Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2007. / Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-23T20:52:40Z No. of bitstreams: 1 Projeto e construção de um veículo subaquático não tripulado de baixo custo.pdf: 1267914 bytes, checksum: de003a4ec22d232cb5b78deb87dd39c5 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-08T23:09:06Z (GMT) No. of bitstreams: 1 Projeto e construção de um veículo subaquático não tripulado de baixo custo.pdf: 1267914 bytes, checksum: de003a4ec22d232cb5b78deb87dd39c5 (MD5) / Made available in DSpace on 2013-06-08T23:09:06Z (GMT). No. of bitstreams: 1 Projeto e construção de um veículo subaquático não tripulado de baixo custo.pdf: 1267914 bytes, checksum: de003a4ec22d232cb5b78deb87dd39c5 (MD5) Previous issue date: 2007 / A escassez de alguns recursos naturais como petróleo e gás na superfície terrestre, têm feito com que a raça humana volte sua atenção para as profundezas dos oceanos nestas últimas décadas. Os ROVs (Remotely Operated Vehicle) possuem função importante para o estudo, preservação e execução de tarefas em ambiente subaquático com segurança. Infelizmente no Brasil, as iniciativas de produzir um ROV com tecnologia nacional e de baixo custo, quando comparado a equivalentes importados, são ainda raras e se restringem a algumas poucas instituições acadêmicas, não tendo sido localizado nenhum fabricante comercial deste tipo de veículo no país. Visando preencher esta lacuna, o presente trabalho deu continuidade ao projeto e construção de um ROV de baixo custo iniciado por Moraes em 2005, do qual efetivamente foi aproveitado o projeto estrutural mecânico, que através de pequenas modificações, ganhou uma câmera de vídeo, propulsores mais potentes, e sistema de iluminação. A eletrônica embarcada foi totalmente modificada visando atender às novas exigências de potência do sistema, e de funções antes inexistentes tais como: zoom, foco,nível de iluminação e controle de trajetória efetivado através de um único joystick. O novo modelo de acelerômetro empregado permitiu a medição de aceleração em três eixos ortogonais. Na fase final do trabalho foi incorporado ao ROV um altímetro, o que propiciou alguns resultados experimentais envolvendo controle de profundidade em malha fechada. No último capítulo desta dissertação foram incluídas algumas conclusões e considerações que deverão colaborar para futuras melhorias deste projeto. / The scarcity of some natural resources as oil and gas in the terrestrial surface has called human race attention toward the deepness of the oceans in these last decades. ROVs(Remotely Operated Vehicles) have important function for the study, preservation and execution of tasks in subaqueous environment with security. In Brazil, the initiatives to produce a ROV with national technology and low cost, when compared with imported devices, are still rare and restrict to some academic institutions, not having been found commercial manufacturer of this type of vehicle in the country. Aiming to fill this gap, the present work gave continuity to the project and construction of the ROV of low cost initiated by Moraes in 2005, from which effectively the mechanical structural project was used and, through small modifications, it was incorporaded a video camera, more powerful propellants, and lighting system. The embarked electronics was totally modified aiming to supply the new requirements of power system, and functions before inexistent such as zoom, focus, level of illumination and control of trajectory accomplished through only one joystick. The new model of accelerometer employed allows the measurement of acceleration in three orthogonal axes. In the final phase of the work an altimeter was incorporated to the ROV, which propitiated some experimental results in depth closed loop control. In the last chapter of this dissertation were enclosed some conclusions and considerations that will collaborate for future improvements in this project.

For underwater robotics there exists severe constraints regarding wireless bandwidth in the kilobits range. This makes a centralised approach to high-level mission management possibly less than ideal due to inherent delays and possible temporary incompleteness in data during decision making. This thesis aims to propose, implement (in ROS) and test a distributed approach. An auction based method for task assignment was being used, as well as a Pagerank based approach that models a trust based hierarchy between autonomous agents inferred from information exchange, in order to enforce decision conformity. Simulations where carried out using UWsim and a custom made bandwidth limiter for ROS. It was concluded that the Pagerank based algorithm managed to uphold conformity and solve conflicts during network slowdown but did not always lead to the correct decisions being enforced.

