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80 In operation | Sea Machines/MSRC oil-spill skimmer For example, the existing shift and throttle controls have been replaced by a digital control system from SeaStar Solutions, while the steering system now has a parallel hydraulic pumping and relay system, to better regulate the existing hydraulic system’s distribution of fluid for turning to port or starboard. “Our autonomy system needs to be able to control propulsion and steering,” notes Alex Venetiou, director of engineering at Sea Machines. “In the case of the skimmer, the throttle control wasn’t something that worked easily with our system, which is why we upgraded that in particular. “Moreover, the SeaStar system has a CAN bus interface, so on the one hand it was very easy for us to control, and it also made it really easy to integrate with the actuators used on the skimmer boat’s throttle cables.” Also, an E103 GPS and IMU from Hemisphere were installed for waypoint navigation, a Furuno ERS 4 NXT radar was integrated for obstacle detection and situational awareness, and a Pepwave cellular and wi-fi data link from Peplink was selected for remote monitoring and comms. The vessel has been extensively rewired by Sea Machines and Navtronics to account for the data and power links between the new systems and the existing onboard control surfaces and DC power panel. “There were other requirements,” Venetiou adds. “In addition to installing AIS [Automatic Identification System], our radars needed an ARPA [Automatic Radar Plotting Aid] capability, which enables the radar to assign critical information such as GPS, heading and closest point of approach to a vehicle’s AIS signature as it tracks it. “That information is sent to our autonomy system, so that the SM300 suite can track the target, but it also combines with our collision avoidance algorithms, so the USV can steer clear of the target if necessary. ARPA is largely defined and required by COLREGs, so it’s pretty important for marine autonomy integrations.” For accuracy and integrity of signal processing, control commands sent throughout the USV – such as those between the SM300 main control unit and the SeaStar digital controls for shift and throttle outputs – are delivered securely over an Ethernet-controlled network, using the NMEA 2000 maritime interface standard for comms. October/November 2020 | Unmanned Systems Technology Skimming belts such as these are considered among the most effective and efficient tools for pulling crude oil from the ocean surface, up the belt and into a holding tank Our autonomy system needs to be able to control propulsion. The SeaStar system has a CAN bus, so it was easy for us to control the throttle