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

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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. 2
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- 3
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The European Project GREX: Coordination and Control of ...

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