Design, Modeling, and Simulation of a Wing Sail Land Yacht

Autonomous land yachts can play a major role in the context of environmental monitoring, namely, in open, flat, windy regions, such as iced planes or sandy shorelines. This work addresses the design, modeling, and simulation of a land yacht probe equipped with a rigid free-rotating wing sail and tail flap. The wing was designed with a symmetrical airfoil and dimensions to provide the necessary thrust to displace the vehicle. Specifically, it proposes a novel design and simulation method for free rotating wing sail autonomous land yachts. The simulation relies on the Gazebo simulator together with the Robotic Operating System (ROS) middleware. It uses a modified Gazebo aerodynamics plugin to generate the lift and drag forces and the yawing moment, two newly created plugins, one to act as a wind sensor and the other to set the wing flap angular position, and the 3D model of the land yacht created with Fusion 360. The wing sail aligns automatically to the wind direction and can be set to any given angle of attack, stabilizing after a few seconds. Finally, the obtained polar diagram characterizes the expected sailing performance of the land yacht. The described method can be adopted to evaluate different wing sail configurations, as well as control techniques, for autonomous land yachts.This work was partially financed by National Funds through the FCT – Fundação para a Ciência e a 337 Tecnologia (Portuguese Foundation for Science and Technology) as part of project UIDB/50014/2020.info:eu-repo/semantics/publishedVersio

Modelling and Simulation of a Wing Sail Land Yacht

A maioria dos veículos autónomos utilizam baterias elétricas ou combustível como fonte de propulsão e alimentação. Contudo, estas fontes energéticas são dispendiosas, poluentes e não sustentáveis. O vento constitui uma fonte propulsora natural, gratuita e sustentável, o que pode, em certas situações, substituir motores eléctricos e de explosão. O objetivo desta dissertação é desenhar uma vela de asa rígida, de rotação livre, e integrá-la num veículo terrestre autónomo com um sistema de controlo baseado em Robot Operating System (ROS). O estudo inicial deste trabalho abrangeu: (i) veleiros terrestres tripulados e não tripulados e as suas respetivas competições; (ii) perfis alares do National Advisory Committee for Aeronautics (NACA); e (iii) diferentes tipos de materiais e componentes eletrónicos usados em veleiros terrestres autónomos. De seguida, desenhou-se uma plataforma composta por um chassis de quatro rodas, uma vela asa com cauda (ambas com um perfil alar NACA63(3)-018), um sistema de controlo de cauda (que usa o ˆangulo de ataque atual e desejado como entradas), e um sistema de controlo da direção (que usa a posição atual e desejada como entradas). Na etapa seguinte, procedeu-se à simulação da plataforma desenhada no ambiente de simulação Gazebo. Para isso, foi criado um modelo do veleiro terrestre, usando o software de Computer-Aided Design (CAD) Fusion 360, e foi importado para o Gazebo. Posteriormente, foram adicionados vários plugins ao ambiente de simulação, nomeadamente plugins importados, alterados e desenvolvidos de raiz. O sistema de controlo foi desenvolvido em ambiente ROS, usando um controlador Proportional - Differential (PD) para a cauda da asa e um controlador Proportional (P) para a direção da plataforma. Finalmente, foram realizados testes de controlo da vela asa, para validar o controlo via cauda e a propulsão do veículo, e testes de controlo da direção, para validar o mecanismo de direção e a capacidade de seguimento de rotas. Os resultados demonstram o correto funcionamento dos sistemas de simulação e controlo.The majority of autonomous vehicles use electric batteries or fossil fuels for propulsion and power. However, these energy sources are costly, pollutant and unsustainable. The wind is a natural, free and sustainable propellant and energy source and can, in certain situations, replace electric and combustion engines. The objective of this dissertation is to design a free rotating rigid wing sail and integrate it in an autonomous land vehicle with a control system based on Robot Operating System (ROS). The initial study of this work covered: (i) manned and unmanned land yachts as well as the respective competitions; (ii) National Advisory Committee for Aeronautics (NACA) airfoils; and (iii) different types of materials and electronic components used in autonomous land yachts. Subsequently, a land yacht platform, consisting of a four-wheeled chassis, a wing sail with a flap tail (both with NACA63(3)-018 airfoils), a flap control system (that uses the current and desired angle of attack as inputs), and a steering control system (which uses the current and desired position as inputs), was designed. Then, the designed platform was simulated in the Gazebo simulation environment. For this, the land yacht model was created, using the Fusion 360 CAD software, and imported into Gazebo. Next, several plugins were added to the simulation environment, ranging from imported to changed and newly developed plugins. The control system was developed in ROS, using a Proportional - Differential (PD) controller for the wing flap and a Proportional (P) controller for the platform direction. Finally, wing control tests were carried out to validate the flap control and vehicle propulsion, and steering control tests to validate the steering mechanism and the ability to follow routes. The results demonstrate the correct functioning of the simulation and control systems

