The European Project GREX: Coordination and Control of ...

The European Project GREX: Coordination and Control of
Cooperating Unmanned Systems
1. Abstract
Jörg Kalwa
ATLAS ELEKTRONIK GmbH
Sebaldsbrücker Heerstraße 235
D 28309 Bremen, Germany
Tel.: +49 421 457-2753
Fax: +49 421 457-2020
Joerg.Kalwa@atlas-elektronik.com
Today, scientific and military users demand systems composed of multiple underwater
vehicles, whereby each vehicle plays the role of a sophisticated node (with sensor,
processing, and communication capabilities) in a network – this means combining the
properties of heterogeneous systems in a team.
“Grex” - the Latin word for a herd or flock - indicates the focus of a European research
project, which started in June 2006. The major goal is the creation of a conceptual
framework and middleware to coordinate a flock of heterogeneous unmanned marine
vehicles in order to achieve their mission goal in an optimised manner.
This paper gives an overview about the ambitious goals of the project, which cover
methods from effective mission programming, coordinated mission control and navigation
to ad hoc formation of sensor-networks. It will also show the potential military application
of such a system.
2. Introduction
Currently the exploitation of Unmanned Underwater Vehicles (UUVs) is under rapid development.
One shot mine disposal vehicles are becoming standard, first Autonomous
Underwater Vehicles (AUVs) are introduced for remote sensing as e. g. exploratory/reconnaissance
operations to name a few examples. Modern concepts of naval
mine warfare introduce ships with a variety of different UUVs which might be deployed to
the same time. To summarize the resulting requirements: the management of a group of
heterogeneous vehicles will be essential for the future mine warfare theatre.
Similar needs come from the civil community: offshore geologists, marine researchers or
underwater archaeologists could benefit from the use of multiple vehicles. Each vehicle
may play a different role during the progress of a mission. They form specific nodes in a
network with its own sensors, processing, and communication capabilities, thus combining
the properties of heterogeneous systems into a more capable team. For example:
vehicles intended for searching operations could re-direct vehicles equipped with ma-
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nipulators to extend their scope of activity to rescuing missions. Some systems could
watch other systems at work to record the operations using video or they could serve as
navigation aids or communication relay stations. Multiple vehicles allow surveying wider
areas in less time, simultaneously obtaining time and space resolutions that are otherwise
unachievable. Combining pre-existing vehicles into a team will make research more
effective and will lead to completely new applications.
To coordinate and handle such groups of vehicles the research project GREX has been
created within the 6 th framework of the European Commission. The 3 years project
started in June 2006 and will end in June 2009.
The main goal of the project is to achieve a first level of distributed “intelligence” through
dependable embedded systems that are interconnected and cooperate towards the coordinated
execution of tasks. Thus the project will witness the development of theoretical
methods and practical tools for multiple vehicle cooperation, bridging the gap between
concept and practice. The technology developed must be on one hand sufficiently generic
in order to interface pre-existing heterogeneous systems. On the other hand it must
be sufficiently robust to cover problems caused by faulty communications.
Practically, developments will cover methods for effective programming of multiple systems,
coordinated mission control and navigation, formal methods for validation and testing
of the programming language, and the use of perception and communication techniques
to enable ad hoc formation of information- and sensor-networks. A series of field
trials will be carried out to assess the efficacy of the methods developed. They conclude
and demonstrate the success of the GREX project.
3. Mission Scenarios
The objectives of the GREX project are well rooted in an in-depth analysis of potential
user requirements. There are three types of mission scenarios which are the basis for
discussion and specifications. These mission scenarios envisioned take into account
challenging problems in the field of marine science. They also bring out the ever increasing
important role that marine technology is having in terms of affording marine scientist
the tools that are needed to explore and exploit the ocean. We place the focus on missions
for which the following basic ingredients are required:
• The missions require the use of several “intelligent” autonomous vehicles
equipped with appropriate instrumentation.
• The inter-vehicle coordination and mission control is dynamic and highly dependent
on the type of information obtained as the missions unfold.
The mission can be extended into various related tasks as can be found e. g. in military
missions.
Three typical scenarios are described in detail on the following pages.
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Scenario 1 – the quest for hydrothermal vents
Marine scientists (including geologists and biologists) have by now gathered considerable
knowledge about deep water hydrothermal vents and their intriguing ecosystems
and chemosynthetic life forms. The vents hold considerable potential for the biotechnological
industry and are a window on the evolution of life on planet Earth. They are also
spectacular and generate widespread public interest.
