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  • FACULTAD DE INFORMTICA UNIVERSIDAD POLITCNICA DE MADRID

    TESIS DE MASTER

    MSTER EN TECNOLOGAS DE LA INFORMACIN

    DISTRIBUTED AWARD PROTOCOL:

    A COOPERATION AND COMMUNICATION METHOD FOR ROBOTS

    AUTOR: KRZYSZTOF KWIATKOWSKI TUTOR: NIK SWOBODA

    JULIO 2013

  • i

    Abstract In this Masters Thesis a new Distributed Award Protocol (DAP) for robot communication and cooperation is presented. Task assignment (contract awarding) is done dynamically with contracts assigned to robots based upon the best bid received. Instead of having a manager and a contractor it is proposed a fully distributed bidding/awarding mechanism without a distinguished master. The best bidding robots are awarded with contract for execution. The contractors make decisions locally. This brings the following benefits: no communication bottleneck, low computational power requirement, increased robustness. DAP can handle multitasking. Tasks can be injected into system during the execution of already allocated tasks. As tasks have priorities, in the next cycle after taking into account actual bid parameters of all robots, tasks can be re-allocated. The aim is to minimize a global cost function which is a compromise between cost of task execution and cost of resources usage. Information about tasks and bid values is spread among robots with the use of a Round Robin Route, which is a novel solution proposed in this work. This method allows also identifying failed robots. Such failed robot is eliminated from the list of awarded robots and its replacement is found so the task is still executed by a team. If the failure of a robot was temporary (e.g. communication noise) and the robot can recover, it can again participate in the next bidding/awarding process. Using a bidding/awarding mechanism allows robots to dynamically relocate among tasks. This is also contributes to system robustness. DAP was evaluated through multiple experiments done in the multi-robot simulation system. Various scenarios were tested to check the idea of the main algorithm. Different failures of robots (communication failures, partial hardware malfunctions) were simulated and observations were made regarding how DAP recovers from them. Also the DAP flexibility to environment changes was watched. The experiments in the simulated environment confirmed the above features of DAP.

  • ii

    Resumen (espaol) En la Tesis Fin de Mster, se presenta un nuevo Distributed Awarded Protocol (DAP) para la comunicacin y la cooperacin entre los robots. La asignacin de tareas (adjudicacin del contrato) se realiza de forma dinmica con los contratos que mejor se adapten a los robots de licitacin/subasta. En lugar de tener un gerente y un contratista se propuesto que haya un mecanismo de adjudicacin sin un lder. A los mejores robots de la subasta se les otorga la ejecucin el contacto. Los contratistas toman las decisiones en nivel local. Esto trae las siguientes ventajas: no hay atascos de comunicacin y el requerimiento de clculo es bajo y se incrementa robustez. DAP puede manejar mltiples tareas. Las tareas pueden ser inyectadas en el sistema durante la ejecucin de otras tareas ya asignados. En el siguiente ciclo, tras tener en cuenta los parmetros de la oferta de los robots, las tareas pueden ser reasignadas. El objetivo es minimizar la funcin de costes globales, un compromiso entre el coste de la ejecucin de las tareas y el coste de los recursos usados. La informacin sobre los valores de la tarea y la oferta se reparte entre los robots con el uso de una ruta de Round Robin que es una solucin novedosa propuesta en este trabajo. Este mtodo permite tambin la identificacin de los robots fallidos. Tales robots no se eliminan de la lista de robots adjudicados y su sustitucin se encuentra, por lo que la tarea an se ejecutada por un equipo. Si el fallo del robot era temporal (por ejemplo, ruido de comunicacin) y el robot puede recuperarlo, despus puede participar en la prxima nueva oferta / proceso de adjudicacin. Usar una oferta / mecanismo de adjudicacin permite a los robots reubicarse dinmicamente entre las tareas. Esta es tambin la contribucin a la robustez del sistema. DAP se evalu a travs de mltiples experimentos realizados en el sistema de simulacin de mltiples robots. Varios escenarios se analizaron para comprobar la idea del algoritmo principal. Se simularon diferentes fallos de robots (fallas en la comunicacin, fallos de hardware parcial) y las observaciones se realizaron viendo cmo DAP se recupera de ellos. Tambin se observ la flexibilidad DAP a los cambios del entorno. Los experimentos en el entorno simulado confirmaron esas caractersticas de DAP.

  • iii

    Table of content 1 Introduction ............................................................................................................... 1 2 Related work .............................................................................................................. 2 3 Constraints and assumptions ....................................................................................... 9 4 Distributed Award Protocol description ......................................................................... 10

    4.1 Single task .........................................................................................................10 4.2 Multi-task allocation ............................................................................................15 4.3 DAP context .......................................................................................................19

    4.3.1 Task_Table description ..................................................................................19 4.3.2 Bid_Table description .....................................................................................20

    4.4 Exceptions to Protocol flow ..................................................................................21 4.4.1 Communication failures ..................................................................................21 4.4.2 Hardware malfunction failures ........................................................................24 4.4.3 Dealing with exceptions .................................................................................25

    5 DAP example of implementation ............................................................................... 26 5.1 Assumptions of an experiment .............................................................................26 5.2 Bid specification example ....................................................................................26 5.3 Simulated environment .......................................................................................27 5.4 Algorithm steps ..................................................................................................29 5.5 Dynamic environment .........................................................................................36

    6 Evaluation ................................................................................................................. 37 7 Conclusions and future works ..................................................................................... 44 8 Glossary .................................................................................................................... 48 Bibliography ..................................................................................................................... 49

  • iv

    Table of figures Figure 1: FIPA Contract Net Interaction Protocol ................................................................................... 5 Figure 2: DAP timing ........................................................................................................................... 9 Figure 3 Single task in DAP ............................................................................................................... 13 Figure 4: DAP in the time domain ...................................................................................................... 14 Figure 5: Bid_Table sorting code ................................................................................................... 16

    Figure 6: Multi-task allocation in DAP ................................................................................................. 17 Figure 7: Communication failure during the Return Round Robin Route ................................................ 23 Figure 8: DAP simulator environment ................................................................................................. 27 Figure 9: Robot design ...................................................................................................................... 28 Figure 10: Task design ...................................................................................................................... 28 Figure 11: First Round Robin Route step 1 .......................................................................................... 29 Figure 12: First Round Robin Route next steps.................................................................................... 30 Figure 13: First Round Robin Route last step ...................................................................................... 31 Figure 14: Return Round Robin Route ................................................................................................ 31 Figure 15: Robots allocated to the task .............................................................................................. 32 Figure 16: Robots accomplished a task ............................................................................................... 32 Figure 17: Round Robin Route for 3 tasks .......................................................................................... 34 Figure 18: Robots