largely been dealt with separately and primarily for centralized and hierarchical systems. Although work has recently been done in distributed and decentralized data fusion, very little of it has addressed sensor management. In decentralized systems, a consistent and coherent approach is essential and the ad hoc methods used in other systems become unsatisfactory. This thesis concerns the development of a unified approach to data fusion and sensor management in multi-sensor systems in general and decentralized systems in particular, within a single consistent information-theoretic framework. Our approach is based on considering information and its gain as the main goal of multi-sensor systems. We develop a probabilistic information update paradigm from which we derive directly architectures and algorithms for decentralized data fusion and, most importantly, address sensor management. Presented with several alternatives, the question of how to make decisions leading to the best sensing configuration or actions, defines the management problem. We discuss the issues in decentralized decision making and present a normative method for decentralized sensor management based on information as expected utility. We discuss several ways of realizing the solution culminating in an iterative method akin to bargaining for a general decentralized system. Underlying this is the need for a good sensor model detailing a sensor's physical operation and the phenomenological nature of measurements vis-a-vis the probabilistic information the sensor provides. Also, implicit in a sensor management problem is the existence of several sensing alternatives such as those provided by agile or multi-mode sensors. With our application in mind, we detail such a sensor model for a novel Tracking Sonar with precisely these capabilities making it ideal for managed data fusion. As an application, we consider vehicle navigation, specifically localization and map-building. Implementation is on the OxNav vehicle (JTR) which we are currently developing. The results show, firstly, how with managed data fusion, localization is greatly speeded up compared to previous published work and secondly, how synergistic operation such as sensor-feature assignments, hand-off and cueing can be realised decentrally. This implementation provides new ways of addressing vehicle navigation, while the theoretical results are applicable to a variety of multi-sensing problems.

Detection and tracking of signals used in sonar applications in noisy environment is the focus of this thesis. We have concentrated on the low Signal-to-Noise Ratio (SNR) case where the conventional detection methods are not applicable. Furthermore, it is assumed that the duty cycle is relatively low. In the problem that is of concern the carrier frequency, pulse repetition interval (PRI) and the existence of the signal are not known. The unknown character of PRI makes the problem challenging since it means that the signal exists at some unknown intervals. A recursive, Bayesian track-before-detect (TBD) filter using particle filter based methods is proposed to solve the concerned problem. The data used by the particle filter is the magnitude of a complex spectrum in complex Gaussian noise. The existence variable is added in the design of the filter to determine the existence of the signal. The evolution of the signal state is modeled by a linear stochastic process. The filter estimates the signal state including the carrier frequency and PRI. Simulations are done under different scenarios where the carrier frequency, PRI and the existence of the signal varies. The results demonstrate that the algorithm presented in this thesis can detect signals which cannot be detected by conventional methods. Besides detection, the tracking performance of the filter is satisfying.

Detection of an underwater target with active sonar in shallow waters such as the Baltic sea is a big challenge. This since the sound beams from the sonar will be reflected on the surfaces, sea surface and sea bottom, and the water volume itself which generates reverberation. Reverberation which will be reflected back to the receiver, is strong in intensity which give rise to many false targets in terms of classifying a target in a surveillance area. These false targets are unwanted and a real target might benefit from these miss-classifications in terms of remaining undetected. It is especially hard if the signal-to-noise ratio (SNR) is approaching zero, i.e. the target strength and the reverberation strength are equal in magnitude. The classical approach to a target detection problem is to assign a threshold value to the measurement, and the data point exceeding the threshold is classified as a target. This approach does not hold for low levels of SNR, since a threshold would not have a statistical significance and could lead to neglecting important data. Track-before-detect (TrBD) is a proposed method for low-SNR situations which tracks and detects a target based on unthresholded data. TrBD enables tracking and detecting of weak and/or stealthy targets. Due to the issues with target detection in shallow waters, the hypothesis of this thesis is to investigate the possibility to implement TrBD, and evaluate the performance of it, when applied on a low-SNR target. The TrBD is implemented with a particle filter which is a recursive Bayesian solution to the problem of integrated tracking and detection. The reverberation data was generated by filtering white noise with an Autoregressive filter of order 1. The target is assigned to propagate according to a constant velocity state space model. Two types of TrBD algorithms are implemented, one which is trained on the background and one which is not. The untrained TrBD is able to track and detect the target but only for levels of SNR down to 4dB. Lower SNR leads to the algorithm not being able to distinguish the target signal from the reverberation. The trained TrBD on the other hand, is able to perform very well for levels of SNR down to 0dB, it is able to track and detect the target and neglect the reverberation. For trajectories passing through areas with high reverberation, the target was lost for a short period of time until it could be retracked again. Overall, the TrBD was successfully implemented on the self-generated data and has a good performance for various target trajectories.

Approved for public release; distribution is unlimited.
For an Autonomous Underwater Vehicle to complete many operational missions, it must have the ability to maintain its position relative to the ocean floor. Maintaining station requires that the AUV be able to determine the direction and the distance displaced during a small time interval. Knowing the direction and distance traveled in a measured amount of time, the magnitude and direction of the ocean current can be calculated. Once this ocean current information is known, the AUV speed and direction can be properly adjusted to directly offset the ocean current forces. This thesis will attempt to determine, by computer simulation, if the first problem of AUV station keeping, vehicle movement direction and distance detection can be performed using bottom-tracking sonar as the AUV's only sensor. Both the problems of performing and storing successive synthetic sonar images and of determining AUV motion using frame to frame correlation of these images are investigated. (RRH)

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This research investigates the use of two versions of a batch-oriented, multidimensional assignment tracking algorithm to examine target crossings that are on the order of 100 scans in duration. The simulations use outputs in one dimension (bearings only) from a passive sonar line array. Linear programming relaxation is used to solve the assignment problem for an exhaustive set of measurement-to-track N-tuple costs along the batch. The implementation of the cost evaluations used for the objective function is analyzed for efficiency. The objective function is minimized subject to certain constraints. The constraints are set up such that each measurement-to-track assignment is exclusive per scan along the batch. The algorithm is generic and can be extended to N dimensions (ND). Missing measurements are accounted for as part of the assignment model. An efficient version of the ND assignment is developed to increase the batch length for acceptable runtime performance. Batch lengths of up to 15 scans, equivalent to a 16D assignment, have been developed and tested on various levels of clutter data. Results are tested via 100-trial Monte Carlo simulations for the two algorithms as applied to the long-duration passive sonar crossing targets case with various clutter density and filter settings.

A steady signal exerts two complementary effects on a noisy acoustic environment: one is to add energy, the other is to create order. The ear has evolved mechanisms to detect both effects and encodes the fine temporal detail of a stimulus in sequences of auditory nerve discharges. Taking inspiration from these ideas, this thesis investigates the use of regular timing for sonar signal detection. Algorithms that operate on the temporal structure of a received signal are developed for the detection of merchant vessels. These ideas are explored by reappraising three areas traditionally associated with power-based detection. First of all, a time-frequency display based on timing instead of power is developed. Rather than inquiring of the display, "How much energy has been measured at this frequency? ", one would ask, "How structured is the signal at this frequency? Is this consistent with a target? " The auditory-motivated zero crossings with peak amplitudes (ZCPA) algorithm forms the starting-point for this study. Next, matters related to quantitative system performance analysis are addressed, such as how often a system will fail to detect a signal in particular conditions, or how much energy is required to guarantee a certain probability of detection. A suite of optimal temporal receivers is designed and is subsequently evaluated using the same kinds of synthetic signal used to assess power-based systems: Gaussian processes and sinusoids. The final area of work considers how discrete components on a sonar signal display, such as tonals and transients, can be identified and organised according to auditory scene analysis principles. Two algorithms are presented and evaluated using synthetic signals: one is designed to track a tonal through transient events, and the other attempts to identify groups of comodulated tonals against a noise background. A demonstration of each algorithm is provided for recorded sonar signals.