[ES] La robótica submarina ha sido uno de los campos de investigación que más interés ha despertado en las últimas décadas y con esto ha logrado una evolución de dicho campo. Avances de la robótica submarina han sido implementados en áreas diferentes a la investigación, dentro de los beneficiados está el sector comercial y el sector militar, así como la academia. Por otra parte, avances tecnológicos de diferentes áreas se incorporan a la robótica submarina, principalmente en los sistemas electrónicos los que más estimulan el desarrollo de todo lo relacionado con los vehículos submarinos, por lo tanto, se generan progresos en sistemas de control además del diseño mecánico y estructural. Esta tesis se centró en el diseño y construcción de un vehículo autónomo submarino para el proyecto DIVISAMOS. A partir del análisis del estado actual de la robótica submarina, el diseño planteado recoge todos los aspectos favorables de los vehículos existentes, de esta forma se tienen características que optimizan el vehículo, otorgándole versatilidad y eficiencia de funcionamiento. En el proceso investigativo se dirigieron esfuerzos, principalmente a la integración de métodos de diseño mecánico que optimizaron las características del vehículo que se construyó, presentando así un vehículo híbrido con desplazamientos eficientes y con posibilidad de desarrollar misiones que requieran hoovering. Cabe destacar que los métodos de diseño presentados en esta tesis, permiten incorporar sistemas de sensores para desarrollo de misiones de monitoreo, Localización y Mapeo Simultáneos (SLAM, por sus siglas en inglés) batimetría de ambientes submarinos con generación de datos georreferenciados, de alta resolución y su proyección cartográfica. Con todo esto se puede asegurar que se construyó un vehículo de altas prestaciones. Con el análisis de los resultados obtenidos con la implementación de Dinámica de Fluidos Computacional (CFD, por sus siglas en inglés), se logró que el vehículo tenga bajo consumo de energía ya que se han estudiado a fondo aspectos de la forma hidrodinámica del casco, del vehículo para reducir la fuerza de arrastre. Dentro de los resultados a desatacar en este aspecto se presenta un modelo que incorpora el cálculo en tiempo real, de las fuerzas debidas al arrastre generado por las corrientes de agua que interactúan con el casco del vehículo, reduciendo con esto el alto costo computacional de los análisis CFD y enriqueciendo el modelado dinámico. El modelo dinámico y cinemático de un vehículo autónomo submarino (AUV, por sus siglas en inglés), reviste un mayor grado de complejidad debido a que al sumergirse, depende de la navegación inercial que funciona basada en las mediciones de los instrumentos y los sistemas de referencia para determinar su posición. Las matrices de transformación son un método eficaz, usado para el modelado matemático de brazos robot, en esta tesis se plateó un modelo matemático hibrido, que utiliza matrices de transformación para plantear la cinemática del AUV, éste modelo tiene la particularidad de permitir agregar elementos al modelo inicial, continuando con la misma formulación resultando de gran utilidad para casos en los que el AUV realiza misiones en las que manipulan objetos y debido a esto se incorpora un brazo robot. / [CA] La robòtica submarina ha sigut un dels camps d'investigació que més interés ha despertat en les últimes dècades, açò ha aconseguit una evolució del dit camp. Avanços de la robòtica submarina han sigut implementats en àrees diferents de la investigació, dins dels beneficiats està el sector comercial i el sector militar així com l'acadèmia. D'altra banda, avanços tecnològics de diferents àrees s'incorporen a la robòtica submarina, principalment són els sistemes electrònics els que més estimulen el desenrotllament de tot allò que s'ha relacionat amb els vehicles submarins, per tant es generen progressos en sistemes de control a més del disseny mecànic i estructural. Esta tesi es va centrar en el disseny i construcció d'un vehicle autònom submarí per al projecte DIVISAMOS. A partir de l'anàlisi de l'estat actual de la robòtica submarina, el disseny plantejat arreplega tots els aspectes favorables dels vehicles existents, d'esta manera es tenen característiques que optimitzen el vehicle atorgant-li versatilitat i eficiència de funcionament. En el procés investigativo es van dirigir esforços principalment a la integració de mètodes de disseny