121 research outputs found
Algorithms for Rapidly Dispersing Robot Swarms in Unknown Environments
We develop and analyze algorithms for dispersing a swarm of primitive robots
in an unknown environment, R. The primary objective is to minimize the
makespan, that is, the time to fill the entire region. An environment is
composed of pixels that form a connected subset of the integer grid.
There is at most one robot per pixel and robots move horizontally or
vertically at unit speed. Robots enter R by means of k>=1 door pixels
Robots are primitive finite automata, only having local communication, local
sensors, and a constant-sized memory.
We first give algorithms for the single-door case (i.e., k=1), analyzing the
algorithms both theoretically and experimentally. We prove that our algorithms
have optimal makespan 2A-1, where A is the area of R.
We next give an algorithm for the multi-door case (k>1), based on a
wall-following version of the leader-follower strategy. We prove that our
strategy is O(log(k+1))-competitive, and that this bound is tight for our
strategy and other related strategies.Comment: 17 pages, 4 figures, Latex, to appear in Workshop on Algorithmic
Foundations of Robotics, 200
Exploration via Structured Triangulation by a Multi-Robot System with Bearing-Only Low-Resolution Sensors
This paper presents a distributed approach for exploring and triangulating an
unknown region using a multi- robot system. The objective is to produce a
covering of an unknown workspace by a fixed number of robots such that the
covered region is maximized, solving the Maximum Area Triangulation Problem
(MATP). The resulting triangulation is a physical data structure that is a
compact representation of the workspace; it contains distributed knowledge of
each triangle, adjacent triangles, and the dual graph of the workspace.
Algorithms can store information in this physical data structure, such as a
routing table for robot navigation Our algorithm builds a triangulation in a
closed environment, starting from a single location. It provides coverage with
a breadth-first search pattern and completeness guarantees. We show the
computational and communication requirements to build and maintain the
triangulation and its dual graph are small. Finally, we present a physical
navigation algorithm that uses the dual graph, and show that the resulting path
lengths are within a constant factor of the shortest-path Euclidean distance.
We validate our theoretical results with experiments on triangulating a region
with a system of low-cost robots. Analysis of the resulting quality of the
triangulation shows that most of the triangles are of high quality, and cover a
large area. Implementation of the triangulation, dual graph, and navigation all
use communication messages of fixed size, and are a practical solution for
large populations of low-cost robots.Comment: 8 pages, 11 figures. To appear in ICRA 201
Controlling Swarms of Robots Using Interpolated Implicit Functions
We address the synthesis of controllers for large groups of robots and sensors, tackling the specific problem of controlling a swarm of robots to generate patterns specified by implicit functions of the form s(x, y) = 0. We derive decentralized controllers that allow the robots to converge to a given curve S and spread along this curve. We consider implicit functions that are weighted sums of radial basis functions created by interpolating from a set of constraint points, which give us a high degree of control over the desired 2D curves. We describe the generation of simple plans for swarms of robots using these functions and illustrate
Trading Safety Versus Performance: Rapid Deployment of Robotic Swarms with Robust Performance Constraints
In this paper we consider a stochastic deployment problem, where a robotic
swarm is tasked with the objective of positioning at least one robot at each of
a set of pre-assigned targets while meeting a temporal deadline. Travel times
and failure rates are stochastic but related, inasmuch as failure rates
increase with speed. To maximize chances of success while meeting the deadline,
a control strategy has therefore to balance safety and performance. Our
approach is to cast the problem within the theory of constrained Markov
Decision Processes, whereby we seek to compute policies that maximize the
probability of successful deployment while ensuring that the expected duration
of the task is bounded by a given deadline. To account for uncertainties in the
problem parameters, we consider a robust formulation and we propose efficient
solution algorithms, which are of independent interest. Numerical experiments
confirming our theoretical results are presented and discussed
Stigmergy-based, Dual-Layer Coverage of Unknown Indoor Regions
We present algorithms for uniformly covering an unknown indoor region with a
swarm of simple, anonymous and autonomous mobile agents. The exploration of
such regions is made difficult by the lack of a common global reference frame,
severe degradation of radio-frequency communication, and numerous ground
obstacles. We propose addressing these challenges by using airborne agents,
such as Micro Air Vehicles, in dual capacity, both as mobile explorers and
(once they land) as beacons that help other agents navigate the region.
The algorithms we propose are designed for a swarm of simple, identical,
ant-like agents with local sensing capabilities. The agents enter the region,
which is discretized as a graph, over time from one or more entry points and
are tasked with occupying all of its vertices. Unlike many works in this area,
we consider the requirement of informing an outside operator with limited
information that the coverage mission is complete. Even with this additional
requirement we show, both through simulations and mathematical proofs, that the
dual role concept results in linear-time termination, while also besting many
well-known algorithms in the literature in terms of energy use
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