Studies of minimalist multi-robot systems consider multiple robotic agents, each with limited individual capabilities, but with the capacity for self-organization in order to collectively perform coordinated tasks. Object clustering is a widely studied task in which self-organized robots form piles from dispersed objects. Our work considers a variation of an object clustering derived from the influential ant-inspired work of Beckers, Holland and Deneubourg which proposed stigmergy as a design principle for such multi-robot systems. Since puck mechanics contribute to cluster accrual dynamics, we studied a new scenario with square objects because these pucks into clusters differently from cylindrical ones. Although central clusters are usually desired, workspace boundaries can cause perimeter cluster formation to dominate. This research demonstrates successful clustering of square boxes - an especially challenging instance since flat edges exacerbate adhesion to boundaries - using simpler robots than previous published research. Our solution consists of two novel behaviours, Twisting and Digging, which exploit the objects’ geometry to pry boxes free from boundaries. Physical robot experiments illustrate that cooperation between twisters and diggers can succeed in forming a single central cluster. We empirically explored the significance of different divisions of labor by measuring the spatial distribution of robots and the system performance. Data from over 40 hours of physical robot experiments show that different divisions of labor have distinct features, e.g., one is reliable while another is especially efficient.

Autonomous robots like household service robots, self-driving cars and dronesare emerging as important parts of our daily lives in the near future. They need tocomprehend and fulfill complex tasks specified by the users with minimal humanintervention. Also they should be able to handle un-modeled changes and contingentevents in the workspace. More importantly, they shall communicate and collaboratewith each other in an efficient and correct manner. In this thesis, we address theseissues by focusing on the distributed and hybrid control of multi-robot systemsunder complex individual tasks. We start from the nominal case where a single dynamical robot is deployed in astatic and fully-known workspace. Its local tasks are specified as Linear TemporalLogic (LTL) formulas containing the desired motion. We provide an automatedframework as the nominal solution to construct the hybrid controller that drives therobot such that its resulting trajectory satisfies the given task. Then we expand theproblem by considering a team of networked dynamical robots, where each robot hasa locally-specified individual task also as LTL formulas. In particular, we analyzefour different aspects as described below. When the workspace is only partially known to each robot, the nominal solutionmight be inadequate. Thus we first propose an algorithm for initial plan synthesis tohandle partially infeasible tasks that contain hard and soft constraints. We designan on-line scheme for each robot to verify and improve its local plan during runtime, utilizing its sensory measurements and communications with other robots. Itis ensured that the hard constraints for safety are always fulfilled while the softconstraints for performance are improved gradually. Secondly, we introduce a new approach to construct a full model of both robotmotion and actions. Based on this model, we can specify much broader robotic tasksand it is used to model inter-robot collaborative actions, which are essential for manymulti-robot applications to improve system capability, efficiency and robustness.Accordingly, we devise a distributed strategy where the robots coordinate theirmotion and action plans to fulfill the desired collaboration by their local tasks. Thirdly, continuous relative-motion constraints among the robots, such as collision avoidance and connectivity maintenance, are closely related to the stability,safety and integrity of multi-robot systems. We propose two different hybrid controlapproaches to guarantee the satisfaction of all local tasks and the relative-motionconstraints at all time: the first one is based on potential fields and nonlinear controltechnique; the second uses Embedded Graph Grammars (EGGs) as the main tool. At last, we take into account two common cooperative robotic tasks, namelyservice and formation tasks. These tasks are requested and exchanged among therobots during run time. The proposed hybrid control scheme ensures that the real-time plan execution incorporates not only local tasks of each robot but also thecontingent service and formation tasks it receives. Some of the theoretical results of the thesis have been implemented and demonstrated on various robotic platforms. / Denna avhandling fokuserar på distribuerad och hybridstyrning av multi-robot-system för komplexa, lokala och tidsberoende uppgifter. Dessa uppgifter specificerasav logiska formler rörande robotens rörelser och andra ageranden. Avhandlingenbehandlar ett tvärvetenskapligt område som integrerar reglering av nätverkaderobotsystem och planering baserad på formella metoder. Ett ramverk för hybridstyrning av flera dynamiska robotar med lokalt specificerade uppgifter presenteras.Fyra huvudscenarier betraktas: (1) robot-planering med motstridiga arbetsuppgifterinom ett delvis okänt arbetsområde; (2) beroende uppgifter för en grupp heterogenaoch samverkande robotar; (3) relativa rörelsebegränsningar hos varje robot; samt(4) robotar med uppgifter som begärs och bekräftas under körning. Numeriskasimuleringar och experiment visas för att validera de teoretiska resultaten. / <p>QC 20151204</p> / EU STREP RECONFIG: FP7-ICT-2011-9-600825 / Swedish Research Council (VR)

