Replacing humans with underwater robots for accomplishing marine tasks such as oceanic supervision and undersea operations have been an endeavour from long time ago. Hence, a number of underwater robots have been developed. Among those underwater robots, developing biomimetic swimming robots has been appealing for many researchers and institutes since these robots have shown superior performance. Biomimetic swimming robots have higher swimming efficiency, manoeuvrability and noiseless performance. However, the existing biomimetic swimming robots are specialised for a single gait of locomotion like cruising, manoeuvrability and accelerating while for efficient accomplishment of marine tasks, an underwater robot needs to have multiple gaits of locomotion. In order to develop multiple-gaited swimming robots, the optimal characteristics of each gait of swimming must be combined together, whereas the combination is not usually possible. The problem needs to be addressed during the design process. Moreover, the optimality of the actuation mechanism of robots - that do not utilise any artificial muscle - could be assured using the mathematical model employed for simulation of their swimming behaviour. However, the existing models are incomplete and, accordingly, not reliable since their assumptions like the constant speed of flow around the fish robot could be used when the average speed of the flow is determined during experiment while before development of robots, the flow speed is not known. In addition to that, the simulation results must be optimised using the experimental observations in nature and analytical results while the optimisation algorithms are based on one fitness function. The aforementioned problems as well as the fabrication challenges of free-swimming biomimetic robots are addressed in a development process of multiple-gaited fish-mimetic robots introduced by the author in this thesis. This development method engages the improvement of all development steps of fish robots including design, mathematical modelling, optimisation and fabrication steps. In this thesis, the aforementioned steps are discussed and the contributions of the method for each step are introduced. As an outcome of the project, two prototypes of fish robots called UC-Ika 1 & 2 are built.

Approved for public release; distribution is unlimited / Unmanned vehicle technology has matured significantly over the last two decades. This is evidenced by its widespread use in industrial and military applications ranging from deep-ocean exploration to anti-submarine warefare. Indeed, the feasiblity of short-range, special-purpose vehicles (whether aunonomous or remotely operated) is no longer in question. The research efforts have now begun to shift their focus on development of reliable, longer-range, high-endurance and fully autonomous systems. One of the major underlying technologies required to realize this goal is Artificial Intelligence (AI). The latter offers great potential to endow vehicles with the intelligence needed for full autonomy and extended range capability; this involves the increased application of AI technologies to support mission planning and execution, navigation and contingency planning. This thesis addresses two issues associated with the above goal for Autonomous Underwater Vehicles (AUV's). Firstly, a new approach is proposed for path planning in underwater environments that is capable of dealing with uncharted obstacles and which requires significantly less planning time and computer memory. Secondly, it explores the use of expert system technology in the planning of AUV missions.

Devido à grande importância do ambiente aquático sobre a vida humana e às dificuldades inerentes ao seu estudo e exploração, a aplicação de AUVs tem se mostrado bastante benéfica e seu uso vem crescendo ao longo dos anos. Este trabalho apresenta um estudo sobre o desenvolvimento de veículos autônomos submarinos para realização de missões oceanográficas, com foco nas características de seus sistemas embarcados que permitam atender melhor os requisitos desta aplicação. Analisando trabalhos publicados nos últimos anos pode-se notar uma grande quantidade de AUVs desenvolvidos ou adaptados para aplicações em oceanografia, com uma grande variedade de soluções aplicadas em seus diversos sistemas, visando a realização de diversos tipos de missões necessárias para tais estudos. Como estudo de caso, foi apresentada a adaptação do AUV Pirajuba, desenvolvido inicialmente como uma plataforma de testes hidrodinâmicos, para aplicação em missões de levantamento de dados para estudos oceanográficos. Para tal, foi necessário realizar uma série de modificações em seus subsistemas, permitindo a instalação de novos sensores e equipamentos para aumento da segurança nas operações em mar aberto. As modificações necessárias envolveram tanto o sistema hidromecânico do veículo, com instalação de novos módulos no casco, quanto no seu sistema embarcado, implicando no desenvolvimento de uma nova versão do sistema de hardware e uma atualização no software de controle. Tendo em vista esta necessidade, foi proposto um estudo dos requisitos da aplicação oceanográfica de AUVs e os impactos no seu desenvolvimento. Para isso, foi realizado um levantamento dos requisitos das principais aplicações oceanográficas e seus impactos no desenvolvimento dos veículos, envolvendo os sistemas hidromecânico, energia, navegação, comunicação e controle. Foi realizado também um estudo da arquitetura de controle CANARMES, desenvolvida para o AUV