Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

58 Digest | VideoRay Defender use and simplifying the operation of such a platform, particularly the performance of automated control modes such as auto heading and depth.” VideoRay and Nortek worked closely together to build the DVL directly into the Defender’s frame and install the cabling to communicate with Greensea’s software hub. Meanwhile, Greensea and Nortek collaborated to ensure that data from the DVL could be integrated with information from the other sensors to provide a cohesive overall picture of location, speed and heading within the Opensea software. That allows the Defender to hold its position, even when shifting the focus of the position sensor from the sea bottom to a vertical surface such as a wall or ship’s hull. “The MSS does really well with high degrees of pitch [as in at steep angles from the horizontal], which I didn’t expect would be possible. It can hold steadily at 60 or 70 º pitch, and a lot of that is due to the Nortek DVL,” says Colin Riggs, director of product development at Greensea. The Defender’s ability to lift well over half its own weight is another reason why it needs the precise positioning from the DVL1000 and other sensor subsystems. For example, one potential use for the Defender is in subsea mine clearance. To do that, it needs to be able to carry a sizeable payload of explosives and then position itself accurately to drop them in the right place before retreating. There is little room for error in such sensitive assignments. Thruster design The Defender’s lift capability comes from the thruster design. The seven thrusters, each using 400 W of power, are coupled with hydro-dynamically optimised propellers and nozzles, and produce up to 27 kg of forward thrust for the 18 kg vehicle, and a thrust-to-drag ratio of more than 2:1. Four of the thrusters can be directed horizontally and three vertically to provide more lift than other platforms (at 23 kg of thrust) so that the craft can operate in currents that would be unsafe for divers. The thruster placement on the Defender, and counter propeller rotation, provide a zero turning radius and improve the agility of the frame as well providing a stable platform for the December/January 2019 | Unmanned Systems Technology Nortek’s doppler velocity log installed in a Defender (Courtesy of Nortek) The Defender inspecting a submerged ship for training purposes (Courtesy of VideoRay) The MSS does really well with high degrees of pitch, which I didn’t expect would be possible. It can hold at 60 or 70 º