297 research outputs found
Mutual visibility by luminous robots without collisions
We consider the Mutual Visibility problem for anonymous dimensionless robots with obstructed visibility moving in a plane: starting from distinct locations, the robots must reach, without colliding, a configuration where no three of them are collinear. We study this problem in the luminous robots model, in which each robot has a visible light that can assume colors from a fixed set. Among other results, we prove that Mutual Visibility can be solved in SSynch with 2 colors and in ASynch with 3 colors. If an adversary can interrupt and stop a robot moving to its computed destination, Mutual Visibility is still solvable in SSynch with 3 colors and, if the robots agree on the direction of one axis, also in ASynch. As a byproduct, we provide the first obstructed-visibility solutions to two classical problems for oblivious robots: collision-less convergence to a point (also known as near-gathering) and circle formation
Plane Formation by Synchronous Mobile Robots in the Three Dimensional Euclidean Space
Creating a swarm of mobile computing entities frequently called robots,
agents or sensor nodes, with self-organization ability is a contemporary
challenge in distributed computing. Motivated by this, we investigate the plane
formation problem that requires a swarm of robots moving in the three
dimensional Euclidean space to land on a common plane. The robots are fully
synchronous and endowed with visual perception. But they do not have
identifiers, nor access to the global coordinate system, nor any means of
explicit communication with each other. Though there are plenty of results on
the agreement problem for robots in the two dimensional plane, for example, the
point formation problem, the pattern formation problem, and so on, this is the
first result for robots in the three dimensional space. This paper presents a
necessary and sufficient condition for fully-synchronous robots to solve the
plane formation problem that does not depend on obliviousness i.e., the
availability of local memory at robots. An implication of the result is
somewhat counter-intuitive: The robots cannot form a plane from most of the
semi-regular polyhedra, while they can form a plane from every regular
polyhedron (except a regular icosahedron), whose symmetry is usually considered
to be higher than any semi-regular polyhedrdon
Meeting in a Polygon by Anonymous Oblivious Robots
The Meeting problem for searchers in a polygon (possibly with
holes) consists in making the searchers move within , according to a
distributed algorithm, in such a way that at least two of them eventually come
to see each other, regardless of their initial positions. The polygon is
initially unknown to the searchers, and its edges obstruct both movement and
vision. Depending on the shape of , we minimize the number of searchers
for which the Meeting problem is solvable. Specifically, if has a
rotational symmetry of order (where corresponds to no
rotational symmetry), we prove that searchers are sufficient, and
the bound is tight. Furthermore, we give an improved algorithm that optimally
solves the Meeting problem with searchers in all polygons whose
barycenter is not in a hole (which includes the polygons with no holes). Our
algorithms can be implemented in a variety of standard models of mobile robots
operating in Look-Compute-Move cycles. For instance, if the searchers have
memory but are anonymous, asynchronous, and have no agreement on a coordinate
system or a notion of clockwise direction, then our algorithms work even if the
initial memory contents of the searchers are arbitrary and possibly misleading.
Moreover, oblivious searchers can execute our algorithms as well, encoding
information by carefully positioning themselves within the polygon. This code
is computable with basic arithmetic operations, and each searcher can
geometrically construct its own destination point at each cycle using only a
compass. We stress that such memoryless searchers may be located anywhere in
the polygon when the execution begins, and hence the information they initially
encode is arbitrary. Our algorithms use a self-stabilizing map construction
subroutine which is of independent interest.Comment: 37 pages, 9 figure
Circle Formation by Asynchronous Opaque Fat Robots on an Infinite Grid
This study addresses the problem of "Circle Formation on an Infinite Grid by
Fat Robots" (). Unlike prior work focused solely on point robots
in discrete domain, it introduces fat robots to circle formation on an infinite
grid, aligning with practicality as even small robots inherently possess
dimensions. The algorithm, named , resolves the
problem using a swarm of fat luminous robots. Operating under an asynchronous
scheduler, it achieves this with five distinct colors and by leveraging
one-axis agreement among the robots
Sycamore - 2D/3D Mobile Robots simulation environment
The distributed coordination and control of a team of autonomous mobile robots is a problem widely studied in a variety of fields, such as engineering, artificial intelligence, artificial life, robotics. Generally, in these areas, the problem is studied mostly from a practical point of view. Recently, the study of what can be computed by such team of robots has become increasingly popular in theoretical computer science and especially in distributed computing, where it is now an integral part of the investigations on computability by mobile entities. The autonomous mobile robots model imagines the involved entities being capable of moving, observing the environment and computing. This kind of paradigm often produces complex configurations, for which the mathematical proof of correctness can be found more easily with the help of an empirical approach.
This thesis will describe my work on a 2D/3D simulation environment for autonomous mobile robots called Sycamore. The work consisted in the implementation of the simulator and a rich set of plugins for it, followed by the implementation and testing of an algorithm that is solving a problem in the mobile robots theory: "NearGathering". The final part of the work made me design, implement and test a solution for a completely new problem: "Following with directional limited visibility"
On Asynchrony, Memory, and Communication: Separations and Landscapes
Research on distributed computing by a team of identical mobile computational
entities, called robots, operating in a Euclidean space in
-- () cycles, has
recently focused on better understanding how the computational power of robots
depends on the interplay between their internal capabilities (i.e., persistent
memory, communication), captured by the four standard computational models
(OBLOT, LUMI, FSTA, and FCOM) and the conditions imposed by the external
environment, controlling the activation of the robots and their synchronization
of their activities, perceived and modeled as an adversarial scheduler.
We consider a set of adversarial asynchronous schedulers ranging from the
classical semi-synchronous (SSYNCH) and fully asynchronous (ASYNCH) settings,
including schedulers (emerging when studying the atomicity of the combination
of operations in the cycles) whose adversarial power is in
between those two. We ask the question: what is the computational relationship
between a model under adversarial scheduler () and a
model under scheduler ()? For example, are the robots in
more powerful (i.e., they can solve more problems) than those in
?
We answer all these questions by providing, through cross-model analysis, a
complete characterization of the computational relationship between the power
of the four models of robots under the considered asynchronous schedulers. In
this process, we also provide qualified answers to several open questions,
including the outstanding one on the proper dominance of SSYNCH over ASYNCH in
the case of unrestricted visibility
- …