Pirajuba, envolvendo os requisitos de seu projeto e as principais características da arquitetura de controle, que serviu como base para a atualização do veículo para as novas aplicações. São apresentados os resultados obtidos em testes de campo realizados no litoral de Ubatuba - SP, nos quais foram feitas manobras com movimentação vertical com a aquisição de dados de diversos sensores oceanográficos, utilizados para o estudo de detecção de camadas finas. / Due to the great importance of the aquatic environment on human life and the inherent difficulties of its study and exploration, the application of AUVs has been shown to be very beneficial and its use has been growing over the years. This work presents a study on the development of autonomous submarine vehicles for the accomplishment of oceanographic missions, focusing on the characteristics of the embedded systems of these vehicles in order to better meet the application requirements. Analyzing published works in the last five years, it can be noticed a great amount of AUVs developed or adapted for applications in oceanography, with a great variety of solutions applied in their embedded systems, involving both hardware and software, aiming at the accomplishment of several types of missions necessary for such studies. As a case study, the adaptation of the AUV Pirajuba, initially developed as a platform for hydrodynamic tests, was presented for application in data collection missions for oceanographic studies. For this, it was necessary to make a series of modifications in its subsystems, allowing the installation of new sensors and equipment to increase the safety in the operations in the open sea. The necessary modifications involved both the vehicle\'s hydromechanical system, with the installation of new modules in the hull, and in its embedded system, requiring the development of a new version of the hardware system and an update in the control software. Due to this necessities, a study was proposed to better understand the requirements of AUVs for oceanographic application and the impacts on their development. For that, a survey was made of the requirements of the main oceanographic applications and their impacts on the development of the vehicles, involving the hydromechanical, energy, navigation, communication and control systems. A study of the CANARMES control architecture, developed for the Pirajuba AUV, was carried out, involving the requirements of its design and the main characteristics of the control architecture, which served as a basis for updating the vehicle for new applications. We present the results obtained in field tests conducted in the coastal area of Ubatuba - SP, Brazil, in which maneuvers were performed with vertical movement, while acquiring data from several oceanographic sensors, used for the study of thin layer detection.

A tarefa de operar um veículo submarino durante missões de inspeção de ambientes estruturados como, por exemplo, duto de usinas hidrelétricas, é feita principalmente por meio de referências visuais e uma bússola magnética. Porém alguns ambientes desse tipo podem apresentar uma combinação de baixa visibilidade e anomalias ferromagnéticas que inviabilizaria esse tipo de operação. Este trabalho, motivado pelo desenvolvimento de um veículo submarino operado remotamente (ROV) para ser usado em ambientes com essas restrições, propõe um sistema de navegação que utiliza o conhecimento prévio das dimensões do ambiente para corrigir o estado do veículo por meio da correlação dessas dimensões com os dados de um sonar de imageamento 2D. Para fazer essa correlação é utilizado o ltro de partículas, que é uma implementação não paramétrica do ltro Bayesiano. Esse ltro faz a estimação do estado com base nos métodos sequenciais de Monte Carlo e permite trabalhar de uma maneira simples com modelos não lineares. A desvantagem desse tipo de fusão sensorial é o seu alto custo computacional o que geralmente o impede de ser utilizado em aplicações de tempo real. Para que seja possível utilizar esse ltro em tempo real, será proposto neste trabalho uma implementação paralela utilizando uma unidade de processamento gráco (GPU) da NVIDIA e a arquitetura CUDA. Neste trabalho também será feito um estudo da utilização de duas congurações de sensores no sistema de navegação proposto neste trabalho. / The task of navigating a Remotely Operated underwater Vehicles (ROV) during inspection of man-made structures is performed mostly by visual references and occasionally a magnetic compass. Yet, some environments present a combination of low visibility and ferromagnetic anomalies that negates this approach. This paper, motivated by the development of a ROV designed to work on such environment, proposes a navigation method for this kind of vehicle. As the modeling of the system is nonlinear, the method proposed uses a particle lter to represent the vehicle state that is a nonparametric implementation of the Bayes lter. This method to work needs a priori knowledge of the environment map and to make the data association with this map, a 2D image sonar is used. The drawback of the sensor fusion used in this work is its high computational cost which generally prevents it from being used in real time applications. To be possible for this lter to be used in real time application, in this work is proposed a parallel implementation using a graphics processing unit (GPU) from NVIDIA and CUDA architecture. In this work is also made a study of two types of sensors conguration on the navigation system proposed in this work.

