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ABSTRACT: Efficient control schemes are required for effective cooperation of robot teams in a mobile wireless sensor network. If the robots (resources) are also in charge of executing multiple simultaneous missions, then risks of deadlocks due to the presence of shared resources among different missions increase and have to be tackled. Discrete event control with deadlock avoidance has been used in the past for robot team coordination for the case of multi reentrant flowline models with shared resources. In this paper we present an analysis of deadlock avoidance for a generalized case of multi reentrant flow line systems (MRF) called the Free Choice Multi Reentrant Flow Line systems (FMRF). In FMRF, some tasks have multiple resource choices; hence routing decisions have to be made and current results in deadlock avoidance for MRF do not hold. This analysis is based on the so-called Circular Waits (CW) of the resources in the system. For FMRF, the well known notions of Critical Siphons and Critical Subsystems must be generalized and we redefine these objects for such systems. Our second contribution provides a matrix formulation that efficiently computes the objects required for deadlock avoidance in FMRF systems. A MAXWIP dispatching policy is formulated for deadlock avoidance in FMRF systems. According to this policy, deadlock in FMRF is avoided by limiting the work in progress (WIP) in the critical subsystems of each CW. Implemented results of the proposed scheme in a WSN test-bed is presented in the paper.
International Journal of Advanced Robotic Systems 09/2008; · 0.38 Impact Factor
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ABSTRACT: This paper uses a novel discrete-event controller (DEC) for the coordination of cooperating heterogeneous wireless sensor networks (WSNs) containing both unattended ground sensors (UGSs) and mobile sensor robots. The DEC sequences the most suitable tasks for each agent and assigns sensor resources according to the current perception of the environment. A matrix formulation makes this DEC particularly useful for WSN, where missions change and sensor agents may be added or may fail. WSN have peculiarities that complicate their supervisory control. Therefore, this paper introduces several new tools for DEC design and operation, including methods for generating the required supervisory matrices based on mission planning, methods for modifying the matrices in the event of failed nodes, or nodes entering the network, and a novel dynamic priority assignment weighting approach for selecting the most appropriate and useful sensors for a given mission task. The resulting DEC represents a complete dynamical description of the WSN system, which allows a fast programming of deployable WSN, a computer simulation analysis, and an efficient implementation. The DEC is actually implemented on an experimental wireless-sensor-network prototyping system. Both simulation and experimental results are presented to show the effectiveness and versatility of the developed control architecture.
IEEE Transactions on Systems Man and Cybernetics Part B (Cybernetics) 09/2006; 36(4):806-19. · 3.08 Impact Factor
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ABSTRACT: In this chapter we have presented a discrete-event coordination scheme for sensor networks composed of both mobile and stationary nodes. This architecture supports highlevel planning for multiple heterogeneous agents with multiple concurrent goals in dynamic environment. The proposed formulation of the DEC represents a complete dynamical description that allows efficient computer simulation of the WSN prior to implementing a given DE coordination scheme on the actual system. The similarity between simulation and experimental results shows the effectiveness of the DEC for simulation analysis. The obtained results also prove the striking potentialities of the matrix formulation of the DEC, namely: straightforward implementation of missions on the ground of intuitive linguistic descriptions; possibility to tackle adaptability and scalability issues at a centralized level using simple matrix operations; guaranteed performances, since the DEC is a mathematical framework which constraints the behaviour of the single agents in a predictable way. Future research will be devoted to the development of highlevel decision making algorithms for the dynamic updates of the matrices of the DEC, in order to automatically reformulate the missions on-line according to the current topology of the network and the current perception of the environment.
07/2005; , ISBN: 3-86611-038-3