mecànic que van optimitzar les característiques del vehicle que es va construir, presentant així un vehicle híbrid amb desplaçaments eficients i possibilitat de desenrotllar missions que requerisquen hoovering. Cal destacar que els mètodes de disseny presentats en esta tesi permeten incorporar sistemes de sensors per a desenrotllament de missions de monitoreo, SLAM, batimetria d'ambients submarins amb generació de dades geo-referenciats d'alta resolució i la seua projecció cartogràfica. Amb tot açò es pot assegurar que es va construir un vehicle d'altes prestacions. Amb l'anàlisi dels resultats obtinguts amb la implementació de Dinàmica de Fluids Computacional (CFD, per les seues sigles en anglés) es va aconseguir que el vehicle tinga baix consum d'energia ja que s'han estudiat a fons aspectes de la forma hidrodinàmica del casc del vehicle per a reduir la força d'arrossegament. Dins dels resultats a descordar en este aspecte es presenta un model que incorpora el càlcul en temps real de les forces degudes a l'arrossegament generat pels corrents d'aigua que interactuen amb el casc del vehicle, reduint amb açò l'alt cost computacional de les anàlisis CFD i enriquint el modelatge dinàmic El model dinàmic i cinemático d'un Vehicle Autònom Submarí (AUV, per les seues sigles en anglés) revist un major grau de complexitat pel fet que al submergir-se depén de la navegació inercial que funciona basada en els mesuraments dels instruments i els sistemes de referència per a determinar la seua posició. Les matrius de transformació són un mètode eficaç usat per al modelatge matemàtic de braços robot, en esta tesi es va platejar un model matemàtic híbrid que utilitza matrius de transformació per a plantejar la cinemàtica del' AUV, este model té la particularitat de permetre agregar elements al model inicial continuant amb la mateixa formulació, resultant gran utilitat per a casos en què l'AUV realitza missions en què manipulen objectes i a causa d'açò incorpora un braç robot. / [EN] Underwater robotics has been one of the fields of research that has awakened most in recent decades, this has achieved an evolution of this field. Advances in underwater robotics have been implemented in areas other than research, within the benefits are the commercial sector and the military sector as well as the academy. Underwater robotics has been one of the fields of research that has awakened most in recent decades, this has achieved an evolution of this field. Advances in underwater robotics have been implemented in areas other than research, within the benefits is the commercial sector and the military sector as well as the academy. The development of everything related to underwater vehicles, therefore progress is made in control systems in addition to the mechanical and structural design. This thesis focused on the design and construction of an underwater autonomous vehicle for the DIVISAMOS project. From the analysis of the current state of underwater robotics, the proposed design includes all the favorable aspects of the existing vehicles, in this way it has characteristics that optimize the vehicle, giving it versatility and efficiency of operation. In the research process, it was mainly aimed at the integration of mechanical design methods that optimize the characteristics of the vehicle that was built, thus presenting a hybrid truck with efficient displacements and the possibility of development. It should be noted that the design methods presented in this test incorporate sensor systems for the development of monitoring missions, Simultaneous Localization and Mapping (SLAM), the bathymetry of submarine environments with high-resolution georeferenced data generation and its cartographic projection. With all this you can ensure that a high-performance vehicle was built. With the analysis of the results obtained with the implementation of Computational Fluid Dynamics (CFD) was achieved that the vehicle has low power consumption and that has been thoroughly studied aspects of the hydrodynamic shape of the vehicle's hull to reduce the drag force. Within the results of this aspect a model is presented that incorporates the calculation in real time of the forces for the analysis of the drag generated by the water currents that interact with the hull of the vehicle, reducing with this the high computational cost of the CFD analysis and enriching dynamic modeling. The dynamic and kinematic model of an Autonomous