On Reliability of Underwater Magnetic Induction Communications with Tri-Axis Coils

Underwater magnetic induction communications (UWMICs) provide a low-power and high-throughput solution for autonomous underwater vehicles (AUVs), which are envisioned to explore and monitor the underwater environment. UWMIC with tri-axis coils increases the reliability of the wireless channel by exploring the coil orientation diversity. However, the UWMIC channel is different from typical fading channels and the mutual inductance information (MII) is not always available. It is not clear the performance of the tri-axis coil MIMO without MII. Also, its performances with multiple users have not been investigated. In this paper, we analyze the reliability and multiplexing gain of UWMICs with tri-axis coils by using coil selection. We optimally select the transmit and receive coils to reduce the computation complexity and power consumption and explore the diversity for multiple users. We find that without using all the coils and MII, we can still achieve reliability. Also, the multiplexing gain of UWMIC without MII is 5dB smaller than typical terrestrial fading channels. The results of this paper provide a more power-efficient way to use UWMICs with tri-axis coils

Node localization in underwater sensor networks (UWSN)

This dissertation focuses on node localization in underwater wireless sensor networks (UWSNs) where anchor nodes have knowledge of their own locations and communicate with sensor nodes in acoustic or magnetic induction (MI) means. The sensor nodes utilize the communication signals and the locations of anchor nodes to locate themselves and propagate their locations through the network. For UWSN using MI communications, this dissertation proposes two localization methods: rotation matrix (RM)-based method and the distance-based method. Both methods require only two anchor nodes with arbitrarily oriented tri-directional coils to locate one sensor node in the 3-D space, thus having advantages in a sparse network. Simulation studies show that the RM-based method achieves high localization accuracy, while the distance-based method exhibits less computational complexity. For UWSN using acoustic communications, this dissertation proposes a novel multi-hop node localization method in the 2-D and 3-D spaces, respectively. The proposed method estimates Euclidean distances to anchor nodes via multi-hop propagations with the help of angle of arrival (AoA) measurements. Simulation results show that the proposed method achieves better localization accuracy than existing multi-hop methods, with high localization coverage. This dissertation also investigates the hardware implementation of acoustic transmitter and receiver, and conducted field experiments with the hardware to estimate ToA using single pseudo-noise (PN) and dual PN(DPN) sequences. Both simulation and field test results show that the DPN sequences outperform the single PNs in severely dispersive channels and when the carrier frequency offset (CFO) is high --Abstract, page iv

Smart marine sensing systems for integrated multi-trophic aquaculture (IMTA)

Aquaculture farming faces challenges to increase production whilst maintaining sustainability by reducing environmental impact and ensuring efficient resource usage. One solution is to use an Integrated Multi-Trophic Aquaculture (IMTA) approach, where a variety of different species are grown in the same site, taking advantage of by-products (such as waste and uneaten food) from one species as inputs (fertilizer, food, and energy) for the growth of other species. However, the remote monitoring of environmental and biological conditions is crucial to understand how the species interact with each other and with the environment, and to optimise the IMTA production and management system. Environmental monitoring of aquatic environments is already well supplied by commercial off-the-shelf sensors, but these sensors often measure only one parameter, which increases the power consumption and cost when monitoring multiple environmental variables with a fine-scale resolution. Current monitoring solutions for seaweed and kelp also include satellite and aerial sensing, which cover large areas effectively. However, these methods do not offer high-resolution, specific local data for growing sites, and are usually limited by turbidity and weather conditions. Another limitation of available commercial systems is data recovery. Most of them require that the sensor be retrieved to download data directly, increasing cost of maintenance. Radio Frequency Identification (RFID) systems that transmit in the near field (Near Field Communication – NFC) are less attenuated by the seawater environment than higher-frequency communications, and thus potentially provide a more viable alternative for underwater data transmission. In this work, we present a novel miniature low-power multi-sensor modality NFC-enabled data acquisition system to monitor a variety of farmed aquaculture species. This sensor system monitors temperature, light intensity, depth, and motion, logging the data collected internally. The sensor device can communicate with NFC-enabled readers (such as smartphones) to configure the sensors with custom sampling frequencies, communicate status, and to download data. It also has an internal machine learning enabled microcontroller, which can be used to perform data analysis internally. The device is designed to be attachable to seaweed and kelp blades or stipes. The system designed was tested in lab to characterise its sensors and to determine its battery lifetime. The sensor device was then deployed in an IMTA farm in Bertraghboy Bay, Connemara, Ireland, with the help of the Marine Institute. The data collected from the device was then correlated with environmental sensors placed in the site. Future work involves incorporating data analytics and machine learning algorithms to process data internally, allowing for lower transmission requirements

