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Optimal Construction of Control Graphs in Multi-Robot Systems

Ilan Lupu. Optimal Construction of Control Graphs in Multi-Robot Systems. Master's Thesis, Bar Ilan University,2015.

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Abstract

Control graphs are used in multi-robot systems to maintain information about which robot senses another robot, and at what position. On the basis of such graphs, it is possible to compute a shared coordinate system, localize relative to others, and maintain stable formations. While existing work shows how to utilize control graphs for these tasks, it makes two critical assumptions. First, it assumes edge weights of control graphs are single deterministic scalars. However in reality there are many stochastic factors (e.g, latency, resource costs, or position errors), that affect optimality of control graphs. Second, it assumes that a single robot is given, to serve as the global anchor for the robots’ relative positioning and location estimates. However, optimal selection of this robot is an open problem. In this work, we generalize control graphs to distinguish different stochastic sensing factors that may be represented by control graphs, beyond existing work, and discuss risk-based policies for their treatment. We show that existing work in coordinate frame alignment and formation maintenance may be recast as graph-theoretic algorithms inducing control graphs for more general representation of the sensing capabilities of robots. We then formulate the problem of optimal selection of an anchor, and present a centralized algorithm for solving it. We evaluate use of these algorithm on physical and simulated robots equipped with depth and image sensors (RGB-D cameras), and show they very significantly improve on existing work.

Additional Information

BibTeX

@MastersThesis{lupu-msc,
author = {Ilan Lupu},
title = {Optimal Construction of Control Graphs in Multi-Robot Systems},
school = {{B}ar {I}lan {U}niversity},
year = {2015},
OPTkey = {},
OPTtype = {},
OPTaddress = {},
OPTmonth = {},
OPTnote = {Available at \url{http://www.cs.biu.ac.il/~galk/Publications/b2hd-lupu-msc.html}},
OPTannote = {},
  wwwnote = {}, 
  abstract = {Control graphs are used in multi-robot systems to maintain information 
  about which robot senses another robot, and at what position. On the basis of such graphs, 
  it is possible to compute a shared coordinate system, localize relative to others, 
  and maintain stable formations. While existing work shows how to utilize control graphs for 
these tasks, it makes two critical assumptions. First, it assumes edge 
weights of control graphs are single deterministic scalars. However in 
reality there are many stochastic factors (e.g, latency, resource costs, 
or position errors), that affect optimality of control graphs. Second, 
it assumes that a single robot is given, to serve as the global anchor 
for the robots’ relative positioning and location estimates. However, 
optimal selection of this robot is an open problem. In this work, we 
generalize control graphs to distinguish different stochastic sensing factors 
that may be represented by control graphs, beyond existing work, 
and discuss risk-based policies for their treatment. We show that existing 
work in coordinate frame alignment and formation maintenance 
may be recast as graph-theoretic algorithms inducing control graphs 
for more general representation of the sensing capabilities of robots. 
We then formulate the problem of optimal selection of an anchor, and 
present a centralized algorithm for solving it. We evaluate use of these 
algorithm on physical and simulated robots equipped with depth and 
image sensors (RGB-D cameras), and show they very significantly improve 
on existing work. },
}

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