The purpose of this project was to investigate how efficient it is to implement steering of a solar panel, in one or two axes. To determine how efficient it is, special consideration was taken to the energy usage of the driving system. Practical applications have also been considered with pros and cons. To answer the research questions a prototype was built and a controlled environment for testing was arranged. Rotating the panel in one axis resulted in a 26% energy increase and for the two-axis system a 56% energy increase compared to stationary panel. The use of stepper motors turned out to be not as efficient as needed, due to continuous use of energy at all times during operation.
Syftet med detta projekt var att undersöka hur effektivt det är att implementera styrning av en solpanel i en eller två axlar. För att kunna avgöra nyttan så togs det hänsyn till drivsystemet och hur mycket energi det gick åt för styrningen. Även praktiska tillämpningar kontrollerades och vilka fördelar och nackdelar som skulle erhållas. För att svara på frågeställningarna, tillverkades en prototyp som testades i en kontrollerad miljö. Genom att rotera panelen runt en axel ökar energiupptaget 26 % och för det tvåaxliga systemet 56 % jämfört med en stationär panel. Användningen av stegmotorer visade sig inte vara speciellt effektiv då det krävdes kontinuerlig strömmatning för att erhålla det motormoment som krävdes för att hålla panelen på plats.

Syftet med detta projekt är att undersöka om det ärmöjligt att erhålla mer energi från en solpanel om solpanelenalltid är riktad mot solen. Vidare ska två frågor angåendeom det är möjligt att konstruera ett system som effektivtföljer solen med ljussensorer och hur komplicerad dentillhörande mjukvaran blir besvaras. För att finna svar pådessa frågor har en prototyp skapats.Detta projekt består av tre avgörande delar, hårdvara,mjukvara och elektronik. Stegmotorer används för att roterasolpanelerna och light dependent resistor (LDR)-motståndanvänds som ljussensorer.Med det solspårande systemet erhölls 48 % mer energifrån solpanelerna.
The purpose of this project is to investigate if it is possibleto get more energy out of a solar panel if the solarpanel is always directed towards the sun. Furthermore,two questions surrounding the plausibility of building anefficient tracking system, and the level of complexity forthe required software and mechanism will be investigated.To be able to answer these questions a prototype was built.This project consists of three major parts, hardware,software and electronics. Stepper motors were used to rotatethe solar panels and light dependent resistors (LDR)were used as light sensors.With the tracking system, the solar panels outputted48 % more energy.

The purpose of this project is to investigate if it is possible to get more energy out of a solar panel if the solar panel is always directed towards the sun. Furthermore, two questions surrounding the plausibility of building an efficient tracking system, and the level of complexity for the required software and mechanism will be investigated. To be able to answer these questions a prototype was built. This project consists of three major parts, hardware, software and electronics. Stepper motors were used to rotate the solar panels and light dependent resistors (LDR) were used as light sensors. With the tracking system, the solar panels outputted 48 % more energy.
Syftet med detta projekt är att undersöka om det är möjligt att erhålla mer energi från en solpanel om solpanelen alltid är riktad mot solen. Vidare ska två frågor angående om det är möjligt att konstruera ett system som effektivt följer solen med ljussensorer och hur komplicerad den tillhörande mjukvaran blir besvaras. För att finna svar på dessa frågor har en prototyp skapats. Detta projekt består av tre avgörande delar, hårdvara, mjukvara och elektronik. Stegmotorer används för att rotera solpanelerna och light dependent resistor (LDR)-motstånd används som ljussensorer. Med det solspårande systemet erhölls 48 % mer energi från solpanelerna.

Approved for public release; distribution is unlimited
Wind loads on sun tracking solar reflector panels exposed to the atmospheric boundary layer were established through surface static pressure measurements to determine how wind affects them, specifically at the request of SPAWAR-Pacific, which has developed a custom design. A 1:8 scale model of a four-panel array was studied in the Naval Postgraduate School wind tunnel. Wind velocity, wind angle orientation, and individual panel positions, at which the highest pressure coefficient cases were anticipated, were varied. The pressure coefficients were measured by an array of Scanivalve pressure transducers with 16 pressure taps drilled into the top and bottom surfaces of each panel. Oil flow and smoke flow visualization techniques were performed to better understand the flow features that led to the greatest pressure coefficients. A parapet was included to observe the wind effects of various positions. Additionally, pressure measurements were observed using a rounded edge installed on the lead panel edges. This notion was to assist in not only minimizing wind loads, but also in determining a safe stow position of the array during high wind events. The measurements and the flow visualization studies both provided a cohesive and constructive picture of the flow. The windward panel was found to be subjected to the thrust of the wind loads in most cases, with a maximum recorded differential pressure coefficient of 3.25. However, when in combination with attaching the rounded edge to the windward panel and setting it negative five degrees, pressure coefficients were decreased by more than 70%. Parapets of the appropriate help also reduced the measured loads significantly.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 91-92).
This thesis discusses the design, implementation, and testing of a buck converter with peak power tracking. The peak power tracker uses a perturb and observe algorithm to actively track the solar panel's peak power point and a global sweep algorithm accounts for startup and multiple local maxima. The tracker takes the place of the current mode loop in the converter's control scheme by providing a battery with peak charging current. A voltage mode loop is also designed to take over control from the tracker to complete the multi-loop structure. A solar panel simulator is designed to mimic the characteristics of an actual solar panel to allow careful testing of the tracking algorithms. A test circuit board is built and its operation is verified. Finally, the power extracting potential of the active tracking method from this thesis is compared to two simpler solar regulators.
by Jeremy Michael Cohen.
M.Eng.

Reference is increasingly being made towards the need for the world to find new and renewable forms of energy, especially for electric power generation, but also for space heating and the heating of water. Solar energy is one of the cheapest forms of renewable energy available and is so far one of the most underutilised resources. One contribution makes reference to the way forward as being ‘using concentrating solar power which uses parabolic mirrors to focus the solar heat (energy) and generate steam to drive electric generators’ as is currently happening in the utility power marketplace in the USA. This thesis deals with the issues surrounding the original development of a two axis solar energy tracking system (SET) in 1997. The subsequent redesign, development and upgrade, undertaken from 2002 to 2006, with its performance and efficiency being measured in 2006 and 2007 using a specially configured measurement and recording system. A Solar Energy Tracker (SET) is designed to track the sun moving in two axes, reflecting the solar radiation received on its mirrors to a target mounted at the end of a boom, at the focal point of the mirrors. In late 2005 and early 2006, a solar thermal hot water manufacturer and installer heard about the developments and requested some form of involvement, especially if Christchurch Polytechnic Institute of Technology (CPIT) provided research input and assisted in the further development and testing of solar thermal hot water systems. This sponsor offered two projects in 2006 and again in 2007. Other solar thermal hot water suppliers also requested involvement in the research and development being performed at CPIT, which led in August 2006, December 2006, June 2007 and December 2007, to a number of other solar thermal hot water and air wall systems being installed. Progressively, the roof of C block at CPIT has become full of solar thermal hot water systems and solar air wall systems, both of the conventional type and those with newer technologies at the core of their development. This thesis outlines the stages in the redesign and development of the SET, and the various stages in its testing, development and refinement up to its present form. The thesis chapters are written based around the mechanical and electrical design, the auto-tracking and daylight controls, the PLC (programmable logic controller) controller, the mirror and substrate testing, the SCADA (Supervisory Control And Data Acquisition) system, the testing and comparison with other domestic solar thermal hot water systems and finally the testing of the SET itself. It also details the future developments and outlines possible uses for the SET in its redefined form. With clean and polished mirrors the SET has proven itself capable of achieving a temperature rise across the target of 15 °C at a flow rate of 4 l/m. On some occasions this temperature rise can be in excess of 20 °C, but testing thus far, has shown this cannot be sustained for any worthwhile period of time (15-30 minutes). This translates to an efficiency of 5-10 % when related to an energy produced per twenty four hour time period. However, if the efficiency is calculated for the actual period of generation, ‘generation efficiency,’ then this figure rises to 24 %. An overview is given of associated solar thermal hot water and solar air wall system research and development (that is ongoing at CPIT) as well as the performance and efficiency graphs for the solar thermal hot water systems on test. No manufacturer’s, industry or brand trade names are mentioned, as this research is still confidential and commercially sensitive. However, the technology involved and characterised by each solar thermal system is recorded in a generic sense. The SET was originally developed with the purpose of heating hot water and today this is still the intent. The possible applications for this hot water are many and varied from electricity generation, space heating and further into developing or new industrial processes. The performances of the other domestic solar thermal hot water systems currently under test, are compared with the figures from the SET, with the maximum efficiency, presently available, being from an evacuated tube heat pipe system at up to 65 %, whereas traditional finned flat plate technologies have efficiencies after twelve months of up to 48 %.