Advanced Techniques for Design and Manufacturing in Marine Engineering

Modern engineering design processes are driven by the extensive use of numerical simulations; naval architecture and ocean engineering are no exception. Computational power has been improved over the last few decades; therefore, the integration of different tools such as CAD, FEM, CFD, and CAM has enabled complex modeling and manufacturing problems to be solved in a more feasible way. Classical naval design methodology can take advantage of this integration, giving rise to more robust designs in terms of shape, structural and hydrodynamic performances, and the manufacturing process.This Special Issue invites researchers and engineers from both academia and the industry to publish the latest progress in design and manufacturing techniques in marine engineering and to debate the current issues and future perspectives in this research area. Suitable topics for this issue include, but are not limited to, the following:CAD-based approaches for designing the hull and appendages of sailing and engine-powered boats and comparisons with traditional techniques;Finite element method applications to predict the structural performance of the whole boat or of a portion of it, with particular attention to the modeling of the material used;Embedded measurement systems for structural health monitoring;Determination of hydrodynamic efficiency using experimental, numerical, or semi-empiric methods for displacement and planning hulls;Topology optimization techniques to overcome traditional scantling criteria based on international standards;Applications of additive manufacturing to derive innovative shapes for internal reinforcements or sandwich hull structures

Design, operation and analysis of wind-assisted cargo ships

This study presents a novel approach to analytically capture aero- and hydrodynamic interaction effects on wind-assisted ships. Low aspect ratio wing theory is applied and modified to be used for the prediction of lift and drag forces of hulls sailing at drift angles. Aerodynamic interaction effects are captured by analytically solving the Navier-Stokes equation for incompressible, potential flow. The developed methods are implemented to a 4 degrees-of-freedom performance prediction model called “ShipCLEAN”, including a newly developed method for rpm control of Flettner rotors on a ship to maximize fuel savings. The accuracy of the model is proven by model- and full-scale verification. To present the variability of the model, two case study ships, a tanker and a RoRo, are equipped with a\ua0total of 11 different arrangements of Flettner rotors. The fuel savings and payback times are assessed using realistic weather from ships traveling on a Pacific Ocean route (tanker) and Baltic Sea route (RoRo). The results verify the importance of using a 4 degrees-of-freedom ship performance model, aero- and hydrodynamic interaction and the importance of controlling the rpm of each rotor individually. Fuel savings of 30% are achieved for the tanker,\ua0and 14% are achieved for the RoRo

