Controle dinâmico de robôs móveis com acionamento diferencial

This work addresses the dynamic control problem of two-wheeled differentially driven non-holonomic mobile robot. Strategies for robot positioning control and robot orientating control are presented. Such strategies just require information about the robot con¯guration (x, y and teta), which can be collected by an absolute positioning system. The strategies development is related to a change on the controlled variables for such systems, from x, y and teta to s (denoting the robot linear displacement) and teta, and makes use of the polar coordinates representation for the robot kinematic model. Thus, it is possible to obtain a linear representation for the mobile robot dynamic model and to develop such strategies. It is also presented that such strategies allow the use of linear controllers to solve the control problem. It is shown that there is flexibility to choice the linear controller (P, PI, PID, Model Matching techniques, others) to be implemented. This work presents an introduction to mobile robotics and their characteristics followed by the control strategies development and controllers design. Finally, simulated and experimental results are presented and commented

Sistema de navegação para robôs móveis autônomos

The main task and one of the major mobile robotics problems is its navigation process. Conceptualy, this process means drive the robot from an initial position and orientation to a goal position and orientation, along an admissible path respecting the temporal and velocity constraints. This task must be accomplished by some subtasks like robot localization in the workspace, admissible path planning, trajectory generation and motion control. Moreover, autonomous wheeled mobile robots have kinematics constraints, also called nonholonomic constraints, that impose the robot can not move everywhere freely in its workspace, reducing the number of feasible paths between two distinct positions. This work mainly approaches the path planning and trajectory generation problems applied to wheeled mobile robots acting on a robot soccer environment. The major dificulty in this process is to find a smooth function that respects the imposed robot kinematic constraints. This work proposes a path generation strategy based on parametric polynomials of third degree for the 'x' and 'y' axis. The 'theta' orientation is derived from the 'y' and 'x' relations in such a way that the generated path respects the kinematic constraint. To execute the trajectory, this work also shows a simple control strategy acting on the robot linear and angular velocities

Estratégias baseadas em aprendizado para coordenação de uma frota de robôs em tarefas cooperativas

In multi-robot systems, both control architecture and work strategy represent a challenge for researchers. It is important to have a robust architecture that can be easily adapted to requirement changes. It is also important that work strategy allows robots to complete tasks efficiently, considering that robots interact directly in environments with humans. In this context, this work explores two approaches for robot soccer team coordination for cooperative tasks development. Both approaches are based on a combination of imitation learning and reinforcement learning. Thus, in the first approach was developed a control architecture, a fuzzy inference engine for recognizing situations in robot soccer games, a software for narration of robot soccer games based on the inference engine and the implementation of learning by imitation from observation and analysis of others robotic teams. Moreover, state abstraction was efficiently implemented in reinforcement learning applied to the robot soccer standard problem. Finally, reinforcement learning was implemented in a form where actions are explored only in some states (for example, states where an specialist robot system used them) differently to the traditional form, where actions have to be tested in all states. In the second approach reinforcement learning was implemented with function approximation, for which an algorithm called RBF-Sarsa($lambda$) was created. In both approaches batch reinforcement learning algorithms were implemented and imitation learning was used as a seed for reinforcement learning. Moreover, learning from robotic teams controlled by humans was explored. The proposal in this work had revealed efficient in the robot soccer standard problem and, when implemented in other robotics systems, they will allow that these robotics systems can efficiently and effectively develop assigned tasks. These approaches will give high adaptation capabilities to requirements and environment changes.

Planejamento cooperativo de tarefas em um ambiente de futebol de robôs

Este trabalho apresenta o desenvolvimento de um método de coordenação e cooperação para uma frota de mini-robôs móveis. O escopo do desenvolvimento é o futebol de robôs. Trata-se de uma plataforma bem estruturada, dinâmica e desenvolvida no mundo inteiro. O futebol de robôs envolve diversos campos do conhecimento incluindo: visão computacional, teoria de controle, desenvolvimento de circuitos microcontrolados, planejamento cooperativo, entre outros. A título de organização os sistema foi dividido em cinco módulos: robô, visão, localização, planejamento e controle. O foco do trabalho se limita ao módulo de planejamento. Para auxiliar seu desenvolvimento um simulador do sistema foi implementado. O simulador funciona em tempo real e substitui os robôs reais. Dessa forma os outros módulos permanecem praticamente inalterados durante uma simulação ou execução com robôs reais. Para organizar o comportamento dos robôs e produzir a cooperação entre eles foi adotada uma arquitetura hierarquizada: no mais alto nível está a escolha do estilo de jogo do time; logo abaixo decide-se o papel que cada jogador deve assumir; associado ao papel temos uma ação específica e finalmente calcula-se a referência de movimento do robô. O papel de um robô dita o comportamento do robô na dada ocasião. Os papéis são alocados dinamicamente durante o jogo de forma que um mesmo robô pode assumir diferentes papéis no decorrer da partida

