Unmanned Safe Maritime
Operations Over The Horizon (USMOOTH)

Architecture

The system architecture was developed which enabled the right safety claims to be made. This included allowing an operator to take control for launch and recovery.  There were a number of scenarios where operators would not realistically be able to control the vessel, hence the need for the safety monitor.

For example, the communications to the remote vessel have to be via satellite which brings a number of constraints.  There is around a 4 second delay for the return journey of information from the vessel to the operator and the response from the operator to the vessel; roughly 1 second for each up and down link.  A major concern was the avoidance of debris that could simply pop-up and present and imminent threat to the vessel.  There might be insufficient time for an operator, even assuming an instantaneous response to information received, to avoid such situations.   Hence there was a need to allow the vessel to operate autonomously and safely choose a new path.  In a more general sense, it could not be guaranteed that the risk based path planning algorithm could, in all circumstances, correctly avoid other sea traffic, so a safety monitor was also needed.

Finally, communications presented a series of practical and economic problems: it is difficult for remote operators to gain situational awareness from the available information; there is a significant cost for bandwidth to present a detailed enough picture from various sensors hence some compromise is necessary and this affects the ability of the operator to gain situational awareness; and of course, the communications link may fail for a variety of reasons.  It is also recognised that watching a rather grey screen for hours at a time is dull work and attention may wander thus there is a significant case to enhance operator effectiveness by making the safety aspects remote from the operator.  All of these issues and hazards meant that there was a need for high integrity decision making software that would take control  of the vessel in order to maintain safety.

The architecture also had to consider the ability of various types of sensor to provide the information upon which to make decisions and how these sensors are affected by sea state and weather conditions.  We also considered whether and how to account for on-board failures and decided that only certain major faults would be factored into decision making.