João Alberto Fabro

ROS Navigation: Concepts and Tutorial

This tutorial chapter aims to teach the main theoretical concepts and explain the use of ROS Navigation Stack. This is a powerful toolbox to path planning and Simultaneous Localization And Mapping (SLAM) but its application is not trivial due to lack of comprehension of the related concepts. This chapter will present the theory inside this stack and explain in an easy way how to perform SLAM in any robot. Step by step guides, example codes explained (line by line) and also real robot testing will be available. We will present the requisites and the how-to’s that will make the readers able to set the odometry, establish reference frames and its transformations, configure perception sensors, tune the navigation controllers and plan the path on their own virtual or real robots.

Notification-Oriented Paradigm Framework 2.0: An Implementation Based On Design Patterns

The Notification-Oriented Paradigm (NOP) is a new technique to develop software. NOP is a rule-oriented approach where every rule and fact-base element is derived into less complex entities with specific tasks. These entities particularly collaborate by means of notifications, which occur only when their state changes. This allows carrying out an inference process completely active. Due to this particular arrangement, NOP can eliminate most of the structural and temporal redundancies that affects program execution performance, difficulties in codification level, and high coupling in program modules. In order to validate the NOP state of art, a framework was initially implemented in C++. Even though it quite demonstrated the features of the paradigm in terms of the development process, it still presented a gap in execution performance. In this context, this paper presents the NOP Framework 2.0. This new version was reengineered aiming better structuration and improvements in the execution time of NOP applications. The experiments show that the new implementation is two times faster than the former one. In addition, new experiments were presented comparing the NOP applications to equivalent implementations based on Oriented-Object Paradigm (OOP) in C++. The NOP applications presented, in some cases, better performance than the OOP applications.

On using fuzzy logic to control a simulated hexacopter carrying an attached pendulum

Fuzzy logic is used in many applications from industrial process control to automotive applications, including consumers trend forecast, aircraft maneuvering control and others. Considering the increased interest in using of multi-rotor aircrafts (usually called drones) for many kinds of applications, it is important to study new methods to improve multi-rotor maneuverability while controlling its stability in a proper way. Controlling the flight of multi-rotors, specially those equipped six rotors, is not a trivial task. When considering the design of such a control systems, traditional approaches such as PD/PID are very difficult to design, in spite of being easily implementable. This work proposes an approach based on multiple interconnected fuzzy controllers, aiming to control the various aspects related to maneuverability of a hexacopter carrying a free payload forming a pendulum. The behavior produced by such a control system has been simulated on a well-known robotics simulation environment and analyzed in terms of flight stability, as well as roll, pitch and yaw movements. The results show the feasibility of the proposed approach in keeping the hexacopter flying in a stable way.

Cooperative load transport based on fuzzy logic controllers

This work presents the use of multiple mobile robots to perform a common transportation task. The main objective is to perform a navigation with a shared cargo, which allows the transport of objects with high payload or high sizes. Two robots are virtually linked through two Fuzzy controllers, one to control distance and another for orientation. A depth camera on the trailers robot is used to measure the distance and orientation of the leader robot. The proposed approach is experimentally validated with two standard Pioneer mobile robots that collaboratively carry a large box.

Training of an Artificial Neural Network with Backpropagation algorithm using notification oriented paradigm

When implementing Artificial Neural Networks with imperative programing languages, the resulting programs are usually highly coupled. This problem usually hampers distribution over multiple processors, especially when the ANN executes on general-purpose processors. An emerging technique called Notification Oriented Paradigm (NOP) facilitates the development of distributed and decoupled systems, and minimizes the amount of processing calculations, while avoiding structural and temporal redundancies in the logical-causal evaluation. These advantages seem to be relevant to parallel systems, especially in the case of ANNs. In this sense, this paper presents the development of a Multi-Layer Perceptron using Backpropagation training algorithm, based on the concepts of NOP in its implementation. The overall performance of NOP implementation was not so good in comparison with the Imperative Paradigm (IP) implementation, because the current materialization of NOP (framework) is still based on a single thread implementation. Even though, this implementation proved to be plausible and decoupled, as well as parallelizable according the inherent parallelism of ANNs, conceptually intrinsic on the NOP.