Modelagem linear e identificação do modelo dinâmico de um robô móvel com acionamento diferencial

This work presents a modelling and identification method for a wheeled mobile robot, including the actuator dynamics. Instead of the classic modelling approach, where the robot position coordinates (x,y) are utilized as state variables (resulting in a non linear model), the proposed discrete model is based on the travelled distance increment Delta_l. Thus, the resulting model is linear and time invariant and it can be identified through classical methods such as Recursive Least Mean Squares. This approach has a problem: Delta_l can not be directly measured. In this paper, this problem is solved using an estimate of Delta_l based on a second order polynomial approximation. Experimental data were colected and the proposed method was used to identify the model of a real robot

Uma proposta de metodologia para o ensino de Física usando robótica de baixíssimo custo

This paper presents methodology based on Lev Vigotsky`s social interactionist theory through investigative activities, which integrates the teaching of physics to robotics, directed to students of the Physics degree course, seeking to provide further training for future teachers. The method is organized through educational robotics workshops that addresses concepts of physics through the use of low-cost educational robots along with several activities. The methodology has been presented and discussed and put into practice afterwards in workshops so that these future teachers may be able to take robotics to their classroom. Students from the last and penultimate semester of the Physics degree course of the Federal Institute of Education, Science and Technology of Rio Grande do Norte, Caicó campus participated in this project

Ambiente de desenvolvimentoweb multiplataforma configurável para robótica educacional

We propose an online configurable multiplatform development environment specifically developed for educational robotics applications. The environment, which appears as an extension of RoboEduc software, allows the programming of several programmable robots to be performed using the R-Educ language. We make it possible for the user to program in the language R-Educ and then translate the code to a language previously registered, compiled and then sent or executed by the robot. To develop this work, we conducted a bibliographic research about the main programming languages used in robotics, as well as their definitions and paradigms, from which it was possible to define a set of patterns considered important for the creation of this environment. Then, in the software development phase, we implemented the development environment, bearing in mind the requirements and functionality defined in the design phase. Finally, to validate the platform, we conducted some trials of programming languages and verificate if the complete cycle was satisfied - registration of language, programming in R-Educ, compilation for the registered language, compilation to the machine code and send the code for the robot

Controle de posição com restrição à orientação de um Veículo Aéreo Não-Tripulado tipo Quadrirrotor

Quadrotors aircraft are composed by four propellers mounted on four engines on a cross or x disposition, and, in this structure, the engines on the same arm spin in the same direction and the other arm in the opposite direction. By rotating each helix generates vertical upward thrust. The control is done by varying the rotational speed of each motor. Among the advantages of this type of vehicle can cite the mechanical simplicity of construction, the high degree of maneuverability and the ability to have vertical takeoffs and landings. The modeling and control of quadrirrotores have been a challenge due to problems such as nonlinearity and coupling between variables. Several strategies have been developed to control this type of vehicle, from the classical control to modern. There are air surveillance applications where a camera is fixed on the vehicle to point forward, where it is desired that the quadrotor moves at a fixed altitude toward the target also pointing forward, which imposes an artificial constraint motion, because it is not desired that it moves laterally, but only forwards or backwards and around its axes . This restriction is similar to the naturally existing on robots powered by wheels with differential drive, which also can not move laterally, due to the friction of the wheels. Therefore, a position control strategy similar to that used in this type of robot could be adapted for aerial robots like quadrotor. This dissertation presents and discusses some strategies for the control of position and orientation of quadrotors found in the literature and proposes a strategy based on dynamic control of mobile robots with differential drive, called the variable reference control. The validity of the proposed strategy is demonstrated through computer simulations

Arquitetura de Software para Barcos Robóticos

We propose in this work a software architecture for robotic boats intended to act in diverse aquatic environments, fully autonomously, performing telemetry to a base station and getting this mission to be accomplished. This proposal aims to apply within the project N-Boat Lab NatalNet DCA, which aims to empower a sailboat navigating autonomously. The constituent components of this architecture are the memory modules, strategy, communication, sensing, actuation, energy, security and surveillance, making these systems the boat and base station. To validate the simulator was developed in C language and implemented using the graphics API OpenGL resources, whose main results were obtained in the implementation of memory, performance and strategy modules, more specifically data sharing, control of sails and rudder and planning short routes based on an algorithm for navigation, respectively. The experimental results, shown in this study indicate the feasibility of the actual use of the software architecture developed and their application in the area of autonomous mobile robotics