Underwater Vehicle (AUV) revises a greater degree of complexity that depends on the inertial navigation that works in the measurements of the instruments and the reference to determine its position. Transformation matrices are an effective method used for the mathematical modeling of robot arms. In this thesis a hybrid mathematical model was used that uses transformation matrices to propose the kinematics of the AUV, this model has the peculiarity of allowing the aggregation of elements to the initial model continuing with the same formulation, resulting in a great utility for cases in which the AUV performs missions in which objects are manipulated and due to this incorporates an arm robot. / También agradezco al ministerio de educación pues gracias a los recursos destinados al proyecto DIVISAMOS todo este proyecto fue posible. / Aguirre Gómez, FA. (2020). Diseño Optimizado, Modelado Dinámico - Cinemático y Fabricación de un AUV, Integrando Herramientas CAE para su Validación [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/144260 / TESIS

The work in this thesis is concerned with the generation of Lumped Parameter Models (LPM) for two, slender, torpedo shaped, X-fin craft. This process involves the use of CFD to simulate captive maneuvers that are normally performed using test equipment in the field. These captive maneuvers are refereed to as planar motion mechanisms (PMM), and when simulated through CFD are refereed to as virtual planar motion mechanisms (VPMM). The results from VPMM are used to determine the hydrodynamic derivatives that inform the LPM. There was some inconsistency in the VPMM data based on the frequency and amplitude that the VPMM was run. A brief study was run to look at this effect. Afterwards, Open and closed loop, autopilot assisted, maneuvers are implemented and performed using the LPM model through Simulink. Results of these maneuvers are analyzed for craft stability. Additionally, comparisons of LPM maneuvers to field data are performed. Critiques of the craft stability and effect of the autopilot are made. / Master of Science / The work carried out in this thesis involves the creation of a physics based model of an underwater craft. This physics based model is informed through characteristics determined by running computational fluid dynamics (CFD) simulations. The benefit of such a model, is the simplification from CFD to a 6 degree of freedom (6-DOF) lumped parameter model (LPM). These physics models, LPM, are generated for two particular craft of interest. One craft is an existing design used by NUWC (named Tonnetto), while the other design is one generated to be similar in shape and size to the NUWC craft (named Hokie). Computer simulated maneuvers are carried out using these models to asses craft stability and performance. An autopilot is implemented into the models for some of these simulations to see its affects on the crafts performance. Additionally, these simulated maneuvers are compared to field data collected by NUWC.

This thesis examines two methods for monocular visual odometry, FAST + KLT and ORBSLAM2, in the case of underwater environments.This is done by implementing and testing the methods on different underwater datasets. The results for the FAST + KLT provide no evidence that this method is effective in underwater settings. However, results for the ORBSLAM2 indicate that good performance is possible whenproperly tuned and provided with good camera calibration. Still, thereremain challenges related to, for example, sand bottom environments and scale estimation in monocular setups. The conclusion is therefore that the ORBSLAM2 is the most promising method of the two tested for underwater monocular visual odometry. / Denna uppsats undersöker två metoder för monokulär visuell odometri, FAST + KLT och ORBSLAM2, i det särskilda fallet av miljöer under vatten. Detta görs genom att implementera och testa metoderna på olika undervattensdataset. Resultaten för FAST + KLT ger inget stöd för att metoden skulle vara effektiv i undervattensmiljöer. Resultaten för ORBSLAM2, däremot, indikerar att denna metod kan prestera bra om den justeras på rätt sätt och får bra kamerakalibrering. Samtidigt återstår dock utmaningar relaterade till exempelvis miljöer med sandbottnar och uppskattning av skala i monokulära setups. Slutsatsen är därför att ORBSLAM2 är den mest lovande metoden av de två testade för monokulär visuell odometri under vatten.

