USE Network launch I UAV Works VALAQ l Cable harnesses l USVs insight l Xponential 2020 update l MARIN AUV l Suter Industries TOA 288 l Vitirover l AI systems l Vtrus ABI

52 Insight | USVs shallow water currents can sometimes move the nodes around). “We’ve also installed Knudsen’s single- beam echosounder on the Mariner, as a means of checking the depth of each node,” Pederick adds. “The Mariner has a custom-fit moon pool as well, which allows us to customise a requirement-specific payload and bolt it into the pool. If the customer decides later that they want a multi-beam echosounder, we’ll make one for them that fits in place of the single- beam system.” The Mariner measures about 5.8 x 2 x 2 m, is powered by a Yanmar 195 hp diesel engine with a HamiltonJet waterjet, and has seismic survey software from ION Geophysical, which provides the interface between the Mariner’s sensors and the mother vessel. “We’ve also added hybridisation and back-up propulsion in the form of batteries and Torqeedo Cruise electric thrusters,” Pederick says. “Those interface to our control system via a redundant computer and link, so that if the engine fails the USV can keep operating or just sail up to the lead vessel or port so that technicians can see what’s gone wrong.” Hydrographic surveys Demcon Unmanned Systems has designed the D-USV, to enable precision navigation in shallow waters, GNSS- degraded areas and environmentally sensitive locations. Fedor Ester, the company’s co-founder and managing director, explains, “A former civil engineering classmate of mine who now works for the Van Oord dredging company wanted to know how unmanned vehicles could help their survey operations. “They liked our prior experience in developing unmanned autonomous systems and our technological focus on path planning and GNSS-denied navigation solutions, so we looked at their current vessel and started developing the D-USV around their equipment and processes to provide equivalent or better survey capabilities in an autonomous way.” The D-USV is a fully electric vessel measuring 2.5 m long, 1.1 m across and 1.0 m in height. The height above the water surface is between 0.8 and 1.5 m, depending on the position of the adjustable bridge, with a draft up to 0.4 m and an empty weight of 198 kg. For payload integration, its design includes a moon pool that measures 63 x 44 x 39 cm. It can integrate up to 100 kg of sensors, including a RC winch for depth measurements, and an antenna bridge bracket offering 95 x 16 cm of space that can mount up to 5 kg of additional electronics. The hull is aluminium, and features multiple bulkheads and watertight deck hatches that are being trialled as further payload mounting points. Propulsion comes from three rim-driven thrusters (two at the stern and one at the bow), which provide a cruising speed of 9.5 kph and an autonomous mission speed of 5 kph. The first D-USV was delivered to Van Oord in April, and immediately began surveying areas of key waterways where dredging might be most urgently required. As these areas are prone to GNSS signal loss, GNSS-denied navigation capabilities are rapidly undergoing r&d. “When you’re near or underneath metallic structures, which are common in the harbours where surveys are needed, you can lose your GNSS fix, so it’s important to be able to navigate the waters using perception sensors,” Ester notes. “Lidar or vision-based navigation solutions enable them to keep accurately surveying and geo-tagging the riverbed, without any additional equipment.” At the time of writing, Ester and his team were testing a Lidar-based system for their collision avoidance and GNSS- degraded navigation systems, using an Ouster Lidar installed atop the sensor bridge. They will add other sensors such as vision-based ones in the future. Conclusion USV hulls are being engineered with ever- greater precision and quality, while building greater electrification and redundancy into propulsion systems – which is unlocking more and more hours in repeated missions with reduced downtime. In the meantime, the technologies they use are maturing, and end-users are becoming more proficient in working with them. They should therefore be expected to request (or be open to adopting) a wide array of additional new technologies, to further enhance their gains from autonomous maritime operations. June/July 2020 | Unmanned Systems Technology The D-USV uses a sensor bridge for mounting sensors and cameras for GNSS- denied navigation sensing (Courtesy of Demcon Unmanned Systems)