workshop notes
Morten
Breivik and Vegard E. Hovstein
Centre
for Ships and Ocean Structures, Department of Engineering Cybernetics
Norwegian University
of Science and Technology, Trondheim, Norway
[Slides]
Formation Control for Unmanned Surface
Vehicles: Theory and Practice
This talk considers the subject of formation control for unmanned
surface vehicles (USVs) in a leader-follower framework. Specifically,
the talk is divided into two main parts: motion control for single USVs
and motion control for multiple USVs. In the first part, we start by
considering factors that motivate the use of USVs, their historical
development, and the present state of the art for commercial, naval,
and scientific applications. We subsequently elaborate on important
legal issues that concern the use of unmanned vehicle technology. Then
we talk about general motion control issues for marine surface vessels,
as well as specific issues pertaining to USVs. We continue by
introducing a novel motion control design methodology for single USVs,
and end the first part by presenting related simulation and
experimental results. In the second part, we start by discussing
different formation control frameworks, and motivate our choice of
framework by commercial offshore applications. Subsequently, we
evaluate practical aspects associated with leader-follower formation
control for USVs, and end the second part by presenting related
simulation and experimental results. Finally, we consider further work
and future challenges related to formation control for USVs in general.
A.
Aguiar(1), A. Pascoal(1), I. Kaminer(2),
N. Hovakimyan(3)
(1) Institute for
Systems and Robotics, IST, Lisbon, Portugal
(2) Naval
Postgraduate School, Monterey, California, USA
(3) Aerospace &
Ocean Engineering, Virginia Polytechnic Institute & State
University, Blacksburg, VA, USA
[Slides1] [Slides2]
Coordinated Path Following of Multiple UAVs for Time-Critical Missions
in the Presence of Time-Varying Communication Topologies
We address the problem of steering multiple unmanned air vehicles
(UAVs) along given paths (path-following) while meeting desired
temporal coordination constraints, e.g., the vehicles should arrive at
their final destinations at exactly the same time. Path-following
relies on the augmentation of existing autopilots with L1 adaptive
output feedback control laws to obtain inner-outer loop control
structures with guaranteed performance. Multiple vehicle time-critical
coordination is achieved by enforcing temporal constraints on the speed
profiles of the vehicles along their paths in response to information
exchanged over a dynamic communication network. We consider that each
vehicle transmits its coordination state to only a subset of the other
vehicles, as determined by the communications topology adopted. We
address explicitly the case where the communication graph that captures
the underlying communication network topology may be disconnected
during some interval of time or may even fail to be connected at any
instant of time and provide conditions under which the closed-loop
system is stable. Flight test results obtained at Camp Roberts, CA in
2007 demonstrate the benefits of the algorithms developed.
Wei Ren
Department of
Electrical and Computer Engineering, Utah State University, USA
[Slides]
Distributed Multi-vehicle Cooperative
Control: A Consensus Perspective
While autonomous vehicles that perform solo missions can yield
significant benefits, greater efficiency and operational capability
will be realized from teams of autonomous vehicles operating in a
coordinated fashion. Potential applications for multiple autonomous
vehicles include autonomous household appliances, hazardous material
handling systems, distributed reconfigurable sensor networks,
surveillance and reconnaissance, space-based interferometry, and future
autonomous combat systems. To enable these applications, a variety of
cooperative control capabilities need to be developed. These
capabilities include formation control, rendezvous, attitude alignment,
flocking, foraging, task and role assignment, payload transport, air
traffic control, and cooperative search. Execution of these
capabilities requires that individual vehicles share a consistent view
of the objectives and the world. Information consensus guarantees that
vehicles sharing information over a network topology have a consistent
view of information that is critical to the coordination task. By
necessity, consensus algorithms are designed to be distributed,
assuming only neighbor-to-neighbor interaction between vehicles.
Consensus algorithms have applications in rendezvous, formation
control, flocking, attitude alignment, and sensor networks. The purpose
of this talk is to overview recent research in distributed consensus
algorithms and their applications in multi-vehicle cooperative control.
Theoretical results on distributed consensus algorithms where the
dynamics of the information state evolve according to first- and
second-order dynamics and according to rigid body attitude dynamics and
Euler-Lagrange equations will be introduced. Application examples of
the distributed consensus algorithms in multi-vehicle cooperative
control including rendezvous and formation keeping for wheeled mobile
robots, UAV formation flying, deep space spacecraft attitude alignment,
and synchronization of networked Euler-Lagrange systems will also be
introduced.
Alain
Sarlette and Rudolphe Sepulchre
Department of
Electrical Engineering and Computer Science, B28
Université de Liège
B-4000 Liege Sart-Tilman, Belgium
[Slides]
Design of stable collective motions on
manifolds
The design and analysis of collective behavior of multiple agents,
resulting from their individual control laws and interactions among
them, has recently attracted much attention. Motivating applications
include formation control of unmanned aerial vehicles (UAVs) and
spacecraft, cooperative robotics, and sensor networks e.g. for ocean
sampling.
The present talk focuses on the geometric aspects of collective motion.
It starts by observing how nonlinear manifolds appear naturally in many
relevant applications. Then several issues concerning agreement
("consensus") on manifolds are briefly discussed. Finally, a method is
presented for the design of control laws that achieve general
collective motions on Lie groups. The theoretical concepts are
illustrated on a simple model of moving rigid bodies in the plane.
The talk reports on joint work with Naomi Leonard and Derek Paley at
Princeton University, Luca Scardovi at University of Liege / Princeton
University and Silvere Bonnabel at University of Liege.
Nuno
Martins
University of
Maryland College Park
Department of Electrical and Computer Engineering
Institute for Systems Research
University of Maryland, College Park, MD 20740 USA
[Slides]
Optimal Design of Formations for
Wireless Networks of Mobile and Static Agents
In this talk, we introduce a new optimization paradigm which aims at
the joint design of the power allocation and of the placement of agents
forming a wireless network. We consider a large class of cost
functions, such as the total power used by all agents, or the network's
maximum power per agent. In addition, we consider network-centric
constraints, with important applications to networked control and
sensor networks. Our model of the wireless medium is well adapted to
high absorption media, such as radio frequency sub sea networks. We
show that our optimization problem can be solved, with arbitrary
accuracy, via geometric programming techniques. We also provide
examples where the optimal solution can be found dynamically via a
distributed algorithm.