29,921 research outputs found
Optimal Dynamic Formation Control of Multi-Agent Systems in Environments with Obstacles
We address the optimal dynamic formation problem in mobile leader-follower
networks where an optimal formation is generated to maximize a given objective
function while continuously preserving connectivity. We show that in a convex
mission space, the connectivity constraints can be satisfied by any feasible
solution to a mixed integer nonlinear optimization problem. When the optimal
formation objective is to maximize coverage in a mission space cluttered with
obstacles, we separate the process into intervals with no obstacles detected
and intervals where one or more obstacles are detected. In the latter case, we
propose a minimum-effort reconfiguration approach for the formation which still
optimizes the objective function while avoiding the obstacles and ensuring
connectivity. We include simulation results illustrating this dynamic formation
process
Decentralized Ergodic Control: Distribution-Driven Sensing and Exploration for Multi-Agent Systems
We present a decentralized ergodic control policy for time-varying area
coverage problems for multiple agents with nonlinear dynamics. Ergodic control
allows us to specify distributions as objectives for area coverage problems for
nonlinear robotic systems as a closed-form controller. We derive a variation to
the ergodic control policy that can be used with consensus to enable a fully
decentralized multi-agent control policy. Examples are presented to illustrate
the applicability of our method for multi-agent terrain mapping as well as
target localization. An analysis on ergodic policies as a Nash equilibrium is
provided for game theoretic applications.Comment: 8 pages, Accepted for publication in IEEE Robotics and Automation
Letter
A Survey on Open Problems for Mobile Robots
Gathering mobile robots is a widely studied problem in robotic research. This
survey first introduces the related work, summarizing models and results. Then,
the focus shifts on the open problem of gathering fat robots. In this context,
"fat" means that the robot is not represented by a point in a bidimensional
space, but it has an extent. Moreover, it can be opaque in the sense that other
robots cannot "see through" it. All these issues lead to a redefinition of the
original problem and an extension of the CORDA model. For at most 4 robots an
algorithm is provided in the literature, but is gathering always possible for
n>4 fat robots? Another open problem is considered: Boundary Patrolling by
mobile robots. A set of mobile robots with constraints only on speed and
visibility is working in a polygonal environment having boundary and possibly
obstacles. The robots have to perform a perpetual movement (possibly within the
environment) so that the maximum timespan in which a point of the boundary is
not being watched by any robot is minimized.Comment: 28 pages, 4 figure
Deployment of mobile routers ensuring coverage and connectivity
Maintaining connectivity among a group of autonomous agents exploring an area
is very important, as it promotes cooperation between the agents and also helps
message exchanges which are very critical for their mission. Creating an
underlying Ad-hoc Mobile Router Network (AMRoNet) using simple robotic routers
is an approach that facilitates communication between the agents without
restricting their movements. We address the following question in our paper:
How to create an AMRoNet with local information and with minimum number of
routers? We propose two new localized and distributed algorithms 1)
agent-assisted router deployment and 2) a self-spreading for creating AMRoNet.