This thesis presents a method of tracking and correcting for the swaying of a central receiver tower in concentrated solar production plants. The method uses a camera with image processing algorithms to detect movement of the center of the tower. A prototype was constructed utilizing a CMOS camera connected to a microcontroller to control the movements of three surrounding heliostats. The prototype uses blob-tracking algorithms to detect and correct for movements of a colored model target. The model was able to detect movements in the tower with average error of 0.32 degrees, and was able to correctly orient the surrounding heliostats to within 1.2 and 2.6 degrees of accuracy while testing indoors and outdoors, respectively.

Photovoltaic (solar electric) technology has shown significant potential as a source of practical and sustainable energy; this study focuses on increasing the performance of photovoltaic systems through the use of improved control and power interfaces. The main objective is to find an effective control algorithm and topology that are optimally suited to extracting the maximum power possible from photovoltaic modules. The thesis consists of the following primary subjects: photovoltaic modelling, the topological study of photovoltaic interfaces, the regulation of photovoltaic voltage, and maximum power tracking. In photovoltaic power systems both photovoltaic modules and switching mode converters present non-linear and time-variant characteristics, resulting in a difficult control problem. This study applies in-depth modelling and analysis to quantify these inherent characteristics,s pecifically using successive linearization to create a simplified linear problem. Additionally, Youla Parameterisation is employed to design a stable control system for regulating the photovoltaic voltage. Finally, the thesis focuses on two critical aspects to improve the performance of maximum power point tracking. One improvement is to accurately locate the position of the maximum power point by using centred differentiation. The second is to reduce the oscillation around the steady-state maximum power point by controlling active perturbations. Adopting the method of steepest descent for maximum power point tracking, which delivers faster dynamic response and a smoother steady-state than the hill climbing method, enables these improvements. Comprehensive experimental evaluations have successfully illustrated the effectiveness of the proposed algorithms. Experimental evaluations show that the proposed control algorithm harvests about 1% more energy than the traditional method under the same evaluation platform and weather conditions without increasing the complexity of the hardware.

The solar concentration performance of a tracking, flat-base, line-focusing Fresnel mirror was investigated in this study. The Fresnel mirror consists of flat mirror strips situated on a base and oriented at appropriate angles to focus incident light to a desired line. Simple optical ray tracing and energy conservation were used to develop a mathematical model of the concentrator assuming small or zero diurnal tracking errors. The model analyzed the concentrator design and provided detailed expressions for the geometric evaluation of the concentrated sunlight rays in the focal plane above the mirror. The local concentration ratio and the geometric concentration ratio were introduced to describe the intensity profile in the focal plane and the average concentration of sunlight on a target absorber. Included in the model were losses of incident sunlight due to imperfect reflection, nonreflecting portions of the base, and blockage by adjacent mirror strips when imperfect tracking occurs.Based on the analytical model and using the Ada high level language, a computer program was written to simulate the concentrator. To facilitate performance comparisons, a baseline concentrator design was adopted. To study the effects of imperfect tracking, performance data were generated for small tracking errors up to approximately two and one-half degrees. The effects of design variations were studied by varying the concentrator focal length, strip width, and base width.Simulation results demonstrated that the concentration characteristics were highly sensitive to tracking error. Intensity profile shifts relative to the target caused the highest losses in intercepted sunlight.Design decisions were found to dramatically affect the concentration character- istics. For the baseline concentrator under perfect tracking conditions, an optimum focal length was identified. Except for the disadvantage of added costs, decreased strip widths was found to be a way to increase both the maximum and average concentration ratio for the absorber. Using smaller strip widths might, however, critically affect the energy intercepted by the target under imperfect tracking. Increasing the concentrator base width increased the total amount of power in the focal plane, with a higher maximum concentration ratio and additional tailing of the intensity profile.
Department of Physics and Astronomy

En 2011, la capacité totale installée du Photovoltaïque au Canada était de 289 MW et elle pourrait atteindre entre 9 et 15 GW d'ici 2025. Selon des études antérieures, des systèmes de suivi solaires PV peuvent capturer 20% à 50% plus de rayonnement solaire que les systèmes fixes. Un suiveur solaire est un dispositif qui maintient les panneaux photovoltaïques perpendiculaires aux rayons du soleil. Il y a un manque de connaissances sur la performance des systèmes solaires photovoltaïques de suivi d'exploitation dans les conditions météorologiques sévères du Canada. Trois objectifs principaux ont été définis pour cette recherche. Le premier objectif est l'évaluation des performances en fonction de la stratégie de suivi pour les systèmes PV. Cet objectif est atteint par la simulation et l'analyse de quatre systèmes PV: horizontal fixe, incliné fixe, suivi selon un axe et suivi selon deux axes. Ces systèmes sont analysés au cours des périodes annuelles, mensuelles et journalières. Quatre villes avec des conditions météorologiques différentes ont été étudiées: Montréal (Canada), Casablanca (Maroc), Ouagadougou (Burkina Faso), et Olympia (USA). Les résultats obtenus à partir de simulations montrent que les systèmes de suivi selon deux axes présentent les rendements les plus élevés dans tous les endroits choisis. Le deuxième objectif est de déterminer l'orientation optimale d'un système d'exploitation PV dans des conditions climatiques du Canada. Cet objectif est atteint en enquêtant sur la météo et les conditions environnementales du Canada qui touchent les systèmes PV, y compris les basses températures en hiver et le rayonnement réfléchi par la neige (effet albédo). Le rayonnement réfléchi par la neige cumulée sur le sol entraîne une augmentation de l'irradiation des panneaux jusqu'à 4,1%, 5,6% et 6,9% pour les systèmes inclinées, avec suivi selon un axe, et avec suivi selon deux axes pendant l'hiver, respectivement. Les systèmes de suivis selon un axe et deux axes reçoivent 28% et 33% de plus de rayonnement solaire que le système incliné sur un an. De plus, le suivi du soleil pourrait précipiter le phénomène de fusion de la glace et de la neige accumulée sur les panneaux photovoltaïques. L'objectif final de cette thèse est le choix de la méthode de suivi optimale pour le Canada. Cet objectif est atteint par l'analyse de diverses orientations des systèmes PV dans les jours typiques: une journée d'hiver claire, une claire journée d'été, et une journée nuageuse d’hiver et d’été. Selon les analyses quotidiennes, le suivi du soleil est efficace les jours de soleil direct (clairs), contre-productif les jours nuageux, et dépend de l'indice de clarté dans les jours très nuageux. Ces résultats sont corroborés par des recherches antérieures. Les résultats permettent de proposer une méthode qui permet de suivre le soleil dans des conditions claires et d’aller à la position horizontale dans des conditions nuageuses. En conditions nuageuses partielles, la stratégie de suivi à adopter dépend de l'indice de clarté et de rayonnement réfléchi par le sol.

The SIUe solar car team lacks a competitive communication system. To enable the competitive edge a major upgrade to the electronics and wiring was required. A new maximum power point tracker and driver support system was developed to give them the competitive edge.

