EU research project GREX (January 2010)
With the final final sea trials in early November 2009 the EU research project GREX was successfully terminated. These sea trials took place at the Atlantic coast around the Portuguese city of Sesimbra. The main objective of the trials was to verify the concepts developed for the simultaneous operation of two AUVs and two catamarans, which relied on inter-vehicle communication to perform totally autonomous a series of coordination tasks as cooperative path following, go to formation manoeuvres and cooperative line of sight target following. These achievements represent an important final project goal for the GREX consortium.
The final trials featured inter-vehicle communication and coordination of a fleet of two AUVs and two catamarans as the main focus. In order to gather useful data and experience in realistic condition all 4 vehicles were equipped with the modem chosen by the GREX consortium.
The potential for interference between vehicle noise and VEMCO acoustic fish tracking tools was also tested during real multi-vehicle missions. All vehicles were tested as carrying platforms for self-contained VEMCO receivers VR2 and VR2W. VEMCO V16 coded depth sensors transmitters were used to simulate both fixed and mobile (onboard) targets.
During the final tests different autonomous tasks which represent the basic ingredients of larger and more complex swarm missions have been successfully tested in Sesimbra. As a first step, a “Coordinated Path Following” of all four autonomous vehicles has been achieved. Each vehicle runs its own tack while “talking” to each other and adjusting their speed in order to coordinate the group and to reach the planned formation. Eventually the fleet of all four robots follows the path and keeps the desired formation pattern.
As a second step the “Go to Formation” manoeuvre has been tested. The procedure is the same as for the “Coordinated Path Following” with a time-varying formation pattern. The vehicles were scattered after the deployment and calculated their path towards a starting point without any conflicts.
The final sea trials step focused on one of the early envisioned GREX scenarios:
a formation of vehicles receiving the location of a target throughan acoustic channel and tracking it while keeping the desired formation. The new CLOST2 (Coordinated Line of Sight Target Tracking) algorithm proved to work in the real world with two tracking autonomous surface vehicles and a manned vessel (equipped with an acoustic modem) playing the role of the target.
In summary it has been verified that all vehicles we successfully able to keep a spatial formation in a self-organized manner. The main idea behind this is to create a wider sensor coverage aiming at high efficient search or mapping missions.
As a main project result it has been achieved that a preliminary GREX-box is now available which can turn already existing vehicles into cooperative robots to fulfil swarm applications. This package consists mainly of a bunch of software modules which communicate to other GREX-systems, care for navigation updates, and control the cooperative movement of the group.
The GREX project has been launched in June 2006 within the 6th framework programme of the European Union. The major goal of this 3 and a half year project was the creation of a first operational framework and middleware to coordinate a flock of heterogeneous unmanned autonomous 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 status achieved by the end of 2009 will allow using the GREX system as a stepping stone for real multi-vehicle applications. Emphasis of the future development needs to be placed on payload data exchange in order to maximize the effect of spatially distributed measurements as well as to increase the reliability of the acoustic communication.
Besides the tested scientific scenarios future applications for swarm robots could be pipeline tracking and inspection, magnetic field mapping of seabed areas as well as archaeological and also military applications. To the successful end of the EU research project a GREX movie with essential results was introduced by the consortium.