This thesis presents the integration of an acoustic tracking system within an autonomous underwater AUV (AUV) to enable real-time tracking of sharks tagged with artificial acoustic sources. The tracking system consists of two hydrophones and a receiver unit that outputs a measurement of the relative angle to the tagged shark. Since only two hydrophones are used, the sign of the relative angle measurement is unknown. To overcome this ambiguity, a particle filter algorithm was developed to estimate the position of the acoustic source. When combined with an active control system that drives vehicle to obtain different orientations with respect to the acoustic source, real-time autonomous localization, tracking, and following of a tagged shark is shown to be possible. Four types of ocean experiments were used to validate the system including: 1) AUV tracking of a stationary tag, 2) AUV tracking of a tagged kayak, 3) AUV tracking of a tagged AUV, and 4) AUV tracking of a tagged shark. These experiments were analyzed with respect to the localization error, associated error variance, and distance between the AUV and the tag. The final shark tracking experiments took place in SeaPlane Lagoon, Los Angeles, CA, where the AUV was able to autonomously track and follow a tagged Leopard Shark for several hours.

This thesis proposes a method to simulate the dynamics of an autonomous underwater vehicle towing another autonomous underwater vehicle of equivalent size using a marine cable in the vertical and horizontal plane. There is a coupling effect between the two vehicles because the towed vehicle is of equivalent size. This means that the towed vehicle cannot be modeled as just a payload but rather, must incorporate the forces and moments experienced and acting on it. In this work, only AUVs with symmetrical hulls are considered, where the towing AUV is moving at a constant velocity with a set thrust while the towed AUV has no thrust. The rope system is another important component that needs to be modeled correctly because the rope material and type significantly impact the motion of the vehicles. The rope system in this study is modeled using a numerical approach called the lumped mass spring damper method which is easy to understand and computationally inexpensive. The rope model accounts for buoyancy differences in different ropes and permits cable flexibility. This thesis enables us to study the motion of multiple combinations of different ropes and axi-symmetric types of underwater vehicles with any fixed or movable fin configuration. / M.S. / This thesis studies the motion of an autonomous underwater vehicle towing another autonomous underwater vehicle which is a large as it is. The towed vehicle cannot be assumed to be just a mass attached to the towing vehicle. There is an interaction between the two vehicle. The towed vehicle places a force on the towed vehicle and the towed vehicle likewise places a force on the towing vehicle. This interaction needs to be modeled correctly to fully capture the impact of both vehicles and their appendages. Additionally, the rope system poses a huge impact on the two vehicle depending on what type of rope is selected. Multiple factors affect the performance of a rope such as the shape and the elasticity. Some ropes may also be denser due to their material type and are less buoyant than others. These factors are considered in the modeling of the overall system and allows us to study different combinations of ropes and symmetric hulled autonomous underwater vehicles.

Recent developments in autonomous underwater vehicles (AUV) have created the need for a low cost AUV that is comparable in class and payload capabilities to existing, commercially available, expensive and sub-optimal crafts. The Navy is active in research of autonomous, unmanned, highly efficient, high speed underwater craft. Small, low cost AUVs capable of swarm control are of special interest for military mine applications. No matter the nature of the application or class of craft, a common challenge is the accuracy of maneuvering predic- tions. Maneuvering predictions not only affect design, but also the real time understanding of mission capabilities and endurance. Thus the proliferation of AUVs in recent times for commercial and defense applications have led to the need of higher fidelity of physics based lumped parameter models. The sensor data, along with maneuvering model data can tie into a more accurate trajectory. Multiple such incremental advances in the literature for prediction of maneuvering shall lead to a more accuracy. This work hopes to bridge some important gaps that ensure the creation of such a non-linear LPM to predict the maneuver- ing characteristics of an AUV using non linear hydrodynamic derivatives obtained through static and dynamic CFD. This model shall be implemented for the craft designed for DIVE technologies, our industrial sponsor and an in-house craft, the 690. This model shall also be made generalized for most submerged craft with a torpedo or slender hull form, with cruciform or X configuration of fins. This dissertation looks to provide the framework to identify CFD informed high fidelity dynamic model for AUVs. The model thus created shall be spe- cialized to account for specific important effects such as flow interaction among appendages, effect of using steady and unsteady maneuvers as CFD information and kinematic charac- teristics of captive maneuvers. The specific, innovative contributions in this dissertation are listed below: 1. Definition of a new stability index to incorporate effects of gravity at low-moderate speeds 2. Novel method for identification of hydrodynamic derivatives 3. Systematic and comprehensive study on the parameters affecting VPMM / Doctor of Philosophy / The maneuvering model for an AUV is an indispensable tool that makes the autonomy part of AUVs possible and efficient. The maneuvering model that exists today is mostly linearized and of lower fidelity to increase efficiency. The use of a non linear, higher order hydrodynamic model facilitates better accuracy of maneuvering predictions, essential to mission completion of AUVs applied in research and defense sectors. This higher fidelity can be achieved through informing the model using CFD that is reasonably efficient in computation. This dissertation presents a non-linear, higher order hydrodynamic maneuvering model for the 690 and DIVE crafts, informed with steady and unsteady CFD.