2010 - 2011
Our planet faces significant challenges in the twenty-first century because energy consumption is expected to double globally during the first half of this century. Faced with increasingly constrained oil supplies, humanity must look to other sources of energy, such as solar, to help us meet the growing energy demand. A useful measure of the level of a country’s development is through its energy consumption and efficiency. Excessive fossil fuel energy use not only has caused severe and growing damage to the environment from greenhouse gas emissions and oil spills, but also has brought political crises to countries in the form of global resource conflicts and food shortages. Solar and other forms of renewable energy offer a practical, clean, and viable solution to meet our planet’s growing environmental and energy challenges. Solar radiation is the most important natural energy resource because it is a renewable, free and largely diffused source. The Sun provides the Earth with an enormous amount of energy. Naturally, the Sun has always held the attention of humanity and been the subject of worship by many cultures over the millennia, such as the Egyptians, Incans, Greeks, and Mayans, among many others. The potential of solar energy to produce heat and electricity to be supplied for our modern economies in a variety of productive activities has been widely demonstrated but not yet widely adopted around the globe due to relatively cheap fossil fuels. The main problem of this kind of energy source is that it is not constant during the day and not readily dispatched. In contrast, modern lifestyles demand a continuous and reliable supply of energy. However, there are ways to overcome these shortfalls. In chapter 1 there is a general presentation of solar irradiance and the main solar angles: global solar irradiance is composed by diffuse, reflected and direct radiation. To direct radiation the geometrical relationship between the Sun and the Earth must be known. Nowadays solar technologies are involved to industrial maturity: to capture solar energy as much as possible firstly arrays with an optimal fixed tilt have been developed, then solar tracking arrays. For many of reasons, especially energetic, environmental, economic, a big interest nowadays has been developed for hybrid vehicles, particularly hybrid electric vehicles HEV; but in recent years HSV are attracting increasing interest. The last ones use solar energy. These kind of vehicles are described in chapter 2. It must be underlined that there is a great difference between hybrid solar vehicles and solar cars: in fact solar cars now do not represent a realistic alternative for traditional cars, because they depend only on sun availability and have high costs. Instead HSV do not have problems concerning the autonomy range, because they have an electric motor and also a traditional combustion engine. However until now in literature a little interest has been given to the hybrid solar vehicles despite HEV but at the University of Salerno a prototype of HSV has been developed and another one is going to be developed. Formulating the control algorithm for determining the fuel efficient power split between two energy sources is referred to as the supervisory control or energy management problem. In chapter 3, the main control strategies, used also for the energy management of HEV, are examined. Control strategies may be classified into non-causal and causal controllers respectively. Furthermore, a second classification can be made among heuristic, optimal and sub-optimal controllers. Great importance has given to three different strategies: Dynamic Programming DP, Genetic Algorithm GA and Rule–Based strategy RB. For each one the techniques of optimizations are described. An HSV vehicle has been modeled, and for this model especially RB strategy and GA optimization have been applied to see the most convenient one to apply on HSV prototype developed at University of Salerno. So a comparison of RB strategy with the other two is shown, and its advantages and facilities are described through experimental data. In chapter 3 this comparison shows that the adoption the results obtained by the optimization through RB strategy are close to the ones obtained with the other two optimizations. So this strategy seems convenient for two main reasons: · the previous knowledge of the driving cycle is not always required; · there are not strict mathematical operations. For these reasons RB strategy has been applied: it has been shown that it is necessary to compute the mean value of power traction and to establish the value of the sun factor. P tr can be evaluated with a backward or forward strategy: · Backward: the mean value is evaluated on the previous knowledge of the data, taking the mean value of the power during a certain period; · Forward: the mean value of the power is predicted. In chapter 4 numeric and experimental results about the application of this optimization strategy have been shown. First of all fuel consumption has been computed through a program developed in MATLAB, taking driving cycle from literature: it has been demonstrated that the values of fuel consumptions computed with backward and forward strategies of power traction are not very different. Then, through experimental tests, the adoption of on-board solar energy prediction is presented and there is also the demonstration of the beneficial to select the best solution in terms of energy management. Finally the program, previously developed for a generic HSV, has been adapted to the HSV prototype developed at University of Salerno considering also experimental driving cycles: the validation of Rule–Based strategy applied on the HSV prototype is presented through experimental tests. After it has been decided to adopt RB strategy for the on- board energy management of the HSV prototype through the adaptation of the MATLAB program into a program developed in LabVIEW. In chapter 5 a moving solar roof for an Hybrid Solar Vehicle is presented, and differences between a tracking system for mobile and fixed applications are underlined. With an optimal orientation of the roof, that means when the angle of incidence between the normal to the roof and the sun ray tends to zero, there is a considerable gain of energy. The mobile solar roof has been realized as a parallel robot with three degrees of freedom. A mathematical model has been developed in MATLAB, the design has been realized through the software 3D SolidWorks, the control system had been realized at the beginning with a PLC, then with a webcam placed in the middle of the mobile roof and the control has been developed through a program realized in LabVIEW. The model of the proposed roof has been developed and validated over experimental data obtained by a small scale real prototype. The kinematic model presented has allowed the optimization of roof geometry and shape. The best orienting properties are reached with shapes approaching a circular one, and with the minimum distance between globular joints. The optimal solution has been determined by an integrated analysis of both roof and vehicle shape. The economic feasibility of this project but especially the energetic gain has been evaluated: this model has been designed to be mobile only during parking phases for two main reasons: · The HSV analyzed must be used only for a urban use, so the driving phase lasts only 1-2 hours and the largest part of the day is a parking phase; · If the solar roof is mobile also during the driving phase some aerodynamic losses and instabilities could happen. The adoption of a moving solar roof for vehicle applications can substantially enhance the energy recovered during parking phases, for a solar electric or hybrid vehicle. Moreover, this system can result particularly useful at high latitudes, where an horizontal panel would be strongly penalized by low sun height. The adoption of a moving roof can therefore extend the potential market of solar assisted vehicles. In order to maximize benefits of the mobile solar roof, the energy consumption related to its movement must be minimized, and unnecessary movements avoided. To this end, a control procedure based on the use of insulation data provided by the solar panel, information derived by a GPS module and by processing the sky images taken by a webcam has been presented. The webcam has been placed in the middle of the mobile platform of the prototype, it makes a picture of the sky; in this picture two points are signed: the center of the picture and the center of mass of the points with maximum brightness. The main idea is that the center of the picture tends to go on the center of mass of the points of maximum brightness. Through this control system it has been also valuated the best interval between two different orientations, and the result is that during the day the interval between two different orientation changes, and it is convenient to orient the roof in the middle of each intervals, that means that if it has been computed that the best interval at 9.00 a.m. is one hour, there is a bigger gain of solar energy if the roof is oriented at 9.00 a.m. with the best orientation of 9.30 a.m. until 10a.m. and so on. [edited by author]
X n.s.

In order to understand the migration patterns of migrating birds, it is necessary to understand whenand where to they migrate. Many of these birds are very small and thus cannot carry heavy sensors;hence it is necessary to be able to perform positioning using a very small sensor. One way to do this isto use a light-intensity sensor. Since the sunrise and sunset times are known given time and position onthe earth, it is possible to determine the global position using light intensity. Light intensity increasesas the sun rises. Data sets from several calibration sensors, mainly from different locations in Sweden, have been examinedin different ways in order to get an understanding of the measurements and what affects them. Inorder to perform positioning, it is necessary to know the solar elevation angle, which can be computedif the time and position are known, as is the case for the calibration sensors. This has been utilized toidentify a mapping from measured light intensity to solar elevation angle, which is used to computepseudo-measurements for target tracking, described below. In this thesis, positioning is performed using methods from the field of target tracking. This is doneboth causally (filtering) and non-causally (smoothing). There are certain problems that arise; firstly,the measured light intensity can be attenuated due to weather conditions such as cloudiness, which ismodelled as a time-varying offset. Secondly, the sensor can be shadowed causing outliers in the data.Furthermore, birds are not always in a migratory state, they oftentimes stay in one place. The lattertwo phenomena are modelled using an Interacting Multiple Model (IMM) where they are representedas discrete states, corresponding to different models.

