CADDY project - how robots get close to divers

Divers operate in harsh and poorly monitored environments in which the slightest unexpected disturbance, technical malfunction, or lack of attention can have catastrophic consequences. They manoeuvre in complex 3D environments and carry cumbersome equipment, while performing their mission. The CADDY project aims to overcome such problems, by establishing an innovative paradigm, i.e. introducing in the field a robotic diver companion. This last can accompany the diver during his/her mission, being a useful companion in a twofold manner: i) helping the diver to accomplish his/her mission; and ii) monitoring the diver actions and physical state, in order to provide help (e.g. signaling problems to the surface ground station) in case of emergency. The CADDY project replaces a human buddy diver with an autonomous underwater vehicle and adds a new autonomous surface vehicle to improve monitoring, assistance, and safety of the diver's mission. The resulting system plays a threefold role similar to those that a human buddy diver should have: i) the buddy observer" that continuously monitors the diver; ii) the buddy "slave" that is the diver's "extended hand" during underwater operations performing tasks such as "do a mosaic of that area", "take a photo of that" or illuminate that"; and iii) the buddy "guide" that leads the diver through the underwater environment. In such a way to be effective once employed in such a context, the robotic buddy must exhibit cognitive behaviour through learning, interpreting, and adapting to the diver's behaviour, physical state, and actions. Moreover, in order to be "accepted" by the human divers, the robotic buddy should also interact with them in a way that result natural to the humans. For this reason, the robotic buddy has been endowed with the capability to understand diver sign language. To this regards, since this sign language is composed by few gestures and since here is the need to issue more complex commands, a completely new language, called CADDIAN, has been created, using the diver common gestures plus some more symbols. The companion robot is thus able to understand complex commands (or even entire sentences containing more than one command), validate them using the CADDIAN syntax rules and promptly responding to them by executing the requested actions. In the paper, the CADDY concept will be presented in details, and the robotic system will be described. The CADDIAN language and some hints about the related gesture recognition process will be introduced as well.