In this thesis, we examine algorithms for the division of labour in a group of robot. The algorithms make no use of direct communication. Instead, they are based only on the interactions among the robots and between the group and the environment. Division of labour is the mechanism that decides how many robots shall be used to perform a task. The efficiency of the group of robots depends in fact on the number of robots involved in a task. If too few robots are used to achieve a task, they might not be successful or might perform poorly. If too many robots are used, it might be a waste of resources. The number of robots to use might be decided a priori by the system designer. More interestingly, the group of robots might autonomously select how many and which robots to use. In this thesis, we study algorithms of the latter type. The robotic literature offers already some solutions, but most of them use a form of direct communication between agents. Direct, or explicit, communication between the robots is usually considered a necessary condition for co-ordination. Recent studies have questioned this assumption. The claim is based on observations of animal colonies, e.g., ants and termites. They can effectively co-operate without directly communicating, but using indirect forms of communication like stigmergy. Because they do not rely on communication, such colonies show robust behaviours at group level, a condition that one wishes also for groups of robots. Algorithms for robot co-ordination without direct communication have been proposed in the last few years. They are interesting not only because they are a stimulating intellectual challenge, but also because they address a situation that might likely occur when using robots for real-world out-door applications. Unfortunately, they are still poorly studied. This thesis helps the understanding and the development of such algorithms. We start from a specific case to learn its characteristics. Then we improve our understandings through comparisons with other solutions, and finally we port everything into another domain. We first study an algorithm for division of labour that was inspired by ants' foraging. We test the algorithm in an application similar to ants' foraging: prey retrieval. We prove that the model used for ants' foraging can be effective also in real conditions. Our analysis allows us to understand the underlying mechanisms of the division of labour and to define some way of measuring it. Using this knowledge, we continue by comparing the ant-inspired algorithm with similar solutions that can be found in the literature and by assessing their differences. In performing these comparisons, we take care of using a formal methodology that allows us to spare resources. Namely, we use concepts of experiment design to reduce the number of experiments with real robots, without losing significance in the results. Finally, we apply and port what we previously learnt into another application: Sensor/Actor Networks (SANETs). We develop an architecture for division of labour that is based on the same mechanisms as the ants' foraging model. Although the individuals in the SANET can communicate, the communication channel might be overloaded. Therefore, the agents of a SANET shall be able to co-ordinate without accessing the communication channel.

This thesis examines the use of multiple robots in cooperative simultaneous localization and mapping (SLAM), where each robot must estimate the poses of all robots in the team, along with the positions of all known landmarks. The robot team must operate under the condition that the communication network between robots is never guaranteed to be fully connected. Under this condition, a novel algorithm is derived that allows each robot to obtain the centralized-equivalent estimate in a decentralized manner, whenever possible. The algorithm is then extended to a decentralized and distributed approach where robots share the computational burden in considering different data association hypotheses in generating the centralized-equivalent consensus estimate.

This thesis examines the use of multiple robots in cooperative simultaneous localization and mapping (SLAM), where each robot must estimate the poses of all robots in the team, along with the positions of all known landmarks. The robot team must operate under the condition that the communication network between robots is never guaranteed to be fully connected. Under this condition, a novel algorithm is derived that allows each robot to obtain the centralized-equivalent estimate in a decentralized manner, whenever possible. The algorithm is then extended to a decentralized and distributed approach where robots share the computational burden in considering different data association hypotheses in generating the centralized-equivalent consensus estimate.

In this thesis, we are addressing new method of object transportation using multi-robot system. The new method of object transportation is called A grid-based cyclic robot allocation (GCRA) method which consists multiple spherical robots. The object is placed on top of group of spherical robots before the transportation. The rotation of the multiple spherical robots cause the displacement of the object and reach the goal location based on the direction and speed of the rotation of the robots. The GCRA method for spherical robots is proposed along with specific stability criterion, which designs the formation of the multi-robot system. The formation is created based on the customized grid which is to be modified based on the properties of the object. The shape and the center of gravity of the shape define the horizontal gap, $g_x$ and vertical gap, $g_y$. All the possible locations of spherical robots is the cross points of grid which implies that $g_x$ and $g_y$ defines the distance between the robots and based on the boundary of the robots placed underneath the object, the condition of the stability is defined. It also identifies minimum number of robots required based on the arbitrary shape of an object for stable omni-directional translation of the object on a 2 dimensional space. The desired positions and formation of the robots is identified based goal position of the object. Under centralized system, position control is applied to drive the robots to the desired positions. The position control simultaneously makes the object mobile and maintain the stability of the object. Mathematical proof of the proposed method is shown verifying the stability of the transportation process with the assumptions of no slip between the robots and the object. 2 Dimensional Simulation results of robot allocation using GCRA for several arbitrary shapes certify the proposed method.

No description available.