Based on a study of existing solar filament and tracking methods, a fully automated solar filament detection and tracking method is presented. An adaptive thresholding technique is used in a segmentation phase to identify candidate filament pixels. This phase is followed by retrieving the actual filament area from a region grown filament by using statistical parameters and morphological operations. This detection technique gives the opportunity to develop an accurate spine extraction algorithm. Features including separation distance, orientation and average intensities are extracted and fed to a Neural Network (NN) classifier to merge broken filament components. Finally, the results for two consecutive images are compared to detect filament disappearance events, taking advantage of the maps resulting from converting solar images to Heliographic Carrington co-ordinates. The study has demonstrated the novelty of the algorithms developed in terms of them now all being fully automated; significantly the algorithms do not require any empirical values to be used whatsoever unlike previous techniques. This combination of features gives the opportunity for these methods to work in real-time. Comparisons with other researchers shows that the present algorithms represent the filaments more accurately and evaluate computationally faster - which could lead to a more precise tracking practice in real-time. An additional development phase developed in this dissertation in the process of detecting solar filaments is the detection of filament disappearances. Some filaments and prominences end their life with eruptions. When this occurs, they disappear from the surface of the Sun within a few hours. Such events are known as disappearing filaments and it is thought that they are associated with coronal mass ejections (CMEs). Filament disappearances are generally monitored by observing and analysing successive solar H-alpha images. After filament regions are obtained from individual H-alpha images, a NN classifier is used to categorize the detected filaments as Disappeared Filaments (DFs) or Miss-Detected Filaments (MDFs). Features such as Area, Length, Mean, Standard Deviation, Skewness and Kurtosis are extracted and fed to this neural network which achieves a confidence level of at least 80%. Comparing the results with other researchers shows high divergence between the results. The NN method shows better convergence with the results of the National Geophysical Data Centre (NGDC) than the results of the others researchers.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
Amid the great crisis of the energy, new methods for electric power generation, especially those do not harm the environment, are constantly sought to meet the growing need worldwide. Among them, the use of Fresnel linear concentrators becomes increasingly feasible, due to have lower cost in comparison to other types of solar concentrators. Thus, the project seeks to develop techniques that optimize use of the system where the main objective is to implement and validate the tracking system for a prototype of linear Fresnel solar concentrator, operating between approximately 7:30 and 16:30 in Fortaleza, CearÃ. For that, it used microcontrollers, sensors and motors to design a system capable of tracking Solar light system. The characterization and validation of the inductive position sensor used is also an important part of the work. To perform the tracking system, have been used a theoretical methodology for relative location of the sun, beyond the gain scheduling technique in control of employee movement. The position sensor validation have a maximum error than 0.3Â. Therefore, can consider that, with the use of the techniques employed for the achievement of system of control, the medium error obtained was about 0.06Â, making the design perform the concentration of solar rays in the absorber concentrator with a maximum deviation of 0.5Â, providing the desired reliability for system use.
Em meio Ãs grandes crises no ambiente energÃtico novos mÃtodos para geraÃÃo de energia elÃtrica, principalmente aqueles que nÃo agridem o meio ambiente, sÃo procurados constantemente para suprir a crescente necessidade mundial. Dentre eles, o uso de concentradores Solares do tipo Fresnel linear torna-se cada vez mais viÃvel, devido possuir custo inferior a outros tipos de concentradores solar. Com isso, procura-se desenvolver tÃcnicas que otimizem o uso do modelo onde o principal objetivo deste trabalho à implementar e validar o sistema de rastreamento de um protÃtipo de concentrador solar Fresnel linear, com funcionamento compreendido aproximadamente entre 7:30 e 16:30 h, na cidade de Fortaleza, CearÃ. Para tanto, utilizou-se microcontroladores, sensores e motores para projetar um sistema capaz de rastrear a luz Solar. A caracterizaÃÃo e validaÃÃo do sensor de posiÃÃo indutivo utilizado tambÃm à parte importante do trabalho. Para a realizaÃÃo do rastreamento empregou-se uma metodologia teÃrica para localizaÃÃo relativa do Sol, alÃm da tÃcnica de escalonamento de ganho no controle do movimento empregado. A validaÃÃo do sensor de posiÃÃo foi realizada encontrando-se um erro mÃximo em torno de 0,3Â. Portanto, pode-se considerar que, com a utilizaÃÃo das tÃcnicas abordadas para a realizaÃÃo do controle do sistema o erro mÃdio obtido foi cerca de 0,06Â, fazendo com que o projeto realizasse a concentraÃÃo dos raios solares no absorvedor do concentrador com um desvio mÃximo de 0.5Â, fornecendo ao sistema a confiabilidade desejada para sua utilizaÃÃo.

The detection and tracking of underwater targets with active sonar is a challenging problem because of high acoustic clutter, fluctuating target returns and a relatively low measurement update rate. In this thesis, a Bayesian framework for the detection and tracking of underwater targets using active sonar is formulated. In general, Bayesian tracking algorithms are built on two statistical models: the target dynamics model and the measurement model. The target dynamics model describes the evolution of the target state with time and is almost always assumed to be a Markov process. The typical measurement model approximates the sensor image with a collection of discrete points at each frame and allows point measurement tracking to be performed. This thesis investigates alternative target and measurement models and considers their application to active sonar tracking. The Markov process commonly used for target modelling assumes that the state evolves without knowledge of its future destination. Random realisations of a Markov process can also display a large amount of variability and do not, in general, resemble realistic target trajectories. An alternative is the reciprocal process, which assumes conditioning on a known destination state. The first key contribution is the derivation and implementation of a Maximum Likelihood Sequence Estimator (MLSE) for a Hidden Reciprocal Process (HRP). The performance of the proposed algorithm is demonstrated in simulated scenarios and shown to give improved state estimation performance over Markov processes for scenarios featuring reciprocal targets. In point measurement tracking, reducing the sensor data to point detections results in the loss of valuable information. This method is generally sufficient for tracking high Signal-to-Noise Ratio (SNR) targets but can fail in the case of low SNR targets. The alternative to point measurement tracking is to provide the sensor intensity map, an image, as an input into the tracker. This paradigm is referred to as Track-Before-Detect (TkBD). This thesis will focus on a particular TkBD algorithm based on Expectation-Maximisation (EM) data association called the Histogram-Probabilistic Multi-Hypothesis Tracker (H-PMHT) as it handles multiple targets with low complexity. In the second key contribution, we demonstrate a Viterbi implementation of the H-PMHT algorithm, and show that it outperforms the Kalman Filter in the linear non-Gaussian case. A problem with H-PMHT is that it fails to model fluctuating target amplitude, which can degrade performance in realistic sensing conditions. The third key contribution addresses this by replacing the multinomial measurement model with a Poisson mixture process. The new Poisson mixture is shown to be consistent with the original H-PMHT modelling assumptions but it now allows for a randomly evolving mean target amplitude state with instantaneous fluctuations. This new TkBD algorithm is referred to as the Poisson H-PMHT. The Bayesian prior on the target state is also modified to ensure more robust performance. The fourth contribution is a novel TkBD algorithm based on the application of EM data association to a new measurement model that directly describes continuous valued intensity maps and avoids using an intermediate quantisation stage like the H-PMHT. This model is referred to as the Interpolated Poisson measurement model and is integrated into the Probabilistic Multi-Hypothesis Tracker (PMHT) framework to derive a TkBD algorithm for continuous data called the Interpolated Poisson-PMHT (IP-PMHT). The performance of the Poisson H-PMHT and IP-PMHT algorithms are verified through simulations and are shown to outperform the standard H-PMHT in terms of SNR estimation, particularly for scenarios featuring targets with highly fluctuating amplitude. The final key contribution is the application of several TkBD algorithms based on EM data association to the active sonar problem through a comparative study using trial data from an active towed array sonar. The TkBD algorithms are modified to incorporate changes in target appearance with received array bearing, and are shown to give improved SNR and state estimation performance compared with a conventional point measurement tracking algorithm. The thesis concludes by discussing the limitations of the proposed algorithms and possible avenues for future work.
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2015