This thesis presents the design and development of a novel biomimetic jellyfish robot that features ionic polymer metal composite actuators. The shape and swimming style of this underwater vehicle are based on oblate jellyfish species, which are known for their high locomotive efficiency. Ionic polymer metal composites (IPMC) are used as actuators in order to contract the bell and thus propel the jellyfish robot. This research focuses on translating the evolutionary successes of the natural species into a jellyfish robot that mimics the geometry, the swimming style, and the bell deformation cycle of the natural species. Key advantages of using IPMC actuators over other forms of smart material include their ability to exhibit high strain response due to a low voltage input and their ability to act as artificial muscles in water environment. This research specifically seeks to implement IPMC actuators in a biomimetic design and overcome two main limitations of these actuators: slow response rate and the material low blocking force. The approach presented in this document is based on a combination of two main methods, first by optimizing the performance of the IPMC actuators and second by optimizing the design to fit the properties of the actuators by studying various oblate species. Ionic polymer metal composites consist of a semi-permeable membrane bounded by two conductive, high surface area electrode. The IPMCs are manufactured is several variations using the Direct Assembly Process (DAP), where the electrode architecture is controlled to optimize the strain and stiffness of the actuators. The resulting optimized actuators demonstrate peak to peak strains of 0.8 % in air and 0.7 % in water across a frequency range of 0.1-1.0 Hz and voltage amplitude of 2 V. A study of different oblate species is conducted in order to attain a model system that best fits the properties of the IPMC actuators. The Aequorea victoria is chosen based on its bell morphology and kinematic properties that match the mechanical properties of the IPMC actuators. This medusa is characterized by it low swimming frequency, small bell deformation during the contraction phase, and high Froude efficiency. The bell morphology and kinematics of the Aequorea victoria are studied through the computation of the radius of curvature and thus the strain energy stored in the during the contraction phase. The results demonstrate that the Aequorea victoria stores lower strain energy compared to the other candidate species during the contraction phase. Three consecutive jellyfish robots have been built for this research project. The first generation served as a proof of concept and swam vertically at a speed of 2.2 mm/s and consumed 3.2 W of power. The second generation mimicked the geometry and swimming style of the Aurelia aurita. By tailoring the applied voltage waveform and the flexibility of the bell, the robot swam at an average speed of 1.5 mm/s and consumed 3.5 W of power. The third and final generation mimicked the morphology, swimming behavior, and bell kinematics of the Aequorea victoria. The resulting robot, swam at an average speed of 0.77 mm/s and consumed 0.7 W of power when four actuators are used while it achieved 1.5 mm/s and 1.1 W of power consumption when eight actuators are used. Key parameter including the type of the waveform, the geometry of the bell, and position and size of the IPMC actuators are identified. These parameters can be hit later in order to further optimize the design of an IPMC based jellyfish robot. / Master of Science