Machine Learning-Based Prediction of Node Localization Accuracy in IIoT-Based MI-UWSNs and Design of a TD Coil for Omnidirectional Communication

This study aims to realize Sustainable Development Goals (SDGs), i.e., SDG 9: Industry Innovation and Infrastructure and SDG 14: Life below Water, through the improvement of localization estimation accuracy in magneto-inductive underwater wireless sensor networks (MI-UWSNs). The accurate localization of sensor nodes in MI communication can effectively be utilized for industrial IoT applications, e.g., underwater gas and oil pipeline monitoring, and in other important underwater IoT applications, e.g., smart monitoring of sea animals, etc. The most-feasible technology for medium- and short-range communication in IIoT-based UWSNs is MI communication. To improve underwater communication, this paper presents a machine learning-based prediction of localization estimation accuracy of randomly deployed sensor Rx nodes through anchor Tx nodes in the MI-UWSNs. For the training of ML models, extensive simulations have been performed to create two separate datasets for the two configurations of excitation current provided to the Tri-directional (TD) coils, i.e., configuration1-case1_configuration2-case1 (c1c1_c2c1) and configuration1-case2_configuration2-case2 (c1c2_c2c2). Two ML models have been created for each case. The accuracies of both models lie between 95% and 97%. The prediction results have been validated by both the test dataset and verified simulation results. The other important contribution of this paper is the development of a novel assembling technique of a MI-TD coil to achieve an approximate omnidirectional magnetic flux around the communicating coils, which, in turn, will improve the localization accuracy of the Rx nodes in IIoT-based MI-UWSNs

Permanent Magnet Linear Generators for Marine Wave Energy Converters

Abstract: Direct drive Permanent Magnet Linear Generators (PMLGs) are used in energy converters for energy harvesting from marine waves. Greater reliability and simplicity can be achieved for Wave Energy Converters (WECs), by using direct drive machines linked to the power take-off device, in comparison with WECs using rotational generators combined with hydraulic or mechanical interfaces to convert linear to rotational torque. However, owing to the relatively low velocities of marine waves and the desire for significant energy harvesting by each individual unit, direct drive PMLGs share large permanent magnet volumes and hence, high magnetic forces. Such forces can generate vibrations and reduce the lifetime of the bearings significantly, which is leading to an increase in maintenance costs of WECs. Additionally, a power electronics converter is required to integrate the generator‘s electrical output to meet the requirements for connection to the national grid. This thesis is concerned mainly with the fundamental investigation into the use PMLGs for direct drive WECs. Attention is focused on developing several new designs based on tubular long stator windings topologies and optimisation for flat PMLGs. The designs are simulated as air- and iron-cored machines by means of Finite Element Analysis (FEA). Furthermore, a new power electronics control system is proposed to convert the electrical output of the long stator generators. Various wave energy-harvesting technologies have been reviewed and it has been found that permanent magnet linear machines demonstrate great potential for integration in WECs. The main reason is the strong exaltation flux provided by the high number of permanent magnets. Such flux, combined with design simplicity, can deliver high induced voltage as well as structural integrity. In the thesis, a flat single and double structured iron-cored PMLG is studied and optimised. Several magnetic force mitigation techniques are investigated and an optimisation is conducted. The optimisation is concerned mainly with increasing electrical output power and reducing the magnetic forces in the generators. As a result, an optimal design introducing the idea of separated magnetic cores has been proposed. The FEA simulations reveal that magnetic separation in the yoke can increase significantly the energy-harvesting capability of PMLGs. Furthermore, the concept of the design of long stator windings for tubular PMLGs is studied. Two long stator generators having different magnetisation topologies and similar sizes to existing machine are modelled and compared to the existing machine. The similar-sized existing and proposed PMLGs are simulated by FEA. In this way, settings such as different boundary conditions, symmetry boundaries and material properties are used to gain confidence in the simulated results of the proposed machines. Moreover, the simulated results for the existing PMLG are verified against previously performed numerical simulations and practical tests delivered and published as part of other research. The outcome for the proposed PMLGs reveals several advantages for the long stator design, such as lower cogging forces and higher energy harvesting and a lower price of the raw structural materials. Additionally, the thesis proposes and simulates a new design for an air-cored PMLG. To boost the output power, the proposed design is based on a long stator topology adopting two sets of permanent magnet rings sandwiching copper windings in a tubular structure. The design is compared with a current machine in FEA and the results show significant reduction in radial forces and an increase in energy harvesting. Finally, a novel power electronics control system, bypassing inactive coils is suggested and simulated as part of the grid integration system for the long stator PMLGs. The new system achieves a reduction in the thermal losses in the power electronics switches in comparison with existing systems. The power electronics system and the generator have been simulated in Matlab coupled externally with FEA (JMAG Designer).PRIMaRE/University of Exete