The exploration of oceans and sea beds is being made increasingly possible through the development of Autonomous Underwater Vehicles (AUVs). This is an activity that concerns the marine community and it must confront the existence of notable challenges. These include, for example, mining minerals, inspecting pipeline and mapping oceans, sampling in contaminated water. Also, there has been another growing interest for security forces in precluding submarines or intruders from a beach or harbour entrance as well as hunting shallow water mines. However, an automatic detecting and tracking system is the first and foremost element for an AUV or an aqueous surveillance network. Since accurate surrounding information is essential in order to manoeuvre the AUV efficiently and economically, while corrupt information can jeopardize an entire mission. By extracting the space information form sensors, an AUV can achieve the localisation and mapping which are currently two primary concerns in the robotics research. Meanwhile, such information will provide a fundament of protection for surface vessels or troops, harbour infrastructure and oil plant against the enemy and terrorism. Acoustic sensors are commonly used to detect and position underwater obstacles, suspicious objects or to map the surroundings because sound waves can propagate more appreciable distances than electromagnetic and optical energy in the water. The measurements from these sensors, however, are always bound up with noises and errors. Various underwater activities may further pollute sound signals and then threaten the AUV navigation process. To simplify the detection procedure, some researchers make use of acoustic beacons or apparent obstructions (such as rocks, concrete walls) because they have distinctive characteristics. Point or line features are extracted from the acoustic signals or images for localization and mapping purposes. The long propagation range of sound waves can present new problems when acoustic sensors operate in confined environments, such as water tanks, rivers and harbours. The multiple reflections will be recorded by the sensor and result in false alarms. Furthermore, with advances in manufacturing techniques, the downsizing in marine explosive ordnances is progressing significantly, making it more difficult to discriminate between surface reflections and explosive ordnances. Finally, under the consideration of cost effectiveness, a mechanically scanned sonar has been introduced for the AUV in this research. However, the sensor beam cannot cover a large region simultaneously and a moving object may be distorted in the acoustic image because of the relatively low scanning speed. Due to such distortions in the data flows, objects may be indistinguishable from random noise or reverberation in acoustic images. The research presented here addresses the afore-mentioned problems relating to the theme of automatic detection from acoustic images. It is concerned with the detection and tracking of small underwater objects in order to protect autonomous underwater vehicles using sonar (SOund Navigation and Range). In the present study, these vehicles operated in laboratory water tanks or natural river environments. This research made use of self provided analytical studies that differentiated between reverberation and real object echoes. Detections were achieved automatically by using signal and image processing techniques. This research consists of three important and linked strategies. Firstly, a simple and fast reverberation suppression filter was provided, based on the understanding of the mechanism of the sonar sensor. Secondly, a robust detection system was developed to perceive small suspended obstacles in the water. Thirdly and finally, arc features were successfully extracted from the acoustic images and mathematical maps were generated from those features. The majority of experiments were derived from the elliptical water tank and the River Torrens, Adelaide, South Australia. For this project, a sequence of sonar images was taken from the same sonar location in the elliptical water tank. Further, a sequence of sonar images was taken from a sequence of sonar locations in the natural river. They provided different data sets for the assessment and evaluation of self developed algorithms. Results shown in this thesis confirm the favourable outcomes of the investigation and applied methodology.
Thesis (M.Eng.Sc.) -- University of Adelaide, School of Mechanical Engineering, 2010

The exploration of oceans and sea beds is being made increasingly possible through the development of Autonomous Underwater Vehicles (AUVs). This is an activity that concerns the marine community and it must confront the existence of notable challenges. These include, for example, mining minerals, inspecting pipeline and mapping oceans, sampling in contaminated water. Also, there has been another growing interest for security forces in precluding submarines or intruders from a beach or harbour entrance as well as hunting shallow water mines. However, an automatic detecting and tracking system is the first and foremost element for an AUV or an aqueous surveillance network. Since accurate surrounding information is essential in order to manoeuvre the AUV efficiently and economically, while corrupt information can jeopardize an entire mission. By extracting the space information form sensors, an AUV can achieve the localisation and mapping which are currently two primary concerns in the robotics research. Meanwhile, such information will provide a fundament of protection for surface vessels or troops, harbour infrastructure and oil plant against the enemy and terrorism. Acoustic sensors are commonly used to detect and position underwater obstacles, suspicious objects or to map the surroundings because sound waves can propagate more appreciable distances than electromagnetic and optical energy in the water. The measurements from these sensors, however, are always bound up with noises and errors. Various underwater activities may further pollute sound signals and then threaten the AUV navigation process. To simplify the detection procedure, some researchers make use of acoustic beacons or apparent obstructions (such as rocks, concrete walls) because they have distinctive characteristics. Point or line features are extracted from the acoustic signals or images for localization and mapping purposes. The long propagation range of sound waves can present new problems when acoustic sensors operate in confined environments, such as water tanks, rivers and harbours. The multiple reflections will be recorded by the sensor and result in false alarms. Furthermore, with advances in manufacturing techniques, the downsizing in marine explosive ordnances is progressing significantly, making it more difficult to discriminate between surface reflections and explosive ordnances. Finally, under the consideration of cost effectiveness, a mechanically scanned sonar has been introduced for the AUV in this research. However, the sensor beam cannot cover a large region simultaneously and a moving object may be distorted in the acoustic image because of the relatively low scanning speed. Due to such distortions in the data flows, objects may be indistinguishable from random noise or reverberation in acoustic images. The research presented here addresses the afore-mentioned problems relating to the theme of automatic detection from acoustic images. It is concerned with the detection and tracking of small underwater objects in order to protect autonomous underwater vehicles using sonar (SOund Navigation and Range). In the present study, these vehicles operated in laboratory water tanks or natural river environments. This research made use of self provided analytical studies that differentiated between reverberation and real object echoes. Detections were achieved automatically by using signal and image processing techniques. This research consists of three important and linked strategies. Firstly, a simple and fast reverberation suppression filter was provided, based on the understanding of the mechanism of the sonar sensor. Secondly, a robust detection system was developed to perceive small suspended obstacles in the water. Thirdly and finally, arc features were successfully extracted from the acoustic images and mathematical maps were generated from those features. The majority of experiments were derived from the elliptical water tank and the River Torrens, Adelaide, South Australia. For this project, a sequence of sonar images was taken from the same sonar location in the elliptical water tank. Further, a sequence of sonar images was taken from a sequence of sonar locations in the natural river. They provided different data sets for the assessment and evaluation of self developed algorithms. Results shown in this thesis confirm the favourable outcomes of the investigation and applied methodology.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1454839
Thesis (M.Eng.Sc.) -- University of Adelaide, School of Mechanical Engineering, 2010

This thesis investigates the improvements that can be made to Bayesian passive sonar tracking in the context of active-passive sonar data fusion. Performance improvements are achieved by exploiting the prior information available within a typical Bayesian data fusion framework. The algorithms developed are tested against both simulated data and data measured during the SEABAR 07 sea trial. Results show that the proposed approaches achieve improved detection, decreased estimation error, and the ability to track quiet targets in the presence of loud interferers.
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In this dissertation an innovative technology to study whale sharks, Rhincodon typus is presented. The Integrated Satellite and Acoustic Telemetry project (iSAT) combines underwater acoustic telemetry, autonomous navigation and radio frequency communications into a standalone system. The whale shark, a resident of the Saudi Arabian Red Sea, is the target of the study. The technology presented is designed to help close current gaps in the knowledge of whale shark biology; these are gaps that prohibit the design of optimal conservation strategies. Unfortunately, the various existing tracking technologies each have limitations and are unable to solve all the unanswered questions. Whale shark populations are increasingly threatened by anthropogenic activities such as targeted and indirect fishing pressure, creating an urgent need for better management practices. This dissertation addresses the current state-of-the-art of relevant technologies, including autonomous surface vehicles (ASVs), sensors for research in the ocean and remote monitoring of wild fauna (biotelemetry). iSAT contains components of all of these technologies, but the primary achievement of this dissertation is the development of iSAT’s Acoustic Tracking System (ATS). Underwater, the most efficient way of transmitting energy through long distances is sound. An electronic tag is attached to an animal and works as its acoustic identifier. iSAT’s hydrophone array detects the presence and direction of the acoustic signal generated by the tag. The expected performance, range, and capacity to tell the direction to the tag are explained and compared to the actual measured values. The first operational iSAT ATS is demonstrated. This work represents significant advancement towards a fully autonomous iSAT system. Developments on the power electronics, navigation, renewable energy harvesting, and other modules are included in this research. With the recent integration of digital acquisition systems, iSAT’s capabilities were increased to minimize its size and allow it to communicate with other acoustic systems. Future engineering works are still necessary to achieve a fully automated system, but the current developments with the ATS have immediate applications.