For Autonomous Underwater Vehicles (AUVs) to be able to conduct longterm surveys, the ability to return to a docking station for maintenance and recharging is crucial. A dynamic docking system where a slowly moving submarine acts as the docking station provides increased hydrodynamic control and reduces the impact of environmental disturbances. A vision-based relative positioning system using a camera, mounted on the AUV, and light sources, mounted on the docking station, is investigated as a suitable high-resolution and high-frequency solution for a short-range relative positioning system. Detection and identification of the true light sources in the presence of reflections, ambient light, and other luminaries, requires a robust tracking pipeline that can reject false positives. In this thesis, we present a complete tracking pipeline, from image processing to pose estimation, specifically for a soft docking scenario. We highlight the issues of light source detectors based on finding a unique global threshold and detectors based on gradient information and propose a novel method, based on using a suitable threshold for each light source. Rejection of false positives is handled systematically by rejecting pose estimates resulting in large re-projection errors, and a configuration of the light sources is proposed that enhances the pose estimation performance. The performance of the proposed light source detector is evaluated on the D-recovery dataset. Results show that the proposed method outperforms other methods in identifying the light sources. The tracking pipeline is evaluated with experiments as well as a simulation based on the Stonefish simulator. / För att autonoma undervattensfordon ska kunna utföra långsiktiga undersökningar är möjligheten att återvända till en dockningsstation för underhåll och laddning avgörande. Ett dynamiskt dockningssystem där en långsamtgående ubåt agerar som dockningsstation ger en ökad hydrodynamisk kontroll och minskar påverkan av omgivande miljöstörningar. Ett synbaserat, relativt positioneringssystem som använder en kamera, monterad på farkosten, och ljuskällor, monterad på dockningsstationen, undersöks som en lämplig högupplöst och högfrekvent lösning för ett relativt positioneringssystem med kort räckvidd. Detektering och identifiering av de verkliga ljuskällorna i närvaro av reflektioner, omgivande ljus och andra störande ljuskällor kräver ett robust spårningssystem som kan särskilja de sanna ljuskällorna från de omgivande störningarna. I denna uppsats presenteras ett komplett spårningssystem, från bildbehandling till positionsestimering, specifikt för ett soft docking scenario. Vi lyfter fram problem med detektorer baserat på att hitta ett unikt globalt tröskelvärde och detektorer baserade på gradientinformation. Vi föreslår en ny metod baserad på att använda ett lämpligt tröskelvärde för varje ljuskälla. Omgivande störningar hanteras systematiskt genom att avvisa positionestimeringar som resulterar i stora projektionsfel, och en konfiguration av ljuskällorna föreslås som förbättrar positionsestimeringens prestanda. Prestandan hos den föreslagna ljuskällsdetektorn utvärderas på datasetet D-recovery. Resultaten visar att den föreslagna metoden överträffar andra metoder i att identifiera ljuskällorna. Spårningsystemet utvärderas med experiment samt en simulering baserad på Stonefish-simulatorn.

With the rising popularity of ROVs and other UV solutions, more robust and high performance controllers have become a necessity. A model of the ROV or UV can be a valuable tool during control synthesis. The main objective of this thesis was to use a model in design and development of controllers for an ROV. In this thesis, an ROV from Blue Robotics was used. The ROV was equipped with 6 thrusters placed such that the ROV was capable of moving in 6-DOFs. The ROV was further equipped with an IMU, two pressure sensors and a magnetometer. The ROV platform was further developed with EKF-based sensor fusion, a control system and manual control capabilities. To model the ROV, the framework of Fossen (2011) was used. The model was estimated using two different methods, the prediction-error method and an EKF-based method. Using the prediction-error method, it was found that the initial states of the quaternions had a large impact on the estimated parameters and the overall fit to validation data. A Kalman smoother was used to estimate the initial states. To circumvent the problems with the initial quaternions, an \abbrEKF was implemented to estimate the model parameters. The EKF estimator was less sensitive to deviations in the initial states and produced a better result than the prediction-error method. The resulting model was compared to validation data and described the angular velocities well with around 70 % fit. The estimated model was used to implement feedback linearisation which was used in conjunction with an attitude controller and an angular velocity controller. Furthermore, a depth controller was developed and tuned without the use of the model. Performance of the controllers was tested both in real tests and simulations. The angular velocity controller using feedback linearisation achieved good reference tracking. However, the attitude controller could not stabilise the system while using feedback linearisation. Both controllers' performance could be improved further by tuning the controllers' parameters during tests. The fact that the feedback linearisation made the ROV unstable, indicates that the attitude model is not good enough for use in feedback linearisation. To achieve stability, the magnitude of the parameters in the feedback linearisation were scaled down. The assumption that the ROV's center of rotation coincides with the placement of the ROV's center of gravity was presented as a possible source of error. In conclusion, good performance was achieved using the angular velocity controller. The ROV was easier to control with the angular velocity controller engaged compared to controlling it in open loop. More work is needed with the model to get acceptable performance from the attitude controller. Experiments to estimate the center of rotation and the center of gravity of the ROV may be helpful when further improving the model.