Besides the well known deepwater vents there are strong indications that hydrothermal
vents exist at 150 m depth, around the D. João de Castro Bank [1], but this has not been
proved yet. There is a need worldwide to develop efficient methodologies to detect intermediate
depth vents because of their far reaching implication in the study of the biological
responses to an environment wedged between deep and shallow waters.
Fig. 1: Scenario drawing: the quest for hydrothermal vents
The mission proposed is based on the knowledge that vents produce methane and that
methane does not dissolve quickly in the water. This in turn allows for its detection and
for the measurement of the gradient of its concentration using methane sensors. The
two step mission starts with a fast survey of a given area using a fleet of AUVs equipped
with acoustic sensors. The map produced will allow for the examination of geological
features (acting as indicators of the possible presence of vents) that will guide the choice
of smaller inspection areas. Once a smaller area is found, a fleet of vehicles equipped
with methane sensors can be deployed, as depicted. The vehicle baseline configuration
is such that spatial estimates of the gradient of the methane concentration can be com-
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puted cooperatively. It is up to the fleet to manoeuvre so as to seek the region of higher
concentration, and thus the localisation of the vent.
The scenario described requires multiple vehicle motion coordination based on the type
of information (methane concentration) that is acquired as the mission progresses. The
mission poses formidable challenges to systems designers due to the need to develop a
distributed, multi-vehicle coordination scheme (requiring robust vehicle localization,
navigation, and control) in the presence of stringent underwater communication constraints.
This task is closely related to applications in anti terror warfare, where a team of vehicles
shall locate under water explosives attached to a ship-hull or detect under water penetration
of harbour areas.
Scenario 2 – download data from tagged fish
One of the project partners is involved in a project that uses passive and active telemetry
devices on fishes. These tags are able to log environmental data and to send acoustic
signals which allow tracking of the marked fish. The studies have significantly improved
the understanding of fundamental phenomena such as the dispersal, spawning dynamics
or thermoregulatory mechanisms of marine animals, but most importantly they are
opening a new window in the framework of the spatial management of marine living resources.
Critical impacts include the use of spatial behaviour in fisheries stock assessment
and the design of Marine Protected Areas.
Field experience proved to be difficult to get the data back from the tagged fish. A swam
of AUVs in cooperation with one or more surface crafts would be able to perform a
search task to locate a tagged fish. Two or more autonomous surface vehicles (ASVs)
move in the same direction, while keeping a desired formation pattern (e.g. side by side).
Equipped with acoustic receivers, they sweep the water column as they move along and
listen to the sounds emitted by the acoustic tags. By using more than one ASV, the position
of the tags can be determined with adequate precision.
Upon detecting one or more tags, one of the ASVs communicates to a group of AUVs
the positions of those tags using an acoustic communication network. It is then up to the
AUVs to track the target and stay within the communication range with a given accuracy
(typically, not worse than 100 meters) for a period of time. The period should be sufficient
enough to download the tag data. Upon conclusion of the fish-data download task,
the AUVs manoeuvre back to the vicinity of the steadily moving ASVs, to wait for further
instructions.
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Fig. 2: Scenario drawing: download data from tagged fish
This methodology dispenses with the deployment of fixed underwater units and is specially
suited to scan a given volume of the ocean in a fast and expedite manner. In this
interesting scenario, the AUVs are equipped with acoustic pingers for navigation purposes.
They are further equipped with acoustic modems allowing for direct communications
with the ASVs. We thus have all the ingredients of a complex, albeit powerful network
involving different players, whereby the ASVs play the triple role tag position detectors,
AUV position detectors, and communications relay stations from the AUVs to a
support ship or even to shore. The benefit of such a communication relay is that it can
be deployed and monitored from shore. Underwater experiments can be viewed and/or
controlled by more scientific users than using a ship offshore. Costs can be reduced and
the number or quality of experiments increased.
Scenario 3 - marine habitat mapping
Habitat maps of the marine environment contain data on the bathymetry and nature of
the seabed as well as on the type and localization of biological assemblages. These are
the key to an in-depth understanding of the distribution and extent of marine habitats.