Concept design of a fast sail assisted feeder container ship

A fast sail assisted feeder container ship concept has been developed for the 2020 container market in the South East Asian and Caribbean regions.The design presented has met the requirements of an initial economic study, with a cargo capacity of 1270 twenty-foot equivalent unit containers, meeting the predictions of container throughput derived from historical data. In determining suitable vessel dimensions, account has also been taken for port and berthing restrictions, and considering hydrodynamic performance. The vessel has been designed for a maximum speed of 25 knots, allowing it to meet the demand for trade whilst reducing the number of ships operating on the routes considered.The design development of the fast feeder concept has involved rigorous analyses in a number of areas to improve the robustness of the final design. Model testing has been key to the development of the concept, by increasing confidence in the final result. This is due to the fact that other analysis techniques are not always appropriate or accurate. Two hull forms have been developed to meet requirements whilst utilising different propulsor combinations. This has enabled evaluation of efficiency gains resulting from different hydrodynamic phenomena for each design. This includes an evaluation of the hydrodynamic performance when utilising the sail system. This has been done using a combination of model test results and data from regression analysis. The final propulsor chosen is a contra-rotating podded drive arrangement. Wind tunnel testing has been used to maximise the performance of a Multi-wing sail system by investigating the effects of wing spacing, stagger and sail-container interactions. This has led to an increase in lift coefficient of 32% from initial predictions. The savings in power requirement due to the sail system are lower than initially predicted. However, another benefit of their installation, motion damping, has been identified. Whilst this has not been fully investigated, additional fuel savings are possible as well as improved seakeeping performance.The design is shown to be environmentally sustainable when compared to existing vessels operating on the proposed routes. This is largely due to the use of low-carbon and zero-sulphur fuel (liquefied natural gas) and improvements in efficiency regarding operation. This especially relates to cargo handling and scheduling. Green house gas emissions have been predicted to fall by 42% and 40% in the two regions should the design be adopted. These savings are also due to the use of the Multi-wing sail system, which contributes to reductions in power requirement of up to 6% when the vessel operates at its lower speed of 15 knots. It is demonstrated that the fast feeder is also economically feasible, with predicted daily cost savings of 27% and 33% in the South East Asian and Caribbean regions respectively. Thus the fast feeder container ship concept is a viable solution for the future of container transhipment. <br/

Autonomous Sailboat Navigation

The purpose of this study was to investigate novel methods on an unmanned sailing boat, which enables it to sail fully autonomously, navigate safely, and perform long-term missions. The author used robotic sailing boat prototypes for field experiments as his main research method. Two robotic sailing boats have been developed especially for this purpose. A compact software model of a sailing boat's behaviour allowed for further evaluation of routing and obstacle avoidance methods in a computer simulation. The results of real-world experiments and computer simulations are validated against each other. It has been demonstrated that autonomous boat sailing is possible by the effective combination of appropriate new and novel techniques that will allow autonomous sailing boats to create appropriate routes, to react properly on obstacles and to carry out sailing manoeuvres by controlling rudder and sails. Novel methods for weather routing, collision avoidance, and autonomous manoeuvre execution have been proposed and successfully demonstrated. The combination of these techniques in a layered hybrid subsumption architecture make robotic sailing boats a promising tool for many applications, especially in ocean observation

Dynamic yacht strategy optimisation

Yacht races are won by good sailors racing fast boats. A good skipper takes decisions at key moments of the race based on the anticipated wind behaviour and on his position on the racing area and with respect to the competitors. His aim is generally to complete the race before all his opponents, or, when this is not possible, to perform better than some of them. In the past two decades some methods have been proposed to compute optimal strategies for a yacht race. Those strategies are aimed at minimizing the expected time needed to complete the race and are based on the assumption that the faster a yacht, the higher the number of races that it will win (and opponents that it will defeat). In a match race, however, only two yachts are competing. A skipper’s aim is therefore to complete the race before his opponent rather than completing the race in the shortest possible time. This means that being on average faster may not necessarily mean winning the majority of races. This thesis sets out to investigate the possibility of computing a sailing strategy for a match race that can defeat an opponent who is following a fixed strategy that minimises the expected time of completion of the race. The proposed method includes two novel aspects in the strategy computation: A short-term wind forecast, based on an Artificial Neural Network (ANN) model, is performed in real time during the race using the wind measurements collected on board. Depending on the relative position with respect to the opponent, decisions with different levels of risk aversion are computed. The risk attitude is modeled using Coherent Risk Measures. The proposed algorithm is implemented in a computer program and is tested by simulating match races between identical boats following progressively refined strategies. Results presented in this thesis show how the intuitive idea of taking more risk when losing and having a conservative attitude when winning is confirmed in the risk model used. The performance of ANN for short-term wind forecasting is tested both on wind speed and wind direction. It is shown that for time steps of the order of seconds and adequate computational power ANN perform better than linear models (persistence models, ARMA) and other nonlinear models (Support Vector Machines). The outcome of the simulated races confirms that maximising the probability of winning a match race does not necessarily correspond to minimising the expected time needed to complete the race