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In recent years Autonomous Underwater Vehicles (AUVs) have become interesting for harbor mapping and protection. AUVs require a SONAR sensor for observing their surroundings, thus enabling them to perform collision avoidance manoeuvres and scanning their operating environment for intruders or foreign objects, e.g. mines. To perform such actions the SONAR sensor is required to supply very fine range resolution for target imaging, as well as providing information about possible target velocity. Basic SONAR theory is discussed, as well as different approaches to signal design and processing techniques, for achieving the required resolution in range and target velocity. Two of the discussed approaches are selected for processing range and target velocity, respectively. Both approaches are simulated for their validity before being tested by using a custom-built platform. The platform is highly configurable and designed for capacity of testing a variety of SONAR signals and set ups. Furthermore, the platform is built by using off-the-shelf components to minimize development costs. The results of simulations and practical tests are presented. A high correlation between theory and practice is achieved. The knowledge and the platform presented form the stepping stone for further SONAR sensor developments. / AFRIKAANSE OPSOMMING: In die laaste jare het outonome onderwater voertuie (OOV) toenemend belangrik geword vir die kartografie en beskerming van hawens. OOV’s vereis SONAR sensore wat hulle in staat stel, om hulle omgewing waar te neem en sodoende botsing vermydings take te verrig en ook om hul werksomgewing noukeurig te skandeer om indringers of vreemde voorwerpe, bv. myne, op te spoor. Om sulke werk te verrig, word van die SONAR sensor vereis, om baie fyn afstand oplossings vir teiken te verskaf, insluitend die moontlike snelheid van die teiken. Basiese SONAR teorie word bespreek, en dan verskeie benaderings van sein ontwerp en verwerkings tegnieke. Twee van die bespreekte benaderings word gekies om afstand en teiken snelheid onderskeidelik te verwerk. Altwee benaderings word gesimuleer om hul geldigheid vas te stel, voor dat hulle getoets word op ’n pasmaat vervaardigde platform. Die platform is hoogs aanpasbaar en is ontwerp vir sy vermoë om ’n verskeidenheid SONAR seine en verwerkings te hanteer. Verder is die platform vervaardig met standard rakonderdele om ontwikkelingskoste so laag as moontlik te hou. Die uitslae van die simulerings en praktiese toetse word voorgestel. ’n Hoë mate aan korrelasie is bereik tussen teorie en praktyk. Die kennis en die platvorm, wat hier voorgestel word, vorm die eerste trappie vir toekomstige SONAR sensor ontwikkeling.

Approved for public release; distribution is unlimited / Reissued 30 May 2017 with correction to student's affiliation on title page. / Autonomous vehicle teams have great potential in a wide range of maritime sensing applications, including mine countermeasures (MCM). A key enabler for successfully employing autonomous vehicles in MCM missions is motion planning, a collection of algo-rithms for designing trajectories that vehicles must follow. For maximum utility, these algorithms must consider the capabilities and limitations of each team member. At a minimum, they should incorporate dynamic and operational constraints to ensure trajectories are feasible. Another goal is maximizing sensor performance in the presence of uncertainty. Optimal control provides a useful frame-work for solving these types of motion planning problems with dynamic constraints and di_x000B_erent performance objectives, but they usually require numerical solutions. Recent advances in numerical methods have produced a general mathematical and computational framework for numerically solving optimal control problems with parameter uncertainty—generalized optimal control (GenOC)— thus making it possible to numerically solve optimal search problems with multiple searcher, sensor, and target models. In this dissertation, we use the GenOC framework to solve motion planning problems for di_x000B_erentMCMsearch missions conducted by autonomous surface and underwater vehicles. Physics-based sonar detection models are developed for operationally relevant MCM sensors, and the resulting optimal search trajectories improve mine detection performance over conventional lawnmower survey patterns—especially under time or resource constraints. Simulation results highlight the flexibility of this approach for optimal mo-tion planning and pre-mission analysis. Finally, a novel application of this framework is presented to address inverse problems relating search performance to sensor design, team composition, and mission planning for MCM CONOPS development.

