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This thesis presents the design and control of a cable-actuated mobile snake robot. The goal of this research is to reduce the size of snake robots and improve their locomotive efficiency by simultaneously actuating groups of links to fit optimized curvature profiles. The basic functional unit of the snake is a four-link, single degree of freedom module that bends using an antagonistic cable-routing scheme. Elastic elements in series with the cables and the coupled nature of the mechanism allow each module to detect and automatically respond to obstacles. The mechanical and electrical designs of the bending module are presented, with emphasis on the cable-routing scheme, key optimizations, and the use of series elastic actuation. An approximate expression for the propulsive force generated by a snake as a function of its articulation (i.e. the number of links it contains divided by its body length) is derived and a closed-form approximation for the optimal phase offset between joints to maximize the speed of a snake is obtained by simplifying a previous result. A simplified model of serpentine locomotion that considers the forces acting on a single link as it traverses a sinusoid is presented and compared to a detailed multibody dynamic model. Control strategies for snake robots with coupled joints are developed, along with a feedback linearization of the joint dynamics. Experimental studies of force control, locomotion, and adaptation to obstacles using a fully integrated prototype are presented and compared with simulated results. / MS

A homogeneous population of robots described as an Army-ant swarm is to be realized for material transportation. Robots envisioned in the Army-ant scenario are relatively small, independent autonomous mobile robots that can cooperatively carry palletized loads. In this thesis, the agents are treated as a self-organizing system of moving points. This characteristic makes the Army-ant swarm a modular, adaptive, and dynamic system. Several algorithms for the spatial self-organization of the robots are given. Self-organizing agents can arrange themselves geometrically in two- and three-dimensional space using only local information about teammates. The method is a distributed one: each agent uses only the information obtained by its own sensors. Algorithms are based on feasible assumptions. It is also shown possible to divide such a population into different groups around goals by communicating minimal data. Data transfer has a broadcast characteristic. Behavioral self-organization in the Army-ant scenario is also investigated. Activation and inhibition relations between robots determine the behavior (position in a behavioral space) of the agents, while in spatial self-organization force fields are in effect. Several problems which may be encountered and the solution to some of these problems are outlined. Methods for communication and cooperative decision systems — such as coupled van der Pol oscillators — in finding and carrying the pallets are proposed. Sensors and communication systems that may be used in the Army-ant scenario are also briefly discussed. / Master of Science

Les robots mobiles à roues orientables gagnent de la mobilité en employant des roues conventionnelles entièrement orientables, comportant deux joints actifs, un pour la direction et un autre pour la conduite. En dépit d'avoir seulement un degré de mobilité (DOM) (défini ici comme degrés de liberté instantanément autorisés DOF), correspondant à la rotation autour du centre de rotation instantané (ICR), ces robots peuvent effectuer des trajectoires planaires complexes de $ 2D $. Ils sont moins chers et ont une capacité de charge plus élevée que les roues non conventionnelles (par exemple, Sweedish ou Omni-directional) et, en tant que telles, préférées aux applications industrielles. Cependant, ce type de structure de robot mobile présente des problèmes de contrôle textit {basic} difficiles de la coordination de la direction pour éviter les combats d'actionneur, en évitant les singularités cinématiques (ICR à l'axe de la direction) et les singularités de représentation (du modèle mathématique). En plus de résoudre les problèmes de contrôle textit {basic}, cette thèse attire également l'attention et présente des solutions aux problèmes de textit {niveau d'application}. Plus précisément, nous traitons deux problèmes: la première est la nécessité de reconfigurer "de manière discontinue" les articulations de direction, une fois que la discontinuité dans la trajectoire du robot se produit. Une telle situation - la discontinuité dans le mouvement du robot - est plus susceptible de se produire de nos jours, dans le domaine émergent de la collaboration homme-robot. Les robots mobiles qui fonctionnent à proximité des travailleurs humains en mouvement rapide rencontrent généralement une discontinuité dans la trajectoire calculée en ligne. Le second apparaît dans les applications nécessitant que l'angle de l'angle soit maintenu, certains objets ou fonctionnalités restent dans le champ de vision (p. Ex., Pour les tâches basées sur la vision) ou les changements de traduction. Ensuite, le point ICR est nécessaire pour déplacer de longues distances d'un extrême de l'espace de travail à l'autre, généralement en passant par le centre géométrique du robot, où la vitesse du robot est limitée. Dans ces scénarios d'application, les contrôleurs basés sur l'ICR à l'état de l'art conduiront à des comportements / résultats insatisfaisants. Dans cette thèse, nous résolvons les problèmes de niveau d'application susmentionnés; à savoir la discontinuité dans les commandes de vitesse du robot et une planification meilleure / efficace pour le contrôle du mouvement du point ICR tout en respectant les limites maximales de performance des articulations de direction et en évitant les singularités cinématiques et représentatives. Nos résultats ont été validés expérimentalement sur une base mobile industrielle. / Steerable wheeled mobile robots gain mobility by employing fully steerable conventional wheels, having two active joints, one for steering, and another for driving. Despite having only one degree of mobility (DOM) (defined here as the instantaneously accessible degrees of freedom DOF), corresponding to the rotation about the instantaneous center of rotation (ICR), such robots can perform complex $2D$ planar trajectories. They are cheaper and have higher load carrying capacity than non-conventional wheels (e.g., Sweedish or Omni-directional), and as such preferred for industrial applications. However, this type of mobile robot structure presents challenging textit{basic} control issues of steering coordination to avoid actuator fighting, avoiding kinematic (ICR at the steering joint axis) and representation (from the mathematical model) singularities. In addition to solving the textit{basic} control problems, this thesis also focuses attention and presents solutions to textit{application level} problems. Specifically we deal with two problems: the first is the necessity to "discontinuously" reconfigure the steer joints, once discontinuity in the robot trajectory occurs. Such situation - discontinuity in robot motion - is more likely to happen nowadays, in the emerging field of human-robot collaboration. Mobile robots working in the vicinity of fast moving human workers, will usually encounter discontinuity in the online computed trajectory. The second appears in applications requiring that some heading angle is to be maintained, some object or feature stays in the field of view (e.g., for vision-based tasks), or the translation verse changes. Then, the ICR point is required to move long distances from one extreme of the workspace to the other, usually passing by the robot geometric center, where the feasible robot velocity is limited. In these application scenarios, the state-of-art ICR based controllers will lead to unsatisfactory behavior/results. In this thesis, we solve the aforementioned application level problems; namely discontinuity in robot velocity commands, and better/efficient planning for ICR point motion control while respecting the maximum steer joint performance limits, and avoiding kinematic and representational singularities. Our findings has been validated experimentally on an industrial mobile base.