Collaborative Behavior in Soccer: The Setplay Free Software Framework

The Setplay Framework (available from SourceForge as free software) is composed of a C++ library (Project name: fcportugalsetplays), a fully functional RoboCup Simulation 2D demonstration team (fcportugalsetplaysagent2d), and a complete graphical tool (SPlanner), that can be used to design and plan the collaborative behavior between the soccer player agents. In order to demonstrate the usage of the Setplay library, a complete 2D simulation team, based on Agent2D, was developed. This example team uses the framework to execute previously planned collaborative behavior. This framework can be used both within simulated environments, such as the Robocup Soccer Simulation leagues, and with real soccer playing robots. This paper presents the free software Setplay Framework, and provides the necessary information for any team to use the framework with the goal of providing collaborative behavior to a team of soccer playing robots.

A Quadcopter and Mobile Robot Cooperative Task Using Visual Tags Based on Augmented Reality ROS Package

The objective of this chapter is to provide a simple tutorial on how to use a virtual reality tag (VR-TAG) tool and a Robot Operating System–compatible simulated multirotor vehicle to achieve the position of a small mobile ground robot, making possible the creation of a cooperative schema among them. The great novelty of the proposed architecture is that the ground robots do not have any onboard odometry, and all the position information is provided by the multirotor using a camera and the VR-TAGs to evaluate it. This kind of architecture poses value for real-world cooperative multiple robot research, in which the cost of constructing a large number of small robots makes practical applications inviable. In such cases, simple robots with minimal control hardware and sensors are a good alternative, and offboard positioning and control of these robots can be effective.

Proposal of a declarative and parallelizable artificial neural network using the notification-oriented paradigm

Since the 1960s, artificial neural networks (ANNs) have been implemented and applied in various areas of knowledge. Most of these implementations had their development guided by imperative programming (IP), usually resulting in highly coupled programs. Thus, even though intrinsically parallel in theory, ANNs do not easily take an effective distribution on multiple processors when developed under IP. As an alternative, the notification-oriented paradigm (NOP) emerges as a new programming technique. NOP facilitates the development of decoupled and distributed systems, using abstraction of knowledge through logical–causal rules, as well as the generation of an optimized code. Both features are possible by means of a notification-oriented inference process, which avoids structural and temporal redundancies in the logic–causal evaluations. These advantages are relevant to systems that have parts decoupled in order to run in parallel, such as ANN. In this sense, this work presents the development of a multilayer perceptron ANN using backpropagation training algorithm based on the concepts of a NOP implementation. Such implementation allows, transparently from high-level programming, parallel code generation that runs on multicore platforms. Furthermore, the solution based on NOP, when compared against the equivalent on IP, presents a high level of decoupling and explicit use of logic–causal elements, which are, respectively, useful to distribution, understanding and improvement of the application.

Simultaneous Navigation and Mapping in an Autonomous Vehicle Based on Fuzzy Logic

This research presents the navigation control and mapping of an autonomous car by fuzzy logic that enables automatic obstacle avoidance in unknown environments. The strategy is based on a map of the environment, which is created according to navigation, to plan the trajectories avoiding obstacles through the search algorithm A*. The proposed approach is evaluated in a virtual environment, where the autonomous car should move among different obstacles.

Designing Fuzzy Logic Controllers for ROS-Based Multirotors

This chapter presents a tutorial on using an open-source ROS package for implementing control systems based on Fuzzy Logic. Such a package has been created to facilitate the development of fuzzy control systems along with ROS technology and infrastructure. A step-by-step tutorial discusses how to develop a set of distributed and interconnected fuzzy controllers using the proposed ROS package. A fuzzy control system that controls the movement of an unmanned multirotor (specifically a hexacopter) is presented as case study. The behavior of this control system is demonstrated by means of a commercial robotics simulation environment named V-REP. One scenario is used to illustrate the fuzzy control system steering the movement of a virtual hexacopter carrying an attached loose payload, i.e. such a loose payload forms a pendulum. In this case study, one can see the hexacopter flight after receiving commands to fly to distinct positions within the scenario. It is important to highlight that, in order to be able to perform this tutorial, the reader must use ROS Indigo Igloo and V-REP PRO EDU version V3.3.0 both running on Ubuntu 14.04.4 LTS.