Knowledge of the distribution of marine habitats serves to establish sensible approaches
to the conservation needs of each habitat and to facilitate a better management of the
marine environment. This subject is receiving widespread attention worldwide because
of its far reaching implications and has led to the definition of a number of guidelines and
directives for the study and preservation of marine habitats. At the European level, for
example, Annex I of the celebrated EU Habitats Directive establishes that marine habitats
classified as Special Areas of Conservation need special assessment in order to
verify their accordance with the European Union requirements.
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Fig. 3: Scenario drawing: marine habitat mapping
The scientific mission scenario for marine habitat mapping proposed here was greatly
influenced by and aims to automate and improve “classical” procedures that are normally
used by marine scientists. The key ideas can be explained by referring to figure 3.
For simplicity of exposition, we start by focusing on the ASV/ROV ensemble in the figures,
where the ROV is connected to the ASV through a thin umbilical for fast data
transmission. In this scenario, the ASV executes a lawn mowing manoeuvre above the
seabed automatically, while the ROV executes a similar manoeuvre in cooperation with
the ASV. Using this set-up, the ROV transmits pictures of the seabed back to the support
ship (and thus to the scientist in charge) via a radio link installed on-board the ASV.
A number of AUVs stay dormant either on the seabed or at the sea surface. Upon detection
of interesting features on the seabed by the scientist in charge, a signal is sent to a
selected member of the AUV fleet (via an acoustic communication link installed on-board
the ASV), to dispatch it to the spot detected so as to map the surrounding region in great
detail. Meanwhile, the ASV/ROV ensemble continues to execute the lawn mowing manoeuvre
in search of other sites of interest. With the methodology proposed, sites that
are interesting from an ecological viewpoint are easily detected along the trajectory and
those sites are selectively mapped in high resolution.
To execute the challenging mission above, a number of autonomous vehicles must work
in cooperation, under high level human supervision. This entails the development of advanced
systems for coordinated motion control and navigation in the presence of severe
underwater communication constraints, together with the respective software and hardware
architectures.
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Especially this scenario is also relevant for military application as it is directly related to a
Search-Classify-Map mission of a coastal region using various sensors. The vision of an
AUV, which systematically maps an area while processing data on board and activating
an identification or mine disposal vehicle on demand, is also incorporated in this use
case.
The Challenge
In summary the overall challenge and necessary result of the project is to establish and
realize basic technologies for networked and cooperating heterogeneous unmanned marine
vehicles:
• A user-interface with underlying middleware to plan, check and distribute a coordinated
mission for heterogeneous objects – and for post mission analysis,
• A generic control system for coordinated control of multiple objects in an uncertain
environment including aspects of mission alterations on the fly and triggered
action,
• A swarm navigation solution which enables team members to estimate the position
within the swarm as basis for coordinated control and communication network,
• A generic communication middleware, which enables heterogeneous vehicles to
communicate with each other by LAN, radio and underwater acoustic communication,
• Life sea trials to validate performance of the result shall conclude the project.
4. The Consortium and Share of Work
The Consortium is composed of 9 Partners which share the work under coordination of
the German company ATLAS ELEKTRONIK GmbH.
GREX will start with a short definition phase. The Instituto do Mar at the University of
the Azores, which is dedicated to biological research in the underwater domain, is in
charge to define scenarios and requirements, from which development and trials will be
deducted.
Scientific Methodical Analysis and Research will mainly be performed by the Institute of
Robotics of the Instituto Superior Técnico (IST) (Portugal) and the Technische Universität
Ilmenau, Faculty of Computer Science and Automation in Germany. Both Institutes
combine their theoretical backgrounds to achieve the ambitious goals.
The Bulgarian SME Sciant, experts in embedded systems and communications, will develop
the middleware for inter-process and inter-vehicle communication as well as for
dynamic networking.
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The French research institute Ifremer with its operational experience in underwater
communication will lead the specifications of communication in the GREX system and
provide their Aster X -Vehicle for evaluative tests.
To test the functionality of the joint modules, an overall simulation will be developed by
Seebyte Ltd., UK. They will also be responsible to create the GUI for planning and
analysis of the coordinated mission.
The scientific/technical part of the project, described above, will be framed by an intensive
marketing. INNOVA uses their experience in market studies and exploitation plans
for GREX. MC Marketing Consulting will coordinate the dissemination and promotion
during the project and prepares the web presentation.
