1,171 research outputs found
Controlling rigid formations of mobile agents under inconsistent measurements
Despite the great success of using gradient-based controllers to stabilize
rigid formations of autonomous agents in the past years, surprising yet
intriguing undesirable collective motions have been reported recently when
inconsistent measurements are used in the agents' local controllers. To make
the existing gradient control robust against such measurement inconsistency, we
exploit local estimators following the well known internal model principle for
robust output regulation control. The new estimator-based gradient control is
still distributed in nature and can be constructed systematically even when the
number of agents in a rigid formation grows. We prove rigorously that the
proposed control is able to guarantee exponential convergence and then
demonstrate through robotic experiments and computer simulations that the
reported inconsistency-induced orbits of collective movements are effectively
eliminated.Comment: 10 page
Distributed scaling control of rigid formations
Recently it has been reported that biased range-measurements among
neighboring agents in the gradient distance-based formation control can lead to
predictable collective motion. In this paper we take advantage of this effect
and by introducing distributed parameters to the prescribed inter-distances we
are able to manipulate the steady-state motion of the formation. This
manipulation is in the form of inducing simultaneously the combination of
constant translational and angular velocities and a controlled scaling of the
rigid formation. While the computation of the distributed parameters for the
translational and angular velocities is based on the well-known graph rigidity
theory, the parameters responsible for the scaling are based on some recent
findings in bearing rigidity theory. We carry out the stability analysis of the
modified gradient system and simulations in order to validate the main result.Comment: 6 pages In proceedings 55th Conference on Decision and Control, year
201
Distributed stabilization control of rigid formations with prescribed orientation
Most rigid formation controllers reported in the literature aim to only
stabilize a rigid formation shape, while the formation orientation is not
controlled. This paper studies the problem of controlling rigid formations with
prescribed orientations in both 2-D and 3-D spaces. The proposed controllers
involve the commonly-used gradient descent control for shape stabilization, and
an additional term to control the directions of certain relative position
vectors associated with certain chosen agents. In this control framework, we
show the minimal number of agents which should have knowledge of a global
coordinate system (2 agents for a 2-D rigid formation and 3 agents for a 3-D
rigid formation), while all other agents do not require any global coordinate
knowledge or any coordinate frame alignment to implement the proposed control.
The exponential convergence to the desired rigid shape and formation
orientation is also proved. Typical simulation examples are shown to support
the analysis and performance of the proposed formation controllers.Comment: This paper was submitted to Automatica for publication. Compared to
the submitted version, this arXiv version contains complete proofs, examples
and remarks (some of them are removed in the submitted version due to space
limit.
Controlling a triangular flexible formation of autonomous agents
In formation control, triangular formations consisting of three autonomous
agents serve as a class of benchmarks that can be used to test and compare the
performances of different controllers. We present an algorithm that combines
the advantages of both position- and distance-based gradient descent control
laws. For example, only two pairs of neighboring agents need to be controlled,
agents can work in their own local frame of coordinates and the orientation of
the formation with respect to a global frame of coordinates is not prescribed.
We first present a novel technique based on adding artificial biases to
neighboring agents' range sensors such that their eventual positions correspond
to a collinear configuration. Right after, a small modification in the bias
terms by introducing a prescribed rotation matrix will allow the control of the
bearing of the neighboring agents.Comment: 7 pages, accepted in the 20th World Congress of the International
Federation of Automatic Control (IFAC
Taming mismatches in inter-agent distances for the formation-motion control of second-order agents
This paper presents the analysis on the influence of distance mismatches on
the standard gradient-based rigid formation control for second-order agents. It
is shown that, similar to the first-order case as recently discussed in the
literature, these mismatches introduce two undesired group behaviors: a
distorted final shape and a steady-state motion of the group formation. We show
that such undesired behaviors can be eliminated by combining the standard
formation control law with distributed estimators. Finally, we show how the
mismatches can be effectively employed as design parameters in order to control
a combined translational and rotational motion of the formation.Comment: 14 pages, conditionally accepted in Automatic Control, IEEE
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