Tracking multiple targets in a high cluttered environment where multiple receivers are used is a challenging task due to the high level of false alarms and uncertainty in the track hypothesis. The multi-static active sonar scenario is an example for such systems where multiple source-receiver combinations are deployed. Due to the nature of the underwater environment and sound propagation characteristics, tracking targets in the underwater environment becomes a complex operation. Conventional tracking approaches (such as the Kalman and particle filter) require a predetermined kinematic model of the target. Moreover, tracking an unknown and changing number of targets within a certain search area requires complex mathematical association filters to identify the number of targets and associate measurements to different target tracks. As the number of false detections increases, the computational complexity of conventional tracking system grows introducing further challenges for real-time target tracking situations. The methodology presented in this thesis provides a rapid and reliable tracking system capable of tracking multiple targets without depending on a kinematic model of the target movement. In this algorithm, Self Organizing Maps, Dynamic Programming and the Hough transform are combined to produce tracks of possible targets’ paths and estimate of targets’ locations. Evaluation of the performance of the tracking algorithm is performed using three types of simulations and a set of real data obtained from a sea trial. This research documents the results of experimental testing and analysis of the tracking system.
Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2009-08-07 13:21:06.869

Autonomous underwater vehicles (AUVs) have been increasingly applied to oceanographic missions. Despite technological advances, adaptability to environmental changes or intelligent behaviour is still at an early stage of development, especially for large survey class AUVs. This research addresses the real-world challenge of using an AUV to delineate an oil plume in sea water, in the management of an environmental spill. A review of current literature showed the most common methodology in conventional adaptive AUV missions involved gradient-following methods with point-based sensors such as fluorometers. In this work, an adaptive sampling algorithm was developed for real discontinuous oil plumes and validated through simulation, The search and detection phase of the algorithm was tested through ocean trials with an Explorer survey-class AUV. In order to develop the algorithm, I complete a series of preparatory tests in a seawater tank, the ocean and in a lake. I used a seawater tank to assess the formation of oil in seawater, waves and currents and to assess the utility of sonar as a sensor for these oil droplets. The ocean was investigated to try to find an environment to test an AUV in an area of naturally occurring oil seeps. Finally, a lake was used to assess different proxies to represent oil in the ocean in order to avoid environmental damage and to obtain sonar records for use in developing real time analysis methods. The oil formation tests showed that real oil plumes are composed of countless undissolved droplets, especially after exposure to waves and currents. This result focused attention on the critical need for a sensor that could identify oil plumes at distance and a sampling strategy that could take into account the coalescent and clustering characteristics of real oil droplets in the water column. The seawater tank experiment found that a higher frequency sonar (1.35 MHz) was more effective than a lower frequency sonar (450 kHz) in capturing an oil plume in the water column. Thereafter, a scanning sonar (750 kHz frequency) was proposed as the primary sensor on the AUV in searching for plumes. An adaptive sampling mission can be achieved by utilising real-time processing of in-situ data to optimise an AUVs capability to complete a task, Here I developed modular algorithms for acoustic detection and in-situ analysis. In accordance with the use of sonar as an oil detection sensor, I introduced a new search path inspired by bumblebee flight patterns and validated this through field trials. This search design significantly improved the more conventional survey plans based on lawnmower paths by reducing the time to seek an oil plume by approximately 75.3%. For the detection strategy, the key assumption was to approximate an oil plume in a two-dimensional sensing layer with limited vertical extent. This improved detection performance by using a higher order two-dimensional scanning method that minimised the plausible impacts of mixing energies on the plume. A ‘Measure – Analysis – Action’ schema was employed in a recursive algorithm for oil plume tracking. The tracking modules analysed the recovered sensor data in real time to produce the desired best new heading of the AUV. To produce the best tracking performance, all the relevant parameters of each component term of the algorithm (such as thresholds, coefficients and weighting factor) had to be tuned and adjusted. Thereafter, I was able to track different forms of simulated oil plumes successfully with the AUV. The search and detection algorithms, as well as the backseat driver control system of the AUV using MOOS IvP routines (some of which I developed), were tested on the Explorer AUV during in ocean trials in Holyrood Bay, Newfoundland and Labrador, Canada. The algorithm implemented on the real AUV successfully demonstrated the AUV backseat driver control. Having appropriate configuration parameters, the guided path could be followed through updating the AUV state in pose (translational position (x, y) and rotational (θ) angle). AUV heading direction was corrected by adapting to the computed desired heading, which was achieved in 2.8 seconds on average after the command was generated. Overall, the vehicle trajectory remained within 5.5m of the guided path. The field experiments verified the feasibility and utility of the designed search and detection algorithm in the ocean environment. Overall, this research has overturned the most common gradient-following methods employed in AUV-based oil spill investigation and tracking. The adaptive sampling system developed in this thesis provides an efficient tool to i) seek a realistic oil plume whose chemical characteristics may have altered over time, ii) detect patches of the plume with varying shapes and density and iii) track and map a plume without losing contact with it. The knowledge obtained through this research and the presented algorithm modules will support the next generation of researchers seeking to advance the autonomy of AUVs.

碩士
環球科技大學
環境資源管理所
101
Abstract This study aimed to develop a low cost buoyant solar tracking system, in order to enhance the efficiency of solar power generation. The buoyant solar tracking system contains two main modules. One is the automation photosensitive module consisting of the photosensitive element and automation control circuit of the control module; the other is buoyant module with water pumps and the leveling mechanism including buoyant balls. This design begins with the capture of sunlight by the photosensitive element, which passes over the signal to the automation module to control the water pumps, resulting in the difference of water levels in the East and West. The differential buoyancy causes the solar photovoltaic panels to synchronize with the angle of solar position, optimizing the power generation. Test results showed that the system can improve of 37.67% of the power generation of the solar cell panel.

碩士
國立臺灣大學
機械工程學研究所
96
The research develops a more economizing solar tracker. By simulation sun focusing trajectory as a special curve, the design of Focusing Trajectory Tracking Solar Collector is established based on the curve shape. The system contains: GaAs solar cell, focusing trajectory mechanism, Fresnel lens, a stepping motor and its driver, photosensitive resistors, switches, and a microcontroller PIC18F4480. The following is features of the tracking solar collector. (1) Due to the design of focusing trajectory mechanism, one dimension move of the stepping motor can drive two dimension movement of the solar cell. (2)There is a Fresnel lens to concentrate light, but the motor is unnecessary to drive both lens and solar cell, just drive small and light solar cell. This design can substantially reduce power consumption of the motor. (3)Using photosensitive resistors as sensors in accordance with focusing trajectory tracking solar collector looks for a tracking logic to track the Sun.

碩士
國立臺北科技大學
能源與冷凍空調工程系碩士班
99
With the increasing awareness of sustainable and green building, more and more people are concerned with the efficiency of energy use at home and at work. A solar tracking skylight illumination system, which enables us to conserve energy by producing increased interior light levels for a longer duration than normally possible, can fit to the above need and have widen been used in the indoor illumination gradually. In this study, an experimentally investigation is conducted to explore the dynamic illuminative performance of solar tracking skylight illumination system. In the first stage of this research, a tracking skylight illumination system is tried to be developed by implement. In the second stage, the experimental test apparatus is set up and the basic lighting intensity distribution of skylight illumination system will be examined. In addition, the effects of various design parameters, e.g., the material of reflective panel and diffusive panel, the sensitivity of tracking skylight illumination system and skylight condition, are also analyzed. The results show that (1) The maximum amount of deviation of this solar-tracking system was found to be up to 10° from the accurate sun path through the whole year, which results in 18% decay in lighting intensity；(2) Illumination of indoor lighting is 10% (100W) of outdoor solar radiation intensity; (3) A set of solar-tracking skylight system can save electronic power about 292 kw-hr per year.

