Simultaneous Auctions for "Rendez-Vous" Coordination Phases in Multi-robot Multi-task Mission

International audienceThis paper presents a protocol that permits to automatically allocate tasks, in a distributed way, among a fleet of agents when communication is not permanently available. In cooperation settings when communication is available only during short periods, it is difficult to build joint policies of agents to collectively accomplish a mission defined by a set of tasks. The proposed approach aims to punctually coordinate the agents during "Rendezvous'' phases defined by the short periods when communication is available. This approach consists of a series of simultaneous auctions to coordinate individual policies computed in a distributed way from Markov decision processes oriented by several goals. These policies allow the agents to evaluate their own relevance in each task achievement and to communicate bids when possible. This approach is illustrated on multi-mobile-robot missions similar to distributed traveling salesmen problem. Experimental results (through simulation and on real robots) demonstrate that high-quality allocations are quickly computed

Punctual versus continuous auction coordination for multi-robot and multi-task topological navigation

International audienceThis paper addresses the interest of using Punctual versus Continuous coordination for mobile multi-robot systems where robots use auction sales to allocate tasks between them and to compute their policies in a distributed way. In Continuous coordination, one task at a time is assigned and performed per robot. In Punctual coordination, all the tasks are distributed in Rendezvous phases during the mission execution. However , tasks allocation problem grows exponentially with the number of tasks. The proposed approach consists in two aspects: (1) a control architecture based on topo-logical representation of the environment which reduces the planning complexity and (2) a protocol based on Sequential Simultaneous Auctions (SSA) to coordinate Robots' policies. The policies are individually computed using Markov Decision Processes oriented by several goal-task positions to reach. Experimental results on both real robots and simulation describe an evaluation of the proposed robot architecture coupled wih the SSA protocol. The efficiency of missions' execution is empirically evaluated regarding continuous planning

Calcul distribué de politiques d'exploration pour une flotte de robots mobiles

National audienceCe papier présente une architecture multirobots permettant une allocation automatique de plusieurs objectifs sur une flotte de robots. Le challenge consiste à rendre des robots autonomes pour réaliser coopérativement leur mission sans qu'un plan soit prédéfini. Cette architecture, appelée PRDC, est basée sur 4 modules (Perception, Représentation, Délibération et Contrôle). Nous nous intéressons plus particulièrement au module de délibération en considérant le problème des voyageurs de commerce coopératifs dans un environnement incertain. L'objectif des robots est alors de visiter un ensemble de points d'intérêt représentés dans une carte topologique stochastique (Road-Map). Le processus proposé pour la construction des politiques collaboratives est distribué. Chaque robot calcule ses politiques individuelles possibles de façon à négocier collectivement l'allocation des points d'intérêt entre les membres de la flotte. Enfin, l'approche est évaluée via un important nombre de simulation

Towards Enabling Human-Robot Collaboration in Industry: Identification of Current Implementation Barriers

Human-robot collaboration (HRC) is designed to combine the repeatability and precision of robots with the flexibility and adaptability of human workers. However, despite being researched for several years, HRC applications are still not broadly adopted in the industry. This study aims to identify current barriers to HRC adoption in the industry from a practical perspective. Therefore, a qualitative explorative approach based on semi-structured interviews with knowledgeable industry experts was chosen. The study was conducted in cooperation between IMT Nord Europe and the Technical University of Munich in France and Germany. Thereby, several experts from various backgrounds in areas such as robot manufacturing, system integration, and robot application in manufacturing were interviewed. These interviews are inductively analysed, and the findings are compared to the state-of-the-art in scientific HRC research. The study offers insights into the practical barriers to HRC adoption resulting from the technical, economic, social, and normative dimensions as well as the trade-offs between them. Based on these insights, opportunities for future research are identified

Map Partitioning to Approximate an Exploration Strategy in Mobile Robotics

International audienceIn this paper, an approach is presented to automatically allocate a set of exploration tasks between a fleet of mobile robots. The approach combines a Road-Map technique and Markovian Decision Processes (MDPs). The addressed problem consists of exploring an area where a set of points of interest characterizes the main positions to be visited by the robots. This problem induces a long term horizon motion planning with a combinatorial explosion. The Road-Map allows the robots to represent their spatial knowledge as a graph of way-points connected by paths. It can be modified during the exploration mission requiring the robots to use on-line computations. By decomposing the Road-Map into regions, an MDP allows the current group leader to evaluate the interest of each robot in every single region. Using those values, the leader can assign the exploration tasks to the robots

Management tools to study and to deal with effects of climate change on inland waterways