Space weather instruments and measurement platforms

Avaruussää on Maapallon lähiavaruuden ilmiö. Sillä on useita ilmenemismuotoja, joista tunnetuin on revontulet. Avaruussää aiheuttaa haittaa kriittisille infrastruktuureille, kuten satelliiteille ja sähköverkoille. Tämän diplomityön tarkoituksena on tutkia nykyisiä avaruussääinstrumenttejä sekä mittausjärjestelmiä ja kartoittaa niiden toimintakyky sekä heikkouksia. Magnetometri-, ionosfääri, aurinkotuuli- ja Aurinkoinstrumentaatiolle ja järjestelmille suoritetaan kattava analyysi. Lopputulokset osoittavat että nykyiset instrumentit kykenevät mittaamaan kaikkia avaruussäähän liittyviä ilmiöitä. Magnetometrimittausten peitto revontuliovaalilla ei ole riittävä tarkkaan avaruussäätutkimukseen, sillä magneettikenttää ei kyetä mittaamaan merellä. Ionosfäärimittauksilla on samanlaisia ongelmia maantieteellisen peiton kanssa ja niistä on saatavilla lyhyempiä aikasarjoja. Aurinko- ja aurinkotuulimittaukset ovat keskittyneet pienelle määrälle satelliitteja jotka ovat kalliita ja hankalia korvata. Lopputuloksina suositellaan CubeSat-satelliittien kyytiin asennettavien magnetometrien testausta, vedenalaisten magnetometrien käyttöönottoa sekä parannuksia ionosfäärin ja magnetosfäärin mittauspeitossa. Kykyä suorittaa jatkuvia Aurinko- ja aurinkotuulimittauksia avaruuteen sijoitetuilla järjestelmillä pitäisi myös ylläpitää.Space weather is a phenomenon affecting near-Earth space. It manifests itself in numerous different ways, the best known being the Aurora. Space weather causes numerous problems to several critical infrastructures, such as power grids and satellites. This master’s thesis investigates current space weather instrumentation and systems to analyze their capabilities and possibly existing gaps in measurements. Analysis of magnetospheric, ionospheric, solar and solar wind instruments and instrument platforms is conducted. Our results show that currently existing instrumentation is able to measure essentially all space weather phenomena. Magnetometer coverage in auroral regions is not sufficient for detailed space weather analysis e.g. due to the lack of capability for measuring magnetic field at the sea. Ionospheric measurements have similar problems with coverage, but they also have rather short time series. Solar and solar wind observations are concentrated on a small number of orbital observatories that are difficult to replace and expensive. In conclusion, testing of CubeSat mounted fluxgate magnetometers, adoption of underwater magnetometers and improvements in coverage of ionospheric and magnetospheric measurements are suggested. Maintenance of the ability to conduct in situ measurements of solar wind and and solar observations are recommended

Advances in Intelligent Robotics and Collaborative Automation

This book provides an overview of a series of advanced research lines in robotics as well as of design and development methodologies for intelligent robots and their intelligent components. It represents a selection of extended versions of the best papers presented at the Seventh IEEE International Workshop on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications IDAACS 2013 that were related to these topics. Its contents integrate state of the art computational intelligence based techniques for automatic robot control to novel distributed sensing and data integration methodologies that can be applied to intelligent robotics and automation systems. The objective of the text was to provide an overview of some of the problems in the field of robotic systems and intelligent automation and the approaches and techniques that relevant research groups within this area are employing to try to solve them.The contributions of the different authors have been grouped into four main sections:• Robots• Control and Intelligence• Sensing• Collaborative automationThe chapters have been structured to provide an easy to follow introduction to the topics that are addressed, including the most relevant references, so that anyone interested in this field can get started in the area