Méthodologie de Conception de Système Multi-robots : de la Simulation à la Démonstration. Les systèmes multi-robots sont des systèmes complexes mais prometteurs dans de nombreux domaines, les nombreux travaux académiques dans ce domaine attestent de l'importance qu'ils auront dans le futur. Cependant, si ces promesses sont réelles, elles ne sont pas encore réalisées comme en témoigne le faible nombre de systèmes multi-robots utilisés dans l'industrie. Pourtant des solutions existent afin de permettre aux industriels et académiques de travailler ensemble à cette problématique. Nous proposons un état de l'art et les défis associés à la conception des systèmes multi-robots d'un point de vue académique et industriel. Nous présentons ensuite trois contributions pour la conception de ces systèmes : une réalisation d'un essaim hétérogène en tant que cas d'étude pratique afin de mettre en évidence les obstacles de conception. La modification d'un autopilote et d'un simulateur pour les rendre compatibles aux développements des systèmes multi-robots. La démonstration d'un outil d'évaluation sur la base des deux contributions précédentes. Enfin, nous concluons sur la portée de ces travaux et des perspectives à venir sur la base de l'open source / Multi-robot System Design Methodology : from Simulation to Demonstration Multi-robot systems are complex but promising systems in many fields, the number of academic works in this field underlines the importance they will have in the future. However, while these promises are real, they have not yet been realized, as evidenced by the small number of multi-robot systems used in the industry. However, solutions exist to enable industrialists and academics to work together on this issue. We propose a state of the art and challenges associated with the design of multi-robot systems from an academic and industrial point of view. We then present three contributions for the design of these systems: a realization of a heterogeneous swarm as a practical case study in order to highlight the design obstacles. The modification of an autopilot and a simulator to make them compatible with the development of multi-robot systems. Demonstration of an evaluation tool based on the two previous contributions. Finally, we conclude on the scope of this work and future perspectives based on open source.

No description available.

Orientador: Prof. Dr. Wagner Tanaka Botelho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência da Computação, 2017. / Os avanços tecnológicos realizados na robótica móvel ao longo do tempo requereram o estudo e desenvolvimento de robôs cada vez mais autônomos e complexos, capazes de se adaptarem aos ambientes e condições que lhe são impostas. Contudo, dependendo do objetivo a alcancar, torna-se mais efetivo a utilização de uma maior quantidade de robos menores e mais simples, com capacidade cooperativa, resultando em um sistema escalavel e menos suscetývel a falhas gerais, denominado Sistema Multirrobotico (SMR). Tendo um SMR como objeto de estudo principal, este trabalho consiste no desenvolvimento de uma arquitetura multirrobotica descentralizada para o controle de posição e formação utilizando quadricopteros. A arquitetura é composta por n quadricopteros virtuais, implementados no software de simulação Gazebo e um quadricoptero real. O Robot Operating System (ROS) controla todos os quadricopteros, alem de gerenciar a comunicação entre os agentes roboticos. Um ponto importante é que, visando a diminuição dos custos do projeto, foi utilizado apenas um quadricoptero real, uma vez que somente um é necessário para validar a integração entre os mundos virtual e real. Para o controle de posição e formação foram propostos modelos matematicos que determinam as trajetorias dos n quadricopteros em formação linear, formação de figuras poligonais com troca de posição e formação de figuras poligonais com troca de posição e ponto de referencia movel. Nas simulações, foi possivel observar o deslocamento dos quadic'opteros em formação, validando os modelos matematicos. Por'em, no experimento real, a trajetoria no controle de formação foi parcialmente observada devido a alguns problemas apresentados na estrutura do quadricoptero e tambem por não possuir um sistema de sensoriamento no ambiente real. Apesar desses problemas, a integração entre os mundos virtual e real também foi validada. / The technological advances made in mobile robotics over time have required the study and development of robots that are increasingly autonomous and complex, capable of adapting to the environments and conditions that are imposed on them. However, depending on the goal to be achieved, it becomes more e.ective to use a larger number of smaller and simpler robots with cooperative capability, resulting in a scalable system that is less susceptible to general failures, called Multi-Robot Systems (MRS). Considering a MRS as the main study, the main target in this work is to develop a descentralized multi-robot architecture for position control using quadcopters. The architecture consists of n virtual quadcopters, implemented on the Gazebo simulation software and a real quadcopter. The Robot Operating System (ROS) controls all quadcopters as well as managing communication between them. In order to reduce the project costs, only one real quadcopter was used, since it is enough to validate the integration between the virtual and real worlds. The mathematical models were proposed to calculate the paths of the quadcopters in linear formation, formation of polygonal figures with rotation and formation of polygonal figures with rotation and mobile reference point. In the simulations, it was possible to observe the displacement of the quadcopters in formation, validating the mathematical models. However, in the real experiment, the trajectory in the formation control was partially observed due to some limitations presented on the quadcopter structure. Also, the sensing system was not available in the real environment. Despite these problems, the integration between the virtual and real worlds has also been validated.