Sistemas de suporte à condução autónoma adequados a plataforma robótica 4-wheel skid-steer: percepção, movimento e simulação

As competições de robótica móvel desempenham papel preponderante na difusão da ciência e da engenharia ao público em geral. E também um espaço dedicado ao ensaio e comparação de diferentes estratégias e abordagens aos diversos desafios da robótica móvel. Uma das vertentes que tem reunido maior interesse nos promotores deste género de iniciativas e entre o público em geral são as competições de condução autónoma. Tipicamente as Competi¸c˜oes de Condução Autónoma (CCA) tentam reproduzir um ambiente semelhante a uma estrutura rodoviária tradicional, no qual sistemas autónomos deverão dar resposta a um conjunto variado de desafios que vão desde a deteção da faixa de rodagem `a interação com distintos elementos que compõem uma estrutura rodoviária típica, do planeamento trajetórias à localização. O objectivo desta dissertação de mestrado visa documentar o processo de desenho e concepção de uma plataforma robótica móvel do tipo 4-wheel skid-steer para realização de tarefas de condução autónoma em ambiente estruturado numa pista que pretende replicar uma via de circulação automóvel dotada de sinalética básica e alguns obstáculos. Paralelamente, a dissertação pretende também fazer uma análise qualitativa entre o processo de simulação e a sua transposição para uma plataforma robótica física. inferir sobre a diferenças de performance e de comportamento.Mobile robotics competitions play an important role in the diffusion of science and engineering to the general public. It is also a space dedicated to test and compare different strategies and approaches to several challenges of mobile robotics. One of the aspects that has attracted more the interest of promoters for this kind of initiatives and general public is the autonomous driving competitions. Typically, Autonomous Driving Competitions (CCAs) attempt to replicate an environment similar to a traditional road structure, in which autonomous systems should respond to a wide variety of challenges ranging from lane detection to interaction with distinct elements that exist in a typical road structure, from planning trajectories to location. The aim of this master’s thesis is to document the process of designing and endow a 4-wheel skid-steer mobile robotic platform to carry out autonomous driving tasks in a structured environment on a track that intends to replicate a motorized roadway including signs and obstacles. In parallel, the dissertation also intends to make a qualitative analysis between the simulation process and the transposition of the developed algorithm to a physical robotic platform, analysing the differences in performance and behavior

Generalized software application for operation of a 3D vehicle in air, water and land

The unmanned vehicles (UV) and its applications are growing exponentially. Using the radio control is the most common way to control these types of vehicles for being a simple and cheap method to control an UV. However, it doesn’t have a visual interface that allows the user to see the vehicle’s information such as battery status, speed, distance, geolocation, etc. To deal with this problem, some mobile and desktop applications have been developed. To communicate between the control device and the vehicle, dongles are commonly used to establish the connection using radio, Bluetooth or Wi-Fi. In most cases, these technologies don’t allow the user to control at long distances, Beyond Line Of-Sight (BLOS), and these applications are focused to use mostly on multi-copters, and most of the times, they only allow to connect a vehicle at a time. The purpose of this dissertation is to study the reliability of an application able to control multiple types of vehicles, such as aerial, land and water vehicles. This application allows the user to connect multiple vehicles at the same time using a single device, easily change the vehicle assigned to control, by using mobile networks to perform the communication between the developed application and the vehicle. In this way, it will be possible to connect a 3D – hybrid vehicle, which is a vehicle capable of moving in water, land and air environments, allowing the user to control the vehicle at long distances with video feedback. To achieve the purpose of this dissertation, it was developed an Android application to allow controlling the vehicle by using mobile networks to communicate. In the vehicle, besides the common electronics used in an unmanned vehicle (ESC’s, motors, batteries, controller board, etc.), it will be used a Raspberry Pi 2 model B with a 3rd Generation (3G) and 4th Generation (4G) dongle that will connect the vehicle to the internet, routing the messages coming from the controller board placed in the vehicle to the mobile application. It was also developed a server application to do the user management and exchange the messages coming from both platforms: vehicle and application.Os veículos não tripulados e as suas aplicações estão em forte crescimento. O uso de rádio controlo é a maneira mais comum de controlar estes tipos de veículos, sendo o método mais barato e simples de controlar um veículo não tripulado. Contudo, não têm uma interface visual que permita ao utilizador ver as informações do veículo, tais como o nível da bateria, a velocidade, distância, geolocalização, entre outros. Para ajudar com este problema, têm sido desenvolvidas algumas aplicações para dispositivos móveis e computadores, que permitem controlar e monitorizar este tipo de veículos. Para estabelecer a comunicação entre o dispositivo de controlo e o veículo, são frequentemente usados dongles para comunicar por rádio, Bluetooth ou Wi-Fi. Na maioria dos casos, estas tecnologias não possibilitam ao utilizador o controlo a longas distâncias, para além da linha de vista, e costumam ser focadas para o uso em multicopteros, possibilitando, na maioria dos casos, a ligação de um único veículo. O âmbito desta dissertação pretende estudar e desenvolver uma aplicação com elevada fiabilidade, capaz de controlar vários tipos de veículos, nomeadamente, veículos aéreos, terrestres e aquáticos. Esta aplicação irá permitir a ligação a vários veículos ao mesmo tempo, trocar facilmente o veiculo a controlar, recorrendo aos sistemas de comunicação móveis celulares, 3ª geração (3G ) e 4ª geração (4G) para garantir a comunicação entre a aplicação desenvolvida e o veículo não tripulado. Seguindo estes princípios, é possível controlar um veículo 3D hibrido (em modo de ar, terra e mar). Esta permite ao utilizador controlar o veículo a longas distâncias com o uso de uma transmissão de vídeo. Para alcançar o objetivo desta dissertação foi desenvolvida uma aplicação Android para possibilitar o controlo recorrendo às redes móveis celulares. No veículo, além da eletrónica habitual, para um veículo não tripulado (motores, ESC’s, baterias, etc.), será também utilizado um Raspberry Pi 2 modelo B com um dongle 3G/4G que liga o veículo, redirecionando as mensagens vindas da placa de controlo para a aplicação móvel. Para a comunicação entre a aplicação e o veículo foi também desenvolvida uma aplicação instalada no servidor que é responsável pela gestão de utilizadores e pela troca de mensagens vindas de ambas as plataformas: veículo e aplicação