碩士
國立臺灣大學
機械工程學研究所
98
The research develops a more robust solar tracker. Simulation shows that focusing trajectory of sun rays of four seasons form a special surface. Thus, a steric focal trajectory tracking solar collector is designed. The system contains a GaAs solar cell, a focusing trajectory mechanism, Fresnel lens, three stepping motors with their drivers, six limiting switches, and a microcontroller PIC18F4520. The tracking solar collector has the following features: (1) A Fresnel lens to concentrate light which lets the solar cell absorb more energy. The lens is kept fixed without the need to move or rotate, but instead, the solar cell with relative small size and light weight is driven by the motor. This design can reduce power consumption of the motor. (2) It can automatically find a non-circle focal point in the space. (3) Vertical design allows it to be put on the wall of a building. The efficiency of this solar cell system at noon is of about 0.21％ to 0.81% . It can be compared to a system fixed on the wall which is of about 1.03% to 2.48%. The efficiency of this solar cell system at sunset is of about 1.70% to 2.47% and can be compared to a system fixed on the wall which is of about 0.52% to 0.78%. The reason is that the energy of light focused through the lens is less at noon than at sunset when the Fresnel lens is placed vertical. This system’s concentration factor is 507, so it is capable of decreasing 99.8 percent of the solar cell’s area to achieve comparable system efficiency and therefore, the cost of this system can be reduced.

碩士
環球科技大學
環境資源管理所
102
Renewable energy has become an important part of the global energy structure, under the pressure of greenhouse gas (GHGs) reduction. Solar tracking system is especially important. However, there is still room for improvement for the collimator used in the closed-loop tracking system. Therefore, this study aims to design a simple dual-axis tracking device, which consists of a collimator made of Fresnel lens and optic fiber that links to the control units. Our discoveries include 1. The use of one spiral and one linear Fresnel lens turns the incoming light into a narrow stripe, which is totally different from a dot or spot found in patents and literature. 2. The front end of the optic fiber is placed where the stripe is and the rear end is linked to the light detecting resistors (LDRs) and control units; thus, and contamination and ageing due to exposure of the LDRs to the exterior environment is prevented. 3. Modulation of the device helps the maintenance work later. 4. The field measurements show that our device can achieve the tracking precision within three degrees; under a sunny day, the power generation can be increased up to 37.4% compared with fixed solar panels. Our suggestions include 1. To develop customized Fresnel lens in order to reduce the size of the collimator. 2. To integrate with automation circuit or other methods to improve precision that a low concentration photovoltaic (LCPV) system requires.

碩士
國立高雄應用科技大學
電機工程系
99
Few solar energy collecting devices now available are satisfactory in performance ; due to the capability for tracking the sun is limited to its fixed position, which decreases the efficiency in energy use, and extra expense is cost if a motor-propelled device is installed. This research presents a magnet-propelled solar tracking device, in which the characteristic of magnet and circuit theory is applied. This device will increase the efficiency in solar cell use and reduce waste during sun tracking.

碩士
國立中興大學
機械工程學系所
107
How to improve the photoelectric conversion efficiency of solar cells and the solar tracking technology, are very important for technological development of solar power generation. About patent analysis in solar energy applications, there are many researches on solar cells more than solar tracking technology. According to searches、integrates and analyzes from the patents of solar tracking technology, the development and design of the solar tracking system is quite actively, but development pace of the maximum power point tracking rule and the the solar tracking mechanism are slowing down.Wherein, some patents mention that the solar tracking can be implemented without electric motors, and to achieve energy saving and environmental protection. Patent qualitative analysis is also used to analyzes a patent case in this paper, this is much different from the current patent analysis model based on quantitative analysis.

碩士
國立交通大學
電控工程研究所
105
MPPT technique is often used in PV systems to solve low efficiency problem in energy conversion which is deeply affected by surroundings. In MPPT, methods based on the concept of P&O are very popular since their algorithms are simple and easy to implement. However, this kind of methods has a slower response and often encounters severe oscillation during steady status. Such oscillation causes the average output power level deviated from MPP and makes the voltage chattering around MPP. Therefore, this thesis proposes a FLC method to improve the above shortcomings. Simulation results show that the FLC not only has a fast response, but also eliminates the oscillation to keep the output power steady and smooth the voltage without chattering. Similar to the simulation, the experimental results show that the FLC can fast drive the system to MPP in 5 seconds and highly reduce the oscillation so that the ratio of voltage chattering is below 1%. In addition, this thesis uses the compass sensor and solar trajectory to set up a dual-axis solar tracking system. A simple sundial used to check the angle between the solar panel and sunlight is less than 5 degrees in most of the day, which implies a good performance of solar tracking.

The DLOOP is a structure of non-overlapping tiles (typically corner connected) occupying two layers. Interest in the DLOOP arises from Photo-Voltaic (PV) tracking applications. The tiles (PV modules) of contemporary tracking systems are within one contiguous layer, i.e. a side-by-side platform (SSP). Trees collect solar energy using branching structures to support leaves which are, similar to PV modules, planar surfaces of solar energy transformation. The tree's form is naturally excellent for lowering structural stress in limbs and thermal stress in leaves. For analogous reasons, related to the creation of flow paths that would otherwise be blocked, this research hypothesised (and has subsequently shown) that: * the fluid (wind) dynamic force on tiles of high inclination SSP may be reduced (up to 30%) adopting DLOOP arrangements; and * the temperature of heated tiles in SSP may be reduced (up to 5K within nominal and hot terrestrial environments), by passive convective cooling, adopting DLOOP arrangements. Fluid (wind) dynamic force is significant in PV applications because it typically exceeds the force of gravity on the tiles of SSP in 13m/s winds and increases with velocity squared. Hence reducing wind force by 30% should allow 40% more tiles to be fitted to contemporary tracking mechanisms. Temperature is significant in PV applications because the performance of PV tiles typically falls 0.4%/K. Hence a 5K reduction in temperature should improve efficiency 2%. A combination of wind-tunnel tests, Particle Image Velocimetry and Computational Fluid Dynamic (CFD) simulations using Reynolds Averaged Navier Stokes and Large Eddy Simulation turbulence models was used for the fluid dynamic research. A combined Finite Element/CFD simulation of PV panels in platforms was developed to model temperature outcomes of thermal diffusion in solid materials and thermal diffusion, radiation and convection in the fluid (air). If PV-tracking ranges are limited below those of the solar-vector, shading of the DLOOP lower by the upper layer occurs. This DLOOP self-shading raises unique cost-benefits associated with tracking ranges. Consequently, this research develops a means to quantify the insolation received by platforms accounting for technology and tracking range in diverse (Australian) climates. Additionally, multiple tracking platforms may be placed in close proximity and suffer "Parasitic" energy losses when shaded by self-similar neighbours. Therefore, this research study introduces a natural no-shade scale to describe and optimise field layouts according to local insolation and economic conditions.

碩士
崑山科技大學
機械工程研究所
96
In order to ameliorate available solar dryer systems and reduce disadvantagescoming from normal structures, a new design of solar dryer system has been investigated in Mechanical Engineering Department of Kun Shan University of Technology, Taiwan - R.O.C. The system only consists of a collector - chamber and a rotatable reflector which are designed for drying food products. Performance characteristic of the new design shows a high ability of being used by customers for its better drying parameter values compared to those of previous systems. It has been successfully tested in unload mode. Experiments have been performed to investigate the performance evaluation & drying behavior of the system. In comparison with an available solar drying system in Kun Shan University, this new solar dryer is offering a range of temperature closer to desired temperature of specific products (with the same air mass going through chamber) which leads to shorter time of drying. Besides, new structure also helps to solve some disadvantages of previous one such as heat loss, working period, troubles caused by dust in air …