Desenvolvimento de um Sistema de Visão Global para uma Frota de Mini-Robôs Móveis

Navigation based on visual feedback for robots, working in a closed environment, can be obtained settling a camera in each robot (local vision system). However, this solution requests a camera and capacity of local processing for each robot. When possible, a global vision system is a cheapest solution for this problem. In this case, one or a little amount of cameras, covering all the workspace, can be shared by the entire team of robots, saving the cost of a great amount of cameras and the associated processing hardware needed in a local vision system. This work presents the implementation and experimental results of a global vision system for mobile mini-robots, using robot soccer as test platform. The proposed vision system consists of a camera, a frame grabber and a computer (PC) for image processing. The PC is responsible for the team motion control, based on the visual feedback, sending commands to the robots through a radio link. In order for the system to be able to unequivocally recognize each robot, each one has a label on its top, consisting of two colored circles. Image processing algorithms were developed for the eficient computation, in real time, of all objects position (robot and ball) and orientation (robot). A great problem found was to label the color, in real time, of each colored point of the image, in time-varying illumination conditions. To overcome this problem, an automatic camera calibration, based on clustering K-means algorithm, was implemented. This method guarantees that similar pixels will be clustered around a unique color class. The obtained experimental results shown that the position and orientation of each robot can be obtained with a precision of few millimeters. The updating of the position and orientation was attained in real time, analyzing 30 frames per second

O hipertexto eletrônico de meio ambiente : estratégias de leitura e navegação

The incorporation of computing in class instigate the use of the Internet and websites as a content support in the teaching/leaning process. This kind of practice had challenged the students to read through eletronic hypertextual means. In that way, we re trying to undestand which strategies of reading and navigation the students of the second and third grade of highschool levels are using when reading electronic hypertexts from the www.ambientebrasil.com.br website. The research took place in the Escola Estadual Jerônimo Rosado in Mossoró RN. Our theoretical base was estructured on the digital Technology (electronic hypertext estructure and it s navigation modes), in applied linguistics (act of reading) and in cognition (interaction of the reader with the text and the use of reading strategies in the virtual computing enviroment). The applied methodology was the case analysis which was developed with the reunion of collected data through qualitative reseach questionaries, direct observations and video recording sessions. The research demonstrates that reader s ability in the act of navigating on virtual sites activates his/her reading strategies. Also shows how the semantic architecture of the hyperlinks can interfere directly over the strategies of reading and navigation in specific websites. Our research also intend to demonstrate that the student use his strategies of linear text reading when are not accustomed to use the reading through websites in a regular basis. The investigation concludes observing that the amount of hypertexts per pages and the inappropriate use of the multimedia elements were harmful to the reading fluency

Avaliando o impacto da utilização de renderizações panorâmicas para a navegação em ambientes virtuais

Panoramic rendering is the visualization of three-dimensional objects in a virtual environment through a wide viewing angle. This work investigated if the use of panoramas is able to promote faster searches in a virtual environment. Panoramas allow the presentation of space through less need to change the orientation of the camera, especially for the case of projections spanning 360º surrounding the user, which can benefit searching. However, the larger the angle, more distorted is the visualization of the environment, causing confusion in navigation. The distortion is even bigger when the user changes the pitch of the camera, by looking up or down. In this work we developed a technique to eliminate specifically the distortions caused by changes in pitch, which was called hemispheric projection. Experiments were done to evaluate the performance of search navigation through perspective, cylindrical and hemispherical projections. The results indicate that navigating with perspective projection is superior than navigating with panoramic projections, possibly due to factors such as (i) lack of experience of the participants in understanding the scenes displayed as panoramas, (ii) the inherent presence of distortion in panoramic projections and (iii) a lower display resolution because the objects are presented in smaller sizes in panoramic projections, making the perception of details more difficult. However, the hemispherical projection was better than the cylindrical, indicating that the developed technique provides benefits for navigation compared to current techniques of panoramic projection. The hemispheric projection also provided the least amount of changes of camera orientation, which is an indication that the hemispheric projections may be particularly useful in situations where there are restrictions on the ease to change the orientation. Future research will investigate the performance of cameras interactions on slower devices, such as using only keyboard, or brain-machine interfaces