Connectivity Optimization in Robotic Networks

La collaboration entre multiple appareils électroniques (e.g. smartphones, ordinateurs, robots, senseurs et routeurs) est une tendance qui suscite un vif intérêt tant ses applications semblent prometteuses. Les maisons autonomes ou villes intelligentes figurent parmi la prodigieuse variété d’exemples. La communication entre appareils est une des clés du succès de leur coopération. Sans un bon système de communication, les appareils se retrouvent vite incapables d’échanger l’information nécessaire à la prise de décision. Pour garantir une bonne communication, il faut un réseau solide sur lequel elle puisse reposer. Nous pourrions envisager une organisation centralisée, puisqu’elles sont si répandues. Nos téléphones portables communiquent grâce à des antennes-relais ; et nous naviguons sur l’internet grâce à des routeurs. Dans un réseau centralisé, si un noeud principal, tel qu’une antenne ou un routeur, est défaillant, la capacité à communiquer en est dramatiquement diminuée. Or, certaines collaborations entre appareils interviennent, parfois, dans des situations où les infrastructures classiques ne sont pas accessibles. C’est le cas pour les opérations de sauvetages, où les moyens de communications classiques ont pu être endommagés à la suite d’un sinistre. D’autres organisations sont alors plus judicieuses. Dans les réseaux ad hoc, par exemple, il n’existe pas de noeud central, car chaque appareil peut servir au transit de l’information. Cette dissertation s’intéresse à la mise en place de réseaux ad hoc et mobiles entre smartphones et drones. Elle s’inscrit dans le cadre d’un partenariat, entre Humanitas Solutions et l’École Polytechnique de Montréal, qui vise à établir un moyen de communication basé sur ces appareils, pour connecter victimes et premiers secours lors d’opérations de sauvetages. Pour mener à bien ce projet, nous devons permettre aux appareils électroniques de communiquer sans recourir à quelconque infrastructure. Pour relayer l’information, nous devons également maintenir les drones connectés au-dessus de la zone sinistrée.----------ABSTRACT: Because of their promising applications, the interest for machine-to-machine interaction has soared (e.g. between smartphones, laptops, robots, sensors, or routers). Autonomous homes and smart cities are just two examples among the many. Without a good communication system, devices are unable to share relevant information and take effective decisions. Thus, inter-device communication is key for successful cooperations. To guarantee suitable communication, devices need to rely on a robust network. One might think of classical centralized network architecture since it is so common – antennae relay our smartphone communications, and routers provide us with an Internet connection at home. However, this architecture is not adequate for every application. When a central node (e.g. an antenna or a router) fails, it can cripple all the network. Moreover, fixed infrastructure is not always available, which is detrimental for applications like search and rescue operations. Hence, other network designs can be more suitable, like ad hoc networks, where there is no central node and every device can route information. This work aims at establishing mobile ad hoc networks between multiple devices for search and rescue operations. This thesis is framed by a partnership between Humanitas Solutions and École Polytechnique de Montréal, whose goal is to relay information between victims and first responders by the use of smartphones and flying robots (i.e. drones). For this purpose, we have to enable infrastructureless communications between devices and maintain drones connected over the disaster area

Decentralized Collision-Free Control of Multiple Robots in 2D and 3D Spaces

Decentralized control of robots has attracted huge research interests. However, some of the research used unrealistic assumptions without collision avoidance. This report focuses on the collision-free control for multiple robots in both complete coverage and search tasks in 2D and 3D areas which are arbitrary unknown. All algorithms are decentralized as robots have limited abilities and they are mathematically proved. The report starts with the grid selection in the two tasks. Grid patterns simplify the representation of the area and robots only need to move straightly between neighbor vertices. For the 100% complete 2D coverage, the equilateral triangular grid is proposed. For the complete coverage ignoring the boundary effect, the grid with the fewest vertices is calculated in every situation for both 2D and 3D areas. The second part is for the complete coverage in 2D and 3D areas. A decentralized collision-free algorithm with the above selected grid is presented driving robots to sections which are furthest from the reference point. The area can be static or expanding, and the algorithm is simulated in MATLAB. Thirdly, three grid-based decentralized random algorithms with collision avoidance are provided to search targets in 2D or 3D areas. The number of targets can be known or unknown. In the first algorithm, robots choose vacant neighbors randomly with priorities on unvisited ones while the second one adds the repulsive force to disperse robots if they are close. In the third algorithm, if surrounded by visited vertices, the robot will use the breadth-first search algorithm to go to one of the nearest unvisited vertices via the grid. The second search algorithm is verified on Pioneer 3-DX robots. The general way to generate the formula to estimate the search time is demonstrated. Algorithms are compared with five other algorithms in MATLAB to show their effectiveness