Decentralized path planning for multiple agents in complex environments using rapidly-exploring random trees

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 89-94).This thesis presents a novel approach to address the challenge of planning paths for real-world multi-agent systems operating in complex environments. The technique developed, the Decentralized Multi-Agent Rapidly-exploring Random Tree (DMARRT) algorithm, is an extension of the CL-RRT algorithm to the multi-agent case, retaining its ability to plan quickly even with complex constraints. Moreover, a merit-based token passing coordination strategy is also presented as a core component of the DMA-RRT algorithm. This coordination strategy makes use of the tree of feasible trajectories grown in the CL-RRT algorithm to dynamically update the order in which agents plan. This reordering is based on a measure of each agent's incentive to replan and allows agents with a greater incentive to plan sooner, thus reducing the global cost and improving the team's overall performance. An extended version of the algorithm, Cooperative DMA-RRT, is also presented to introduce cooperation between agents during the path selection process. The paths generated are proven to satisfy inter-agent constraints, such as collision avoidance, and a set of simulation and experimental results verify the algorithm's performance. A small scale rover is also presented as part of a practical test platform for the DMA-RRT algorithm.by Vishnu R. Desaraju.S.M

System Development of an Unmanned Ground Vehicle and Implementation of an Autonomous Navigation Module in a Mine Environment

There are numerous benefits to the insights gained from the exploration and exploitation of underground mines. There are also great risks and challenges involved, such as accidents that have claimed many lives. To avoid these accidents, inspections of the large mines were carried out by the miners, which is not always economically feasible and puts the safety of the inspectors at risk. Despite the progress in the development of robotic systems, autonomous navigation, localization and mapping algorithms, these environments remain particularly demanding for these systems. The successful implementation of the autonomous unmanned system will allow mine workers to autonomously determine the structural integrity of the roof and pillars through the generation of high-fidelity 3D maps. The generation of the maps will allow the miners to rapidly respond to any increasing hazards with proactive measures such as: sending workers to build/rebuild support structure to prevent accidents. The objective of this research is the development, implementation and testing of a robust unmanned ground vehicle (UGV) that will operate in mine environments for extended periods of time. To achieve this, a custom skid-steer four-wheeled UGV is designed to operate in these challenging underground mine environments. To autonomously navigate these environments, the UGV employs the use of a Light Detection and Ranging (LiDAR) and tactical grade inertial measurement unit (IMU) for the localization and mapping through a tightly-coupled LiDAR Inertial Odometry via Smoothing and Mapping framework (LIO-SAM). The autonomous navigation module was implemented based upon the Fast likelihood-based collision avoidance with an extension to human-guided navigation and a terrain traversability analysis framework. In order to successfully operate and generate high-fidelity 3D maps, the system was rigorously tested in different environments and terrain to verify its robustness. To assess the capabilities, several localization, mapping and autonomous navigation missions were carried out in a coal mine environment. These tests allowed for the verification and tuning of the system to be able to successfully autonomously navigate and generate high-fidelity maps

