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

From Rousettus aegyptiacus (bat) Landing to Robotic Landing: Regulation of CG-CP Distance Using a Nonlinear Closed-Loop Feedback

Bats are unique in that they can achieve unrivaled agile maneuvers due to their functionally versatile wing conformations. Among these maneuvers, roosting (landing) has captured attentions because bats perform this acrobatic maneuver with a great composure. This work attempts to reconstruct bat landing maneuvers with a Micro Aerial Vehicle (MAV) called Allice. Allice is capable of adjusting the position of its Center of Gravity (CG) with respect to the Center of Pressure (CP) using a nonlinear closed-loop feedback. This nonlinear control law, which is based on the method of input-output feedback linearization, enables attitude regulations through variations in CG-CP distance. To design the model-based nonlinear controller, the Newton-Euler dynamic model of the robot is considered, in which the aerodynamic coefficients of lift and drag are obtained experimentally. The performance of the proposed control architecture is validated by conducting several experiments

Body Lift and Drag for a Legged Millirobot in Compliant Beam Environment

Much current study of legged locomotion has rightly focused on foot traction forces, including on granular media. Future legged millirobots will need to go through terrain, such as brush or other vegetation, where the body contact forces significantly affect locomotion. In this work, a (previously developed) low-cost 6-axis force/torque sensing shell is used to measure the interaction forces between a hexapedal millirobot and a set of compliant beams, which act as a surrogate for a densely cluttered environment. Experiments with a VelociRoACH robotic platform are used to measure lift and drag forces on the tactile shell, where negative lift forces can increase traction, even while drag forces increase. The drag energy and specific resistance required to pass through dense terrains can be measured. Furthermore, some contact between the robot and the compliant beams can lower specific resistance of locomotion. For small, light-weight legged robots in the beam environment, the body motion depends on both leg-ground and body-beam forces. A shell-shape which reduces drag but increases negative lift, such as the half-ellipsoid used, is suggested to be advantageous for robot locomotion in this type of environment.Comment: First three authors contributed equally. Accepted to ICRA 201

Evolutionary robotics in high altitude wind energy applications

Recent years have seen the development of wind energy conversion systems that can exploit the superior wind resource that exists at altitudes above current wind turbine technology. One class of these systems incorporates a flying wing tethered to the ground which drives a winch at ground level. The wings often resemble sports kites, being composed of a combination of fabric and stiffening elements. Such wings are subject to load dependent deformation which makes them particularly difficult to model and control. Here we apply the techniques of evolutionary robotics i.e. evolution of neural network controllers using genetic algorithms, to the task of controlling a steerable kite. We introduce a multibody kite simulation that is used in an evolutionary process in which the kite is subject to deformation. We demonstrate how discrete time recurrent neural networks that are evolved to maximise line tension fly the kite in repeated looping trajectories similar to those seen using other methods. We show that these controllers are robust to limited environmental variation but show poor generalisation and occasional failure even after extended evolution. We show that continuous time recurrent neural networks (CTRNNs) can be evolved that are capable of flying appropriate repeated trajectories even when the length of the flying lines are changing. We also show that CTRNNs can be evolved that stabilise kites with a wide range of physical attributes at a given position in the sky, and systematically add noise to the simulated task in order to maximise the transferability of the behaviour to a real world system. We demonstrate how the difficulty of the task must be increased during the evolutionary process to deal with this extreme variability in small increments. We describe the development of a real world testing platform on which the evolved neurocontrollers can be tested

Flying over the reality gap: From simulated to real indoor airships

Because of their ability to naturally float in the air, indoor airships (often called blimps) constitute an appealing platform for research in aerial robotics. However, when confronted to long lasting experiments such as those involving learning or evolutionary techniques, blimps present the disadvantage that they cannot be linked to external power sources and tend to have little mechanical resistance due to their low weight budget. One solution to this problem is to use a realistic flight simulator, which can also significantly reduce experimental duration by running faster than real time. This requires an efficient physical dynamic modelling and parameter identification procedure, which are complicated to develop and usually rely on costly facilities such as wind tunnels. In this paper, we present a simple and efficient physics-based dynamic modelling of indoor airships including a pragmatic methodology for parameter identification without the need for complex or costly test facilities. Our approach is tested with an existing blimp in a vision-based navigation task. Neuronal controllers are evolved in simulation to map visual input into motor commands in order to steer the flying robot forward as fast as possible while avoiding collisions. After evolution, the best individuals are successfully transferred to the physical blimp, which experimentally demonstrates the efficiency of the proposed approac

Engineering Dynamics and Life Sciences

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”