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Area coverage and communication are fundamental concerns in networks of cooperating robots. The goal is to address the issue of how well a group of collaborating robots having a limited communication range is able to monitor a given geographical space. Typically, an area of interest is partitioned into smaller subareas, with each robot in charge of a given subarea. This gives rise to a communication network that allows robots to exchange information when they are sufficiently close to each other. To be effective, the system must be resilient, i.e., be able to recover from robot failures. In a recent paper Bereg et al. (J Comb Optim 36(2):365–391, 2018), the concept of k-resilience of a synchronized system was introduced as the cardinality of a smallest set of robots whose failure suffices to cause that at least k surviving robots operate without communication, thus entering a state of starvation. It was proven that the problem of computing the k-resilience is NP-hard in general. In this paper, we study several problems related to the resilience of a synchronized system with respect to coverage and communication on realistic topologies including grid and cycle configurations. The broadcasting resilience is the minimum number of robots whose removal may disconnect the network. The coverage resilience is the minimum number of robots whose removal may result in a non-covered subarea. We prove that the three resilience measures can be efficiently computed for these configurations. [ABSTRACT FROM AUTHOR]

We study an optimization problem that arises in the design of covering strategies for multi-robot systems. Consider a team of n cooperating robots traveling along predetermined closed and disjoint trajectories. Each robot needs to periodically communicate information to nearby robots. At places where two trajectories are within range of each other, a communication link is established, allowing two robots to exchange information, provided they are “synchronized”, i.e., they visit the link at the same time. In this setting a communication graph is defined and a system of robots is called synchronized if every pair of neighbors is synchronized. If one or more robots leave the system, then some trajectories are left unattended. To handle such cases in a synchronized system, when a live robot arrives to a communication link and detects the absence of the neighbor, it shifts to the neighboring trajectory to assume the unattended task. If enough robots leave, it may occur that a live robot enters a state of starvation, failing to permanently meet other robots during flight. To measure the tolerance of the system under this phenomenon we define the k-resilience as the minimum number of robots whose removal may cause k surviving robots to enter a state of starvation. We show that the problem of computing the k-resilience is NP-hard if k is part of the input, even if the communication graph is a tree. We propose algorithms to compute the k-resilience for constant values of k in general communication graphs and show more efficient algorithms for systems whose communication graph is a tree. [ABSTRACT FROM AUTHOR]

This paper addresses a synchronization problem that arises when a team of robots needs to communicate while repeatedly performing assigned tasks in a cooperative scenario. Each robot has a limited communication range and moves along a previously defined closed trajectory. When two robots are close enough, a communication link may be established, allowing the robots to exchange information. The goal is to schedule the motions such that the entire system can be synchronized for maximum information exchange; that is, every pair of neighbors always visit the feasible communication link at the same time. An algorithm for scheduling the team of robots in this scenario is proposed and a robust framework that assures the synchronization of a large team of robots is presented. Simulations, experiments, and computational results demonstrate the applicability of the algorithm. The approach allows the design of fault-tolerant systems that can be used for multiple tasks, such as surveillance, area exploration, and searching for targets in hazardous environments, among others. [ABSTRACT FROM PUBLISHER]