IST/ISR ASV Delphim
IST/ISR AUV Infante
Fig. 4: Selected unmanned marine vehicles available to the project
ATLAS UUV SeaWolf
Ifremer AUV Aster x
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5. The GREX team
The developments in the project will be tested using the existing vehicles of the consortium
(Fig. 4 above), which really fulfil the heterogeneous approach. Each vehicle differs
in their sensor equipment, their autonomous capabilities, dynamic properties, and programming/command
language.
To form a GREX-enabled vehicle there is the need to install an additional computer
hardware which runs common modules which are responsible for the coordination, navigation,
and communication tasks, see fig 5. Core element is the Team Handler. This
module holds the team mission plan and is responsible for proper execution and possible
re-planning activities. The control of coordinated behaviour will also be resident here.
The latter functionality will be supported by the team navigation unit which holds the actual
or estimated position of each vehicle in the group. The information is distributed via
the acoustic communication, backed by range measurements to other vehicles.
Vehicle specific
console
GREX
Offline
Interface
GREX
Interface
Module
Proprietary
vehicle
software
( unchanged)
- Vehicle guidance
- Navigation data
- Payload data
Mission Plan
Handler
Mission
Monitoring
Fig. 5: GREX software module overview
GREX Planning
Console
Team Handler
Coordinated
Control
Module
Team
Navigation
IF to
GREX
sensors
Generic software
Vehicle specific
software
VEHICLE No. N
Communication
Module
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As the command language which is used to access the functionality of the modules will
be a general one, there are vehicle dependent interfaces which translate from GREX
language into the vehicle specific language and vice versa. The main gate to the vehicles
is represented by the GIM (GREX Interface Module), which gives access to data
and planning elements available from the vehicle.
Finally, the modules of one vehicle are linked to a GREX planning console, which is the
major planning tool for the team mission, and (if necessary) to the vehicle dedicated
console. Some vehicle still use this console to perform specific vehicle checks and
checking of the translated plan. Also manual control input can be given from here.
The elements combine to a system which is shown below (fig. 6). It is a schematic
graphic only, as the number of participants is not limited. It shows that the GREX system
is composed of the main and specific consoles, as well as different vehicles. All systems
are linked by various means of communication which physical layer may range from
acoustic underwater modems via radio frequency and wireless Ethernet to fibre-optical
datalinks. The Communication Module in the vehicles will select the best method to
transmit the data automatically.
Fig. 6: GREX system overview
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6. Summary and Current Status
The GREX project has been launched in June 2006 within the 6 th framework of the European
Commission. Major goal of this 3 years project is to create a conceptual framework
and middleware to coordinate a flock of heterogeneous unmanned marine vehicles. In
order to get a widely general solution the requirements are routed along mission scenarios
which incorporate all basic elements of civil and military applications.
The project is divided into three major phases which are characterized by the main activities:
1. Specifications and scientific research,
2. Applied research and implementation,
3. Successive trials and final demonstration of results.
Currently the project approaches the end of the first phase. Most specifications are finalized
and research on the challenging topics is in full progress. Beneath methodical research,
hardware tests are performed which includes e. g. trials of different acoustic underwater
modems. Furthermore, a system simulator is under development which allows
testing various software items during the coming development.
The final result will comprise a user interface, based on the SeeTrack software, a common
control system for coordinated mission execution and control, a team based navigation
system and a sophisticated communication system which takes into account needs
for dynamic networking. All control and navigation issues have to be realized under constraints
of the challenging underwater environment which allows only sparse communication.
At the end of the project in 2009, life sea trials will be performed to validate the
results achieved.
More information can be found in the internet. The address of the project homepage is
http://www.grex-project.eu .
7. References
[1] Cardigos, F., A. Colaço, P. R. Dando, S. P. Ávila, P. M. Sarradin, F. Tempera, F.,
P. Conceição, A. Pascoal & R. S. Santos: “Characterization of the shallow water
hydrothermal vent field communities of the D. João de Castro Seamount
(Azores).” Chemical Geology, in press.
[2] J. Kalwa, A. Pascoal, M. Perrier, R. S. Santos, T. Glotzbach, A. Zangrilli, V.
Potchekanski, A. Cormack, M. Jarowinsky: “Coordination and control of cooperating
heterogeneous unmanned systems in uncertain environments”, Annex 1,
EC Project IST 035223, 2006
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