The algorithms use a greedy deployment strategy for deploying routers
effectively into the area maximizing coverage and a triangular deployment
strategy to connect different connected component of routers from different
base stations. Empirical analysis shows that the proposed algorithms are the
two best localized approaches to create AMRoNets.Comment: International Journal of Computer Networks & Communications (IJCNC
Multi-robot motion planning via optimal transport theory
In this work we establish a simple yet effective strategy, based on optimal
transport theory, for enabling a group of robots to accomplish complex tasks,
such as shape formation and assembly. We demonstrate the feasibility of this
approach and rigorously prove collision avoidance and convergence properties of
the proposed algorithms
Local Interactions for Cohesive Flexible Swarms
Distributed gathering algorithms aim to achieve complete visibility graphs
via a "never lose a neighbour" policy. We suggest a method to maintain
connected graph topologies, while reducing the number of effective edges in the
graph to order n. This allows to achieve different goals and swarming
behaviours: the system remains connected but flexible, hence can maneuver in
environments that are replete with obstacles and narrow passages, etc
Distributed Communication-aware Motion Planning for Multi-agent Systems from STL and SpaTeL Specifications
In future intelligent transportation systems, networked vehicles coordinate
with each other to achieve safe operations based on an assumption that
communications among vehicles and infrastructure are reliable. Traditional
methods usually deal with the design of control systems and communication
networks in a separated manner. However, control and communication systems are
tightly coupled as the motions of vehicles will affect the overall
communication quality. Hence, we are motivated to study the co-design of both
control and communication systems. In particular, we propose a control
theoretical framework for distributed motion planning for multi-agent systems
which satisfies complex and high-level spatial and temporal specifications
while accounting for communication quality at the same time. Towards this end,
desired motion specifications and communication performances are formulated as
signal temporal logic (STL) and spatial-temporal logic (SpaTeL) formulas,
respectively. The specifications are encoded as constraints on system and
environment state variables of mixed integer linear programs (MILP), and upon
which control strategies satisfying both STL and SpaTeL specifications are
generated for each agent by employing a distributed model predictive control
(MPC) framework. Effectiveness of the proposed framework is validated by a
simulation of distributed communication-aware motion planning for multi-agent
systems.Comment: Submitted for publication on 2017 IEEE Conference on Decision and
Control (CDC2017
Connectivity maintenance by robotic Mobile Ad-hoc NETwork
The problem of maintaining a wireless communication link between a fixed base
station and an autonomous agent by means of a team of mobile robots is
addressed in this work. Such problem can be of interest for search and rescue
missions in post disaster scenario where the autonomous agent can be used for
remote monitoring and first hand knowledge of the aftermath, while the mobile
robots can be used to provide the agent the possibility to dynamically send its
collected information to an external base station. To study the problem, a
distributed multi-robot system with wifi communication capabilities has been
developed and used to implement a Mobile Ad-hoc NETwork (MANET) to guarantee
the required multi-hop communication. None of the robots of the team possess
the knowledge of agent's movement, neither they hold a pre-assigned position in
the ad-hoc network but they adapt with respect to the dynamic environmental
situations. This adaptation only requires the robots to have the knowledge of
their position and the possibility to exchange such information with their
one-hop neighbours. Robots' motion is achieved by implementing a behavioural
control, namely the Null-Space based Behavioural control, embedding the
collective mission to achieve the required self-configuration. Validation of
the approach is performed by means of demanding experimental tests involving
five ground mobile robots capable of self localization and dynamic obstacle
avoidance
Multi-Robot Data Gathering Under Buffer Constraints and Intermittent Communication
We consider a team of heterogeneous robots which are deployed within a common
workspace to gather different types of data. The robots have different roles
due to different capabilities: some gather data from the workspace (source
robots) and others receive data from source robots and upload them to a data
center (relay robots). The data-gathering tasks are specified locally to each
source robot as high-level Linear Temporal Logic (LTL) formulas, that capture
the different types of data that need to be gathered at different regions of
interest. All robots have a limited buffer to store the data. Thus the data
gathered by source robots should be transferred to relay robots before their
buffers overflow, respecting at the same time limited communication range for
all robots. The main contribution of this work is a distributed motion
coordination and intermittent communication scheme that guarantees the
satisfaction of all local tasks, while obeying the above constraints. The robot
motion and inter-robot communication are closely coupled and coordinated during
run time by scheduling intermittent meeting events to facilitate the local plan
execution. We present both numerical simulations and experimental studies to
demonstrate the advantages of the proposed method over existing approaches that
predominantly require all-time network connectivity.Comment: 14 Pages, 16 figure
Distributed Cohesive Control for Robot Swarms: Maintaining Good Connectivity in the Presence of Exterior Forces
We present a number of powerful local mechanisms for maintaining a dynamic
swarm of robots with limited capabilities and information, in the presence of
external forces and permanent node failures. We propose a set of local
continuous algorithms that together produce a generalization of a Euclidean
Steiner tree. At any stage, the resulting overall shape achieves a good
compromise between local thickness, global connectivity, and flexibility to
further continuous motion of the terminals. The resulting swarm behavior scales
well, is robust against node failures, and performs close to the best known
approximation bound for a corresponding centralized static optimization
problem
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