In this thesis, questions of navigation, planning and control of real-world mobile robotic systems are addressed. Chapter II contains the first contribution in this thesis, which is a modification of the canonical two-layer hybrid architecture: deliberative planning on top, with reactive behaviors underneath. Deliberative is used to describe higher-level reasoning that includes experiential memory and regional or global objectives. Alternatively, reactive describes low-level controllers that operate on information spatially and temporally immediate to the robot. In the traditional architecture, information is passed top down, with the deliberative layer dictating to the reactive layer. Chapter II presents our work on introducing feedback in the opposite direction, allowing the behaviors to provide information to the planning module(s). The path planning problem, particularly as it as solved by the visibility graph, is addressed first in Chapter III. Our so-called oriented visibility graph is a combinatorial planner with emphasis on dynamic re-planning in unknown environments at the expensive of guaranteed optimality at all times. An example of single source planning -- where the goal location is known and static -- this approach is compared to related approaches (e.g. the reduced visibility graph). The fourth chapter further develops the work presented in the Chapter III; the oriented visibility graph is extended to the hierarchical oriented visibility graph. This work directly addresses some of the limitations of the oriented visibility graph, particularly the loss of optimality in the case where obstacles are non-convex and where the convex hulls of obstacles overlap. This results in an approach that is a kind of middle-ground between the oriented visibility graph which was designed to handle dynamic updates very fast, and the reduced visibility graph, an old standard in path planning that guarantees optimality. Chapter V investigates path planning at a higher level of abstraction. Given is a weighted colored graph where vertices are assigned a color (or class) that indicates a feature or quality of the environment associated with that vertex. The question is then asked, ``what is the globally optimal path through this weighted colored graph?' We answer this question with a mapping from classes and edge weights to a real number, and use Dijkstra's Algorithm to compute the best path. Correctness is proven and an implementation is highlighted.

