Docking with the Habitat
Underwater Docking Of Vehicles Using Optical Guidance
The AUVs will need an external docking system, while they recharge, download instructions, as well as upload information. This is a relatively easy process. The docking structure is simple a skeletal funnel with approximate diameter of the AUVs, (which is about 60 cm). Within this cone are the necessary ports and connections to allow download of data and energy recharging. The difficulty arises in getting the AUV to dock autonomously. This problem has been solved in different ways, but the best option seems to be that provided by the navy with their "Distributed Surveillance Sensor Network" .
A docking system, known as the Universal Socket is used. Initially, the AUV is attracted to the site by initial homing using high frequency acoustics. That means that the socket sends out an acoustic signal, which allows receivers on the auv to know where the dock is located. For precise alignment between the vehicle, and the dock, optical terminal guidance is used.
A light emitting diode is located on the underwater dock. When light propagates underwater some is absorbed by the medium, others are scattered. A few photons travel undeflected. The detector can compare signals reaching it at different angles and determine position of the dock. The photodetector on board the AUV is housed in a titanium cylinder, approximately the size of a beer can.
Latching mechanisms within the universal socket ensure that the AUV is held in place while it downloads its data and recharges its batteries.