3,980 research outputs found
Optimal byzantine resilient convergence in oblivious robot networks
Given a set of robots with arbitrary initial location and no agreement on a
global coordinate system, convergence requires that all robots asymptotically
approach the exact same, but unknown beforehand, location. Robots are
oblivious-- they do not recall the past computations -- and are allowed to move
in a one-dimensional space. Additionally, robots cannot communicate directly,
instead they obtain system related information only via visual sensors. We draw
a connection between the convergence problem in robot networks, and the
distributed \emph{approximate agreement} problem (that requires correct
processes to decide, for some constant , values distance
apart and within the range of initial proposed values). Surprisingly, even
though specifications are similar, the convergence implementation in robot
networks requires specific assumptions about synchrony and Byzantine
resilience. In more details, we prove necessary and sufficient conditions for
the convergence of mobile robots despite a subset of them being Byzantine (i.e.
they can exhibit arbitrary behavior). Additionally, we propose a deterministic
convergence algorithm for robot networks and analyze its correctness and
complexity in various synchrony settings. The proposed algorithm tolerates f
Byzantine robots for (2f+1)-sized robot networks in fully synchronous networks,
(3f+1)-sized in semi-synchronous networks. These bounds are optimal for the
class of cautious algorithms, which guarantee that correct robots always move
inside the range of positions of the correct robots
Getting Close Without Touching: Near-Gathering for Autonomous Mobile Robots
In this paper we study the Near-Gathering problem for a finite set of
dimensionless, deterministic, asynchronous, anonymous, oblivious and autonomous
mobile robots with limited visibility moving in the Euclidean plane in
Look-Compute-Move (LCM) cycles. In this problem, the robots have to get close
enough to each other, so that every robot can see all the others, without
touching (i.e., colliding with) any other robot. The importance of solving the
Near-Gathering problem is that it makes it possible to overcome the restriction
of having robots with limited visibility. Hence it allows to exploit all the
studies (the majority, actually) done on this topic in the unlimited visibility
setting. Indeed, after the robots get close enough to each other, they are able
to see all the robots in the system, a scenario that is similar to the one
where the robots have unlimited visibility.
We present the first (deterministic) algorithm for the Near-Gathering
problem, to the best of our knowledge, which allows a set of autonomous mobile
robots to nearly gather within finite time without ever colliding. Our
algorithm assumes some reasonable conditions on the input configuration (the
Near-Gathering problem is easily seen to be unsolvable in general). Further,
all the robots are assumed to have a compass (hence they agree on the "North"
direction), but they do not necessarily have the same handedness (hence they
may disagree on the clockwise direction).
We also show how the robots can detect termination, i.e., detect when the
Near-Gathering problem has been solved. This is crucial when the robots have to
perform a generic task after having nearly gathered. We show that termination
detection can be obtained even if the total number of robots is unknown to the
robots themselves (i.e., it is not a parameter of the algorithm), and robots
have no way to explicitly communicate.Comment: 25 pages, 8 fiugre
Adoption of vehicular ad hoc networking protocols by networked robots
This paper focuses on the utilization of wireless networking in the robotics domain. Many researchers have already equipped their robots with wireless communication capabilities, stimulated by the observation that multi-robot systems tend to have several advantages over their single-robot counterparts. Typically, this integration of wireless communication is tackled in a quite pragmatic manner, only a few authors presented novel Robotic Ad Hoc Network (RANET) protocols that were designed specifically with robotic use cases in mind. This is in sharp contrast with the domain of vehicular ad hoc networks (VANET). This observation is the starting point of this paper. If the results of previous efforts focusing on VANET protocols could be reused in the RANET domain, this could lead to rapid progress in the field of networked robots. To investigate this possibility, this paper provides a thorough overview of the related work in the domain of robotic and vehicular ad hoc networks. Based on this information, an exhaustive list of requirements is defined for both types. It is concluded that the most significant difference lies in the fact that VANET protocols are oriented towards low throughput messaging, while RANET protocols have to support high throughput media streaming as well. Although not always with equal importance, all other defined requirements are valid for both protocols. This leads to the conclusion that cross-fertilization between them is an appealing approach for future RANET research. To support such developments, this paper concludes with the definition of an appropriate working plan
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