Grex Project

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Handler concept is realized by a Replanning Module, which administrates, executes and validates the replanning commands. While we demonstrated the base functionalities of this concept in Glotzbach et al. (2008), we will go further into detail now and explain the software realization of the team handler and of the algorithms for the first realized and tested Multi Vehicle Primitives. With the already realized functionalities, we are now able to simulate a complete mission from the beginning (vehicles in the water at arbitrary positions) to the end (vehicles have completed their missions plans and wait at defined positions for recovery). This mission will be presented using the developed high-level simulator and employing the original software modules which will later also be used for the real vehicles. 2. Basic conditions within the GREX research project The main idea of the GREX project is to develop a middleware system which enables multiple unmanned marine vehicles to act in a team to perform missions of higher complexity. The basic modules of the mentioned system are shown in Fig.1. Only through the collaboration of the several and specialized modules a team oriented behavior can be realized. Fig.1: GREX middleware system The Communication Module is responsible for the complete communication between several vehicles. Team Navigation estimates the position of all team mates based on a complex estimator structure, the spare position information of the other vehicles and the current track data, like described in Engel and Kalwa (2007). The Team Handler Module realizes the complete management of a team and enables the team oriented behavior on a single autonomous vehicle. Due to the use of different and existing single autonomous vehicles within the GREX research project an Interface Module is necessary which provides a communication link between the existing vehicle hardware and the GREX components. Furthermore we have to deal with several constraints. On the one hand there are vehicles which are able to perform single missions and limited replanning capability. On the other hand we have the underwater communication with very low bandwidth and high rate of information loss. To handle these different constraints and provide a save team operating software as well as mission replanning an intelligent team handling concept is necessary. 3. Multi System Mission Control Based on the defined structure of the Multi Vehicle Primitives, introduced in Glotzbach et al. (2008), we are able to provide a conceptual framework to handle teams of multiple unmanned marine vehicles. The main part of this proposal, the Team Handler core, is shown in Fig.2. 166
Fig.2: Main parts of the Team Handler core This core provides the basic functionality to handle multi vehicle mission scenarios, including strategies to adapt the level of autonomy during the mission execution based on external events, and consists of three main parts which are described in the following chapters. The highest level of the internal build-up is realized with state machines which were triggered by telegrams. These structures constitute the base of information flow between the several GREX modules as well as between the several vehicles within one mission scenario. The telegram types including the build-up of the structure are predefined. This minimizes the occurrence of an error through modified messages caused by module or communication failures. 3.1. Data Management The first part of the Team Handler structure is represented by the Data Management. This passive object stores the information of all vehicles which take part in a mission as well as the mission information itself to provide several data for coordination and replanning purposes. Fig.3: Data management structure The information has to be stored on every GREX vehicle and will be loaded after the Team Handler module is started. The basic structure of this module is shown in Fig.3. Furthermore it provides some simple calculation functionality concerning mission and vehicle data to support the team handling process through a Functionality Interface. These structures can be extended easily in order to add new data or features. Due to the use of an external Data Management the Team Handler core is completely independent from the structure of mission plans or kind of vehicle which should be controlled because the internal structures are still the same. 167
Page 1: Towards Cooperative Behaviour betwe
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Grex Project

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