Software architecture

Gavia's control software is organized in a unique distributed architecture modeled on the division of responsibilities among the hands of a manually controlled vessel. The Intelligent Artificial Crew (IAC) comprises a full crew responsible for the safe navigation of the vessel together with scientific personnel responsible for meeting the goals of the mission.

Reliability

This has been assured through modular design and clearly defined responsibilities of the Intelligent Artificial Crew members that are common to all versions of Gavia irrespective of the number or types of modules installed. Members of the crew run as separate independent processes on the networked PCs, while time-critical functions are handled by the real-time microcomputer/micro controller network.

Mission execution

Mission execution follows a mission plan expressed in Gavia's powerful XML based AUV Scripting Language (ASL). The mission plan can contain both fixed and dynamic paths. Fixed paths consist of 3D waypoints and 3D lines or patterns such as zigzag or lawnmower pattern. Dynamic paths are determined in real-time by an onboard scientist analyzing sensor data. In addition the ASL language allows dynamic switching between paths based on events flagged by scientists, such as a "found" event or a "lost track" event. Throughout the mission sensors can be turned on and off as required.

Exception handling

Reaction to exceptional or critical operational conditions is handled by the captain of the Intelligent Artificial Crew, who with the aid of his crew oversees the proper running of the vehicle. This relieves the planner of a mission of the task of foreseeing every possible situation and leaves him free to concentrate on the goals of his mission.

Extensibility

A variety of missions can be specified in the mission plan using Gavia's powerful ASL language. Further functionality can be added by incorporating additional specialist members into the crew capable of solving application specific tasks. Since crew members communicate using industry standard CORBA interfaces, they can be written in any of a number of programming languages offering CORBA support. Similarly crew members can be accommodated on optional further PC computers to meet specific processing needs or operating system requirements.

Testing

Gavia has a built-in simulation mode that enables the testing of complete missions prior to deployment. Simulated missions are executed by the same crew members following the same mission plan as real missions. The simulator receives control output from the pilots and accurately models the dynamic response of the vehicle and its interaction with the environment and makes that information available to the crew via virtual sensors.