Um modelo computacional de criatividade

Tese de doutoramento em Engenharia Informática (Inteligência Artificial) apresentada à Fac. de Ciências e Tecnologia de CoimbraThe main motivation of this thesis is the appealing, yet often controversial, goal of computational modelling of creativity. A cross-disciplinary study of the subject of creativity is the mandatory first step and the synthesis towards an AI perspective its intended consequence. From this perspective, we focus on a Model of Concept Invention and, more practically, on a computational system, Divago. The Model of Concept Invention is built over the expected principles for a creative system. It is formalized, although in a computationally idealistic manner, i.e. its implied complexity prevents it from a feasible implementation. Divago is the partial instantiation of this abstract model and comprises the main technical substance of the thesis. Among other aspects, it includes an implementation of the cognitive linguistics framework of Conceptual Blending, as well as a mapping algorithm based on Metaphor work. Divago was subject to experimentation in a range of applications and analyzed according to methodologies that have been proposed with the area of Creativity and AI. Other validation procedures are followed, namely in the comparison to other works and to Conceptual Blending literature.A principal motivação desta tese é o promissor, apesar de muitas vezes controverso, objectivo da modelização computacional de criatividade. Um estudo multi-disciplinar sobre o tema da criatividade é o primeiro passo fundamental e a síntese conducente a uma perspectiva da Inteligência Artificial (IA) sua esperada consequência. Desta perspectiva, focamos um Modelo de Invenção de Conceitos e, de um ponto de vista mais prático, num sistema computacional, o Divago. O Modelo de Invenção de Conceitos é construído sobre um conjunto de princípios identificados como participantes num sistema criativo. É formalizado, embora num perspectiva idealista em termos da sua realização computacional, i.e. a sua complexidade impede, à partida, a consideração de uma directa implementação. O sistema Divago é então a instanciação parcial deste modelo abstracto e compreende as principais contribuições técnicas desta tese. De entre outros aspectos, inclui uma implementação computacional da Integração Conceptual (Conceptual Blending), estudada correntemente na área da Linguística Cognitiva, e também um algoritmo baseado em trabalho sobre metáfora. O Divago foi testado face a um conjunto de aplicações e analisado de acordo com metodologias que têm sido propostas no contexto da Criatividade e IA. Outros procedimentos de validação foram seguidos, nomeadamente a comparação com outros trabalhos e confrontação com os casos propostos na literatura sobre Integração Conceptual

New Advances in Marine Engineering Geology

The ocean is the cradle of life and is rich in natural resources. With the worldwide boom in exploration and application of ocean resources, a dramatically increasing amount of coastal engineering and offshore engineering facilities have been constructed in the last few decades. The rapid development of human economic activities and the global climate change have significant impacts on the marine environment, resulting in frequent geological disasters. Under this circumstance, there is an urgent demand for a platform for scientists and engineers to share their state-of-art research outcomes in the field of Marine Engineering Geology. This book is a collection of a series of articles from the 2nd International Symposium of Marine Engineering Geology (ISMEG 2019), presenting some of the recent efforts made towards marine engineering geology and geotechnics, including theoretical advances, laboratory and field testing, design methods, and the potential for further development of these disciplines