Inland navigation transport takes part in the Trans-European network program (TEN-T ), which aims at promoting this mode of transport by creating favorable conditions for the further development of this sector. The NAIADES Action Program comprises numerous actions and measures to boost transport on inland waterways. Among these actions, the infrastructure issue is dealt with. It requires the inventory of the existing infrastructure and the study of the possible effects of the expected climate change. This was one of the objectives of the GEPET-Eau project (2013-2016), which led to the proposal of multi-scale modeling approaches and adaptive and predictive control architectures. The resilience of inland waterways against the increase of navigation demand and the expected extreme drought and flood events was studied by considering deterministic models. The proposed architecture is suitable to consider two scales of space and time to optimize the water resource allocation among the inland networks and to guarantee the navigation conditions by proposing advanced control and fault detection tools. These approaches, which were designed by considering inland waterways in the north of France, are still being improved. Indeed, it is firstly necessary to consider all the uncertainties that are inherent to large-scale and environmental systems. Secondly, the advanced control and fault detection tools require further development to deal with the very complex dynamics that characterize inland waterways. The main objective of this work is to present the current state of the tools that have been developed in order to study and manage the inland waterways in a climate change context. The global framework that allows describing the link between these two management scales will be detailed. The water resource allocation approach can be based on three different techniques: the Constraint Satisfaction Problem (CSP), the quadratic optimization and the Markov Decision Process (MDP). The MDP-based approach will be emphasized due to its suitability to study complex systems with uncertainties, and its main advantages and drawbacks will be discussed and compared to the other techniques. Advanced control and fault detection tools require an in-depth knowledge of the inland waterway dynamics. Characteristics of navigation reaches, i.e. slope, resonance phenomenon, uncontrolled inputs and interconnections, need to be taken into account. A big effort has been made to improve the modeling step of the navigation reaches by considering the IDZ (Integrator Delay Zero) model. The designed tools are based on this accurate model, and they aim at improving the water level control of each reach of the inland waterways and at performing predictive maintenance strategies by detecting, isolating and forecasting faults on sensors and actuators (limnimeters, gates, locks, etc.). The designed management tools will be presented by considering a part of the real inland navigation network in the north of France. Perspectives and future developments will be described. Peer Reviewed Document type: Articl

Constraint satisfaction problem based on flow graph to study the resilience of inland navigation networks in a climate change context

The T-Ten European program aims at optimizing the transport logistics in Europe by promoting alternative transport modes. Navigation transport offers a competitive and environmentally friendly alternative. Hence, it is foresaw an increase of the navigation transport demand that it will be necessary to accommodate. This will be very challenging particularly in a global change context where less available water resource is expected. A constraint satisfaction problem based on flow graph is proposed in this paper to study the resilience of inland navigation networks against increase of the navigation demand and extreme events. Drought and flood scenarios are simulated considering an network composed of five interconnected navigation reaches. The results show that the designed tools are adapted to the resilience study of inland navigation networks

Stratégie coopérative pour la mise en œuvre d'une flotte de robots mobiles dans un milieu ouvert et encombré

The work presented in this thesis aims to implement a fleet of robots to explore an open and crowded environment. The objective is to propose strategies allowing the robots to be autonomous in the calculation of decentralized policies and in the implementation of their tasks. The expected solution should allow each robot to act without being affected by any loss of communication. A set of points to visit should be allocated between the robots whenever it is necessary and communication is possible.As a first step, we proposed an architecture based on a topological representation of the environment to generate maps of low density. The aim is to reduce planification calculation costs by reducing the useful information and ensure that the assumptions respect the structural capacities of the robots in a real environment. The second contribution proposes an aproximate solution that helps in solving, during a mission, a problem that is similar to a stochastic traveling salesman. The solution is to decompose a multi-goal Markov decision process to overcome the limitation of the number of considered goals. Finally, distributing the resolution over several robots requires defining protocols to quickly allocate the set of goals. The proposed solution converges rapidly through successive simultaneous rounds of auctions based on an individual assessment of correlated preferences on the objectives.The experiments aim to evaluate statistically the quality of the solutions produced and the ability to deal, online, with problems of real size. These experiments are used to validate the proposed approaches in multi-robot frameworks.Les travaux réalisés dans le cadre de cette thèse visent à la mise en œuvre d'une flotte de plusieurs robots pour l'exploration d'un environnement ouvert et encombré. L'objectif consiste à proposer des stratégies permettant au groupe de robots d'être autonome dans le calcul des politiques décentralisées et dans la réalisation de leurs tâches respectives. La solution attendue doit permettre à chacun d'évoluer en étant affecté au minimum par une perte de communication. Les zones à visiter doivent alors être allouées entre les robots à chaque fois qu'il est nécessaire et que les robots sont en capacité de communiquer.Dans un premier temps, il est proposé une architecture basée sur une représentation topologique sémantique de l'environnement de façon à générer des cartes de faible densité. L'objectif est double : alléger les charges de calcul pour la planification en diminuant les données utiles et garantir que les hypothèses mises en œuvres respectent les capacités structurelles des robots dans un environnement réel. La seconde contribution propose une planification approchée sur plusieurs niveaux de façon à résoudre, en cours de mission, une problématique qui s'apparente à un voyageur de commerce stochastique. La solution consiste à décomposer un processus décisionnel de Markov orienté par plusieurs objectifs de façon à s'affranchir d'une limite sur le nombre d'objectifs considérés. Enfin, distribuer cette solution pour une résolution multi-robots nécessite la mise en place de protocoles permettant d'allouer rapidement l'ensemble de tous les objectifs. Sur la base d'une évaluation individuelle des préférences corrélées sur les objectifs, la solution distribuée proposée converge rapidement sur un consensus à travers une succession de ventes aux enchères simultanées.Les expérimentations réalisées visent à une évaluation statistique de la qualité des solutions produites ainsi que la possibilité de traiter des problématiques de taille réelle, en cours de mission. Elles permettent de valider les approches proposées dans un cadre multi-robots