Rapporten avhandlar en konceptstudie för omvandling av termisk energi till elektrisk samt mekanisk energi, i den autonoma undervattensfarkosten SAPPHIRES. Inledningsvis utreds vilka förväntningar och krav som finns på konceptet för energiomvandling samt om där finns någon publicerad litteratur som redan gjort ansträngningar för att lösa det aktuella problemet. Allmän teori kring värmemotorer och en bred, systematisk litteratursökning inkluderas även i det arbetet. Energiomvandlingen antas kunna ske enligt två fall kallade ”hög-prestanda” och ”låg/medel-prestanda”, vilka innebär att mekanisk samt elektrisk effekt, respektive endast elektrisk effekt ska kunna levereras av konceptet. De mekaniska samt elektriska effekterna ska, vidare, kunna levereras om maximalt 600, respektive 6 kW, och konceptet ska åtminstone kunna uppfylla ett av energiomvandlingsfallen. Den faktiska konceptstudien utgörs av två iterationer av konceptgenereringar, -utvärderingar och -val och de visar att ett koncept kallat ”Öppet system inspirerat av nukleär värmeframdrivning” förefaller vara det bästa sättet att omvandla termisk energi i SAPPHIRES. Därtill indikerar en mer detaljerad analys, bestående av bland annat matematisk modellering och konceptuell konstruktion, att konceptet möjligen skulle kunna uppfylla så kallad ”hög-prestanda” och sedermera leverera både mekanisk och elektrisk effekt om 600, respektive 6 kW. Mer specifikt visar en matematisk analys, med hjälp av vissa antaganden rörande konceptets funktion, att ett ”Öppet system inspirerat av nukleär värmeframdrivning” skulle kunna leverera en mekanisk effekt om 1025 kW samt en elektrisk effekt om 141 kW. En grov, konceptuell konstruktion bekräftar också att konceptets vitala, ingående komponenter faktiskt kan rymmas inom de specificerade dimensionskraven (en cylinderformad volym med en längd och diameter om 1,7, respektive 0,5 m.). Det står dock klart att de möjliga koncepten för energiomvandling kraftigt begränsas av deras möjligheter att leverera tillräcklig mekanisk effekt, för att uppnå ”hög-prestanda”. Om endast ”låg/medel-prestanda” ska uppfyllas tillåts fler av de möjliga koncepten och i ett sådant fall skulle faktorer som underhåll, miljöpåverkan och SAPPHIRES signatur kunna prioriteras i högre utsträckning. / The report discusses a concept study regarding the conversion of thermal energy into electrical and mechanical energy, in the autonomous underwater vehicle SAPPHIRES. First, the requirements and expectations regarding the concept of energy conversion are investigated and efforts are made to identify any published literature, which has already made attempts of solving the issue. General theory regarding heat engines and an extensive literature study are also included in this work. The energy conversion is assumed to perform according to two cases called "high-performance" and "low/medium-performance", meaning mechanical and electrical energy or electrical power should be delivered by the concept, respectively. More specifically, the mechanical and electrical powers should be delivered of a maximum of 600 and 6 kW, respectively and the concept should at least fulfill one of the performance settings. The actual concept study comprises of two iterations of concept generations, evaluations and selections and shows that a concept called "Open system inspired by nuclear thermal propulsion" seems to be the best way of converting thermal energy on-board SAPPHIRES. Moreover, a more detailed analysis, comprising of, inter alia, mathematical modelling and conceptual design, indicates that the concept possibly can meet the so-called "high-performance" and thus, deliver both mechanical and electrical powers of 600 and 6 kW, respectively. More specifically, a mathematical analysis, based on some assumptions regarding the concept's functionality, shows that an "Open system inspired by nuclear thermal propulsion" could deliver a mechanical power of 1025 kW and an electrical power of 141 kW. Rough conceptual design also shows that the vital parts of the concept could fit within the specified maximal dimensions (a cylinder-shaped volume with a length and diameter of 1.7 and 0.5 m, respectively). However, it is clear the possible concepts of energy conversion are severely limited by their capacities of delivering enough mechanical energy, to meet the "high-performance" demands. Assuming only the "low/medium-performance" has to be met, more possible concepts becomes available and in that case, factors such as maintenance, environmental impact and signature of SAPPHIRES could be considered to a greater extent.