Orientador: João Maurício Rosário / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T12:12:48Z (GMT). No. of bitstreams: 1 Mainardi_AugustoSeganfredo_M.pdf: 4938710 bytes, checksum: c6b32726ef03c92f5c518f1eaabdf37c (MD5) Previous issue date: 2010 / Resumo: Neste trabalho é proposto um sistema de navegação autônomo para dispositivos robóticos móveis capaz de operar e se adaptar a diferentes ambientes e condições, contribuindo para o desenvolvimento de uma navegação robusta e confiável. O sistema é baseado na arquitetura híbrida AuRA, assim, foi separado em quatro componentes: percepção do ambiente, localização e mapeamento, planejamento de movimento e execução da trajetória. A percepção do ambiente é o componente responsável em converter as leituras dos sensores em informações sobre o ambiente. Considerando os sensores usadas da plataforma robótica móvel ASURO, este componente baseia-se na informações obtidas através da odometria e dos sensores seguidores de linha, informando ao sistema a distância percorrida e a posição do robô em relação a pista a ser seguida. O mapeamento do sistema baseou-se em mapas topológicos devido ao baixo custo computacional necessário e à semelhança com a maneira humana de localizar-se, utilizando a odometria como sistema de localização do robô e sensores seguidores de linha para determinação de seu posicionamento. O planejamento de movimentos foi dividido em duas fases. No planejamento de caminho utilizou-se o algoritmo de Dijkstra para determinar por quais nós ele deve passar para atingir seu objetivo; e para o planejamento de trajetória utilizou-se uma abordagem baseada no caminho de Dubins. A execução da trajetória baseou-se no método de Motor-Schemas, onde as respostas dos atuadores são determinadas pela soma vetorial dos vetores resultantes de cada comportamento. Foram estudadas duas formas de comportamento: o de seguir o objetivo que utiliza o planejamento de movimento para determinar as velocidades dos atuadores; e o de seguir uma linha, que utiliza a percepção do ambiente para determinar as velocidades dos atuadores. As implementações experimentais foram realizadas a partir do ambiente de simulação DD&GP desenvolvido para o ambiente MATLABSimulink®, que permitiu a avaliação do sistema a partir de duas aplicações (transporte e inspeção) efetuada em três ambientes diferentes (fábrica, escritório e sistema de tubulação). Além disso, utilizou-se a plataforma robótica móvel ASURO para verificar a percepção do ambiente e validar os resultados encontrados nas simulações. Os resultados obtidos nas implementações experimentais foram satisfatórios e mostram que o sistema apresentado é promissor / Abstract: In this work is proposed an autonomous navigation system for mobile robotic devices able to operate and adapt to different environments and conditions, contributing to the development of a robust and reliable navigation system. The system is based on hybrid architecture AuRA, thus, it was separated into four components: Perceptions of the environment, Localization and Mapping, Motion planning and Trajectory execution. The perception of the environment is the component responsible for converting the readings in sensors in environmental information. Considering the sensors used in mobile robotics platform ASURO, this component is based on information obtained from odometry and line following sensors, informing the system the distance traveled and the robot's position in relation to the track to be followed. The mapping of the system is based on topological maps due low computational cost required and its resemblance to the human way of locating themselves and the use of little computer memory, using the odometry as robot's localization system and line following sensors to determine their placement. The Motion planning was divided into two phases. In path planning was used Dijkstra's algorithm to determine for which node the robot must pass to achieve your goal; and for trajectory planning was used an approach based on Dubins path. The trajectory execution is based on the method of motor-schemas, where the responses of the actuators are determined by the vector sum of the resulting vectors from each behavior. Were studied two forms of behaviors: follow the goal, which uses the motion planning to determine the velocity of actuators; and follow a line, which uses the perception of the environment to determine the velocity of actuators. The experimental implementations were realized from the simulation environment DD&GP developed for the MATLAB-Simulink ®, which allowed the evaluation of the system after two applications (transport and inspection) performed in three different environments (factory, office and piping system). In addition, was used the platform for mobile robotics ASURO to verify the perception of the environment and validate the results found in the simulations. The results obtained in experimental implementations were satisfactory and showed that the system presented is promising / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Recent emphasis has been placed on mobile robotics performing in unstructured environments. This realm of operations requires many different algorithms to interpret the various situations. This not only requires a system that is able to support, and facilitate, the fusion of the results, but it also needs to be tolerant of system errors. In modern operating systems, separate processes are able to fail without affecting other processes. Using this ability, along with fault tolerant inter-process communications, and supervisory process managers, allows the total system to continue to operate under adverse conditions. While this paper focuses primarily on the challenges faced by mobile robotics, the approach can be extended to a wide range of systems which must autonomously identify and adapt to failures/situations.

published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

The thesis implements a vision-based leader-follower tracking algorithm on a ground robot system. One camera is the only sensor installed the leader-follower system and is mounted on the follower. One sphere is the only feature installed on the leader. The camera identifies the sphere in the openCV Library and calculates the relative position between the follower and leader using the area and position of the sphere in the camera frame. A P controller for the follower and a P controller for the camera heading are built. The vision-based leader-follower tracking algorithm is verified according to the simulation and implementation.

Orientador: Suely Cunha Amaro Mantovani / Banca: Nobuo Oki / Banca: Carlos Aurélio Faria da Rocha / Resumo: A proposta deste trabalho consiste no desenvolvimento de um sistema de navegação de um robô móvel autônomo utilizando-se de técnicas da lógica fuzzy, aqui desenvolvida na linguagem de descrição de hardware, VHDL, e a sua implementação em uma placa DE2 do fabricante Altera, usando o software de desenvolvimento, Quartus II, do mesmo fabricante. O objetivo do sistema de navegação proposto é o de que o protótipo do robô caminhe sem colidir em nenhum obstáculo (ande para frente, para esquerda, para direita e pare) usando para comunicação externa com o ambiente, três sensores de distância localizados um em cada lado do robô e um na frente, atuando através dessas informações em dois motores de passo. Os resultados desta implementação obtidos em simulação são satisfatórios e foram comparados aos resultados obtidos como o mesmo processo no MATLAB. / Abstract: The purpose of this work is to develop a navigation system of an autonomous mobile robot using fuzzy logic techniques, developed here in the hardware description language, VHDL, and its implementation on a DE2 - Altera board manufacturer, using the software development Quartus II, from the same manufacturer. The navigation system proposed in this work aims that the prototype robot rides without bumping into any obstacles (goes forward, to the left, to the right and stop) using for communication with the external environment three distance sensors, located one on each side of the robot and one at the front and acting through these information in two stepper motors. Simulation results obtained in the implementation developed here are reasonable compared to the same process done in MATLAB. / Mestre