MDP à grande échelle : étude de cas des voies navigables

National audienceInland waterway networks are likely to go through heavy changes due to a will in increasing the boat traffic and to the effects of climate change. Those changes would lead to a greater need of an automatic and intelligent planning for an adaptive and resilient water management. A representative model of the network is proposed and tested using MDPs with promising results on the water management optimization. The proposed model permits to coordinate multiple entities over multiple time steps in order to avoid a flood and drought, in the waterway network. However, the proposed model suffers a lack of scalability and is unable to represent a real case application. The advantages and limitations of several approaches of the literature are discussed according to our case study.Les réseaux de voies navigables devraient subir des changements importants en raison d'une volonté d'augmenter le trafic naval et des effets du changement climatique. Ces changements nécessitent une gestion adaptative et résiliente de la ressource en eau et requièrent donc une planification plus intelligente. Un modèle représentatif du réseau, utilisant des MDPs, est proposé et testé afin d'optimiser la gestion de l'eau. Il fournit des résultats prometteurs, le modèle proposé permet de coordonner plusieurs entités sur plusieurs pas de temps de façon à éviter les inondations et sécheresses dans le réseau. Cependant, la solution proposée ne permet pas de passer à l'échelle et n'est pas utilisable dans une application réelle. Les avantages et limitations de plusieurs approches de la littérature qui pourrait permettre de passer à l'échelle sont présentés et discutés sous le prisme de notre étude de cas

Vers une distribution des MDP à grande échelle : étude de cas des voies navigables

National audienceInland waterways networks management methods should undergo significant changes due to a commitment to increase the waterway traffic in a context of climate change. These new constraints will impose an adaptive and resilient management of the water resource leading to an optimal planning of its distribution over the integrity of the inland waterway network, while taking into account the uncertainties arising from their operation. A MDP based approach is proposed to address this problem. It allows the coordination of multiple entities over multiple time steps. Its use on a subnetwork of the waterway made from 2 reaches leads to a minimization of the impacts of flood and drought periods. Despite promising results, the scaling mechanisms for considering a real application are not fully defined. Different approaches proposed in the literature for scaling are discussed by identifying their advantages and limitations. Among them, a distributed modeling is privileged and a new resolution algorithm is proposed. It is tested on a subnetwork composed of 7 reaches.La gestion des réseaux de voies navigables devrait subir des modifications notables en raison d'une volonté d'accroître le trafic fluvial dans un contexte de changement climatique.Ces nouvelles contraintes vont imposer une gestion adaptative et résiliente de la ressource en eau conduisant à une planification de sa répartition sur l'ensemble de ces réseaux.Une approche basée sur les MDP est proposée afin de répondre à cette problématique.Elle permet la coordination de plusieurs entités sur plusieurs pas de temps.Son utilisation sur un sous-réseau de voies navigables conduit à une minimisation de l'impact négatif lors d'événements de montées des eaux ou de sécheresse.Malgré des premiers résultats prometteurs, les mécanismes de passage à l'échelle permettant de considérer une application réelle ne sont pas totalement définis. Différentes approches proposées dans la littérature pour le passage à l'échelle sont discutées en dégageant leurs avantages et limitations.Parmi elles, une modélisation distribuée est privilégiée et un nouvel algorithme de résolution est proposé.Il est testé sur un sous-réseau de 7 biefs