Neste trabalho, é abordado o problema da navegação de um veículo submarino autônomo. São propostos estimadores de estado que realizam fusão sensorial baseada em Filtro Estendido de Kalman. Esses estimadores de estado empregam as medidas dos seguintes sensores: uma unidade de medição inercial, um sensor de velocidade por efeito Doppler, um profundímetro e uma bússola. Primeiramente foi projetado um estimador de estados para o AUV Pirajuba, onde a estimação da orientação do veículo é realizada de forma desacoplada à estimação da velocidade e posição do veículo. Em seguida, foram desenvolvidos dois estimadores de estado que estimam orientação, velocidade e profundidade do veículo de forma acoplada. Para o projeto e testes dos estimadores mencionados anteriormente, foi empregada uma base de dados contendo um registro de medições reais dos sensores do veículo submarino autônomo Pirajuba, durante testes de campo no lago de uma represa. Os resultados dos testes validaram os estimadores de estado propostos nesse trabalho. Por último, foi realizada uma análise comparativa dos estimadores de estado mencionados. / This work concerns the navigation problem of an autonomous underwater vehicle. Some state estimators using sensorial fusion were proposed, the sensorial fusion is based in an Extended Kalman Filter. The state estimators are fed by measurements of the following sensors: an inertial measurements unit, a velocity sensor by Doppler effect, a depthmeter and a compass. In the first version of the EKF algorithm, the vehicles attitude estimation was decoupled from the vehicle velocity estimation. The second version considers the coupling between linear velocity and the attitude in the vehicle reference frame, taking the velocity reading for correction of the filter estimates. Finally, in the third version, the coupling between position and attitude is also considered, but the correction of the filters estimates is based on the depth readings. Experiments for supporting the design and validation of the navigation algorithms were based on a database constructed with motion measurements during the AUV maneuvers in the north coast of Sao Paulo, and the Guarapiranga lake in the São Paulo city. This work presents a comparative analysis of those algorithms.

Veículos Submarinos Não Tripulados (UUVs Unmanned Underwater Vehicles) possuem muitas aplicações comerciais, militares e científicas devido ao seu elevado potencial e relação custo-desempenho considerável quando comparados a meios tradicionais utilizados para a obtenção de informações provenientes do meio subaquático. O desenvolvimento de uma plataforma de testes e amostragem confiável para estes veículos requer o projeto de um sistema completo além de exigir diversos e custosos experimentos realizados no mar para que as especificações possam ser devidamente validadas. Modelagem e simulação apresentam medidas de custo efetivo para o desenvolvimento de componentes preliminares do sistema (software e hardware), além de verificação e testes relacionados à execução de missões realizadas por veículos submarinos reduzindo, portanto, a ocorrência de potenciais falhas. Um ambiente de simulação preciso pode auxiliar engenheiros a encontrar erros ocultos contidos no software embarcado do UUV além de favorecer uma maior introspecção dentro da dinâmica e operação do veículo. Este trabalho descreve a implementação do algoritmo de controle de um UUV em ambiente MATLAB/SIMULINK, sua conversão automática para código compilável (em C++) e a verificação de seu funcionamento diretamente no computador embarcado por meio de simulações. Detalham-se os procedimentos necessários para permitir a conversão dos modelos em MATLAB para código C++, integração do software de controle com o sistema operacional de tempo real empregado no computador embarcado (VxWORKS) e a estratégia de simulação com Hardware In The Loop (HIL) desenvolvida - A principal contribuição deste trabalho é apresentar de forma racional uma estrutura de trabalho que facilite a implementação final do software de controle no computador embarcado a partir do modelo desenvolvido em um ambiente amigável para o projetista, como o SIMULINK. / Unmanned Underwater Vehicles (UUVs) have many commercial, military, and scientific applications because of their potential capabilities and significant costperformance improvements over traditional means of obtaining valuable underwater information The development of a reliable sampling and testing platform for these vehicles requires a thorough system design and many costly at-sea trials during which systems specifications can be validated. Modeling and simulation provide a cost-effective measure to carry out preliminary component, system (hardware and software), and mission testing and verification, thereby reducing the number of potential failures in at-sea trials. An accurate simulation environment can help engineers to find hidden errors in the UUV embedded software and gain insights into the UUV operation and dynamics. This work describes the implementation of a UUV\'s control algorithm using MATLAB/SIMULINK, its automatic conversion to an executable code (in C++) and the verification of its performance directly into the embedded computer using simulations. It is detailed the necessary procedure to allow the conversion of the models from MATLAB to C++ code, integration of the control software with the real time operating system used on the embedded computer (VxWORKS) and the developed strategy of Hardware in the loop Simulation (HILS). The Main contribution of this work is to present a rational framework to support the final implementation of the control software on the embedded computer, starting from the model developed on an environment friendly to the control engineers, like SIMULINK.