Lunar Rover Motion Planning and Commands

Space exploration is moving forward and one of the topics currently being researched is mining. The objective of this thesis is to design and develop software for the auton- omous navigation of a wheeled rover that is being built for NASA’s Lunabotics Mining Competition. The motion control system is a crucial component of a planetary rover system and its implementation heavily depends on the chassis configuration. The configuration of the rover enables us to use three steering modes: Ackermann, Point- turn and Crab steering. The implementation takes advantages of all the modes and involves algorithms for path planning, path smoothing and path following. In addi- tion, the system offers a feature of automatic steering mode selection. The system can be tuned and controlled by the cross-platform application specifically developed for this purpose. The performance of the implemented system is analyzed by testing in a simulator with a realistic physics engine and 3D visualization capabilities. Our con- ducted tests confirm that the system is sufficient in the framework of the Lunabotics Mining Competition

Mobile Robot Path Following Controller Based On the Sirms Dynamically Connected Fuzzy Inference Model

This paper presents a simple and effective way to implement a path following controller for a differential drive wheeled mobile robot based on the single input rule modules (SIRMs) dynamically connected fuzzy inference model. The control of the mobile robot is divided into two control actions performed in parallel; the heading and the velocity controller. For the heading controller, each input item is assigned with a SIRM and a dynamic importance degree (DID). The velocity controller structure was modified to simplify the design and to fulfill the requirements of the path following method. Here, a common DID is used. The SIRMs and the dynamic importance degrees are designed such that the angular velocity control takes the highest priority over the linear velocity control of the mobile robot. By using the SIRMs and the dynamic importance degrees, the priority orders of the controls are automatically adjusted according to navigation situations. The proposed fuzzy controller has a simple and intuitively understandable structure, and executes the two control actions entirely in parallel. Simulation results show that the proposed fuzzy controller can drive a mobile robot smoothly with a high precision through a series of waypoints to attain its final target in short time

Unified Behavior Framework in an Embedded Robot Controller

Robots of varying autonomy have been used to take the place of humans in dangerous tasks. While robots are considered more expendable than human beings, they are complex to develop and expensive to replace if lost. Recent technological advances produce small, inexpensive hardware platforms that are powerful enough to match robots from just a few years ago. There are many types of autonomous control architecture that can be used to control these hardware platforms. One in particular, the Unified Behavior Framework, is a flexible, responsive control architecture that is designed to simplify the control system’s design process through behavior module reuse, and provides a means to speed software development. However, it has not been applied on embedded systems in robots. This thesis presents a development of the Unified Behavior Framework on the Mini-WHEGS™, a biologically inspired, embedded robotic platform. The Mini-WHEGS™ is a small robot that utilize wheel- legs to emulate cockroach walking patterns. Wheel-legs combine wheels and legs for high mobility without the complex control system required for legs. A color camera and a rotary encoder completes the robot, enabling the Mini-WHEGS™ to identify color objects and track its position. A hardware abstraction layer designed for the Mini-WHEGS™ in this configuration decouples the control system from the hardware and provide the interface between the software and the hardware. The result is a highly mobile embedded robot system capable of exchanging behavior modules with much larger robots while requiring little or no change to the modules

Mobile Robot Path Following Controller Based On the Sirms Dynamically Connected Fuzzy Inference Model

This paper presents a simple and effective way to implement a path following controller for a differential drive wheeled mobile robot based on the single input rule modules (SIRMs) dynamically connected fuzzy inference model. The control of the mobile robot is divided into two control actions performed in parallel; the heading and the velocity controller. For the heading controller, each input item is assigned with a SIRM and a dynamic importance degree (DID). The velocity controller structure was modified to simplify the design and to fulfill the requirements of the path following method. Here, a common DID is used. The SIRMs and the dynamic importance degrees are designed such that the angular velocity control takes the highest priority over the linear velocity control of the mobile robot. By using the SIRMs and the dynamic importance degrees, the priority orders of the controls are automatically adjusted according to navigation situations. The proposed fuzzy controller has a simple and intuitively understandable structure, and executes the two control actions entirely in parallel. Simulation results show that the proposed fuzzy controller can drive a mobile robot smoothly with a high precision through a series of waypoints to attain its final target in short time

Assessment of simulated and real-world autonomy performance with small-scale unmanned ground vehicles

Off-road autonomy is a challenging topic that requires robust systems to both understand and navigate complex environments. While on-road autonomy has seen a major expansion in recent years in the consumer space, off-road systems are mostly relegated to niche applications. However, these applications can provide safety and navigation to dangerous areas that are the most suited for autonomy tasks. Traversability analysis is at the core of many of the algorithms employed in these topics. In this thesis, a Clearpath Robotics Jackal vehicle is equipped with a 3D Ouster laser scanner to define and traverse off-road environments. The Mississippi State University Autonomous Vehicle Simulator (MAVS) and the Navigating All Terrains Using Robotic Exploration (NATURE) autonomy stack are used in conjunction with the small-scale vehicle platform to traverse uneven terrain and collect data. Additionally, the NATURE stack is used as a point of comparison between a MAVS simulated and physical Clearpath Robotics Jackal vehicle in testing