Sea Technology

JUN 2014

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Page 12 of 76

12 st / June 2014 All these developments have bene- fted from the active sharing of knowl- edge and feld experience among vari- ous groups from universities, research and development centers, and indus- try. Since 2006, two annual events, one mainly in Europe and another in North America, have offered opportu- nities for joining the international com- munity active in robotic sailing to dis- cuss achievements through technical meetings and performance evaluations with feld exercises. These are excel- lent opportunities to assess the results of practical developments, while at- tempting to accomplish increasingly complex tasks, thus encouraging the community to invest in new improve- ments. Such challenges are planned to evaluate the accuracy of course con- trol, speed along different points of sailing, the ability to perform a station- keeping navigation pattern and an en- durance task to verify the aptitude for long-term missions. The FASt Sailboat The FASt autonomous sailboat is a 2.5-meter-long, 50-kilogram un- manned mono hull capable of fully autonomous navigation under sail through a set of waypoints. The sailboat was designed and built during 2007 in the school of engineering of the University of Porto, Portugal, and since then has been evolving to include additional features. The lat- est developments have fo- cused on complementing endurance with trajectory accuracy and the precise execution of sailing maneu- vers like gibing and tacking. A small solar panel is the only source of electric energy that proved to be suffcient for long-term mis- sions due to a low-power computing system and the ability to adapt the frequen- cy of sail and rudder actuation for ad- justing the navigation performance as a tradeoff of accuracy of route, speed and usage of the available power for the electric motors. The boat has a payload capability of a few kilograms, distributed along the interior of the hull, on the deck, or even attached to the mast or the 1.2-meter- deep keel. The interior free volume for installing equipment can also reach a few liters, depending on the form fac- tor of the items. The sailboat can thus be confgured to transport instrumen- tation devices required for a specifc mission. Naturally, adding weight, al- tering the hull's hydrodynamics or the sail plan aerodynamics may negatively impact speed, stability and maneuver- ability. Although the main mission of its embedded internal computer is to per- form all the navigation tasks—route planning, obstacle avoidance, course control, maneuvering—it can also be programmed to acquire data from ad- ditional sensors, in its solid-state hard disk, or even transmit relevant informa- tion via satellite data links. An internal Ethernet network running standard network protocols eases the intercon- nection of additional computers or network-enabled devices. The option for a conventional two-sail confguration (Marconi rig) enabled the capability of upwind navigation, aided by a 1.2-meter-long keel and a 20-kilogram lead ballast bulb (40 percent of the total displace- ment). Both sails are controlled by a single electric actuator, pulling the sails against the wind as in normal sail boats. Although in the current confgu- ration the inability to reduce the sail area hinders the operation with strong Trajectory accuracy while performing a triangular course, allowing a direct navigation to a target waypoint, re- corded near Brest, France. The distance between the two red lines enclosing the route during each leg is 10 meters. JUN2014.indd 12 6/4/14 12:32 PM

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