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

60 camera and sensors. The thrusters can be adjusted for vertical thrust to allow the craft to travel to the working depth, and the Opensea software includes a ‘set and forget’ auto-depth function that can be easily adjusted. The motor controllers in the thrusters are tuned for responsiveness. When used as a remotely operated vehicle via a joystick, this provides fine control for accurate positioning. The gain of each motor controller is independently adjustable to give an operator that control and positioning. The designers at VideoRay have also kept maintenance in mind. As an example, the proprietary cartridge motor shaft seals can be visually inspected without being removed. When it is time to replace them, it usually takes less than 5 minutes and can be done in the field instead of the labour-intensive process of disassembling the thruster and refilling a grease galley. Fouled propellers can also be cleared and replaced easily if necessary. These brushless thrusters are also available independently of the vehicle to anyone. This option includes the complete thruster sub-assembly. The propellers are designed to be used on counter-rotating thruster arrangements to eliminate torque roll or yaw. They are identified by their pitch orientation, using left and right based on their pitch. The convex edge of the propeller blade is the leading edge during motion that is considered forwards for that thruster. For sonar, VideoRay has integrated Oculus M multi-beam sonar sensors from Blueprint Subsea. Measuring from 125 x 125 x 62 mm, they weigh less than 400 g in water. They were chosen because the dual- frequency capabilities of the M750d (750 kHz, LF)/1.2 MHz, HF) and the M1200d (1.2 MHz, LF)/2.1 MHz, HF) allow for long-range sensing at the low frequencies, with higher resolution from the higher frequency transmissions to provide more accurate data of objects under investigation. The Defender can also use an ultra- short baseline (USBL) comms system from Seatrac. The X100 micro-USBL tracking and data modem uses a broadband spread-spectrum signalling scheme to track the position of the ROV, and can be also be used to transfer data to and from the Opensea operating system for the navigation and positioning functions. It can also provide remote and local depth information, water temperature and AHRS information. Power delivery Power for the craft is supplied via a tether cable that links the craft to an operator and feeds back the video and sensor data using an auxiliary pair of independent conductors. It requires an external power source capable of producing 100-240 V DC at 50 or 60 Hz with a minimum steady-state capacity of 3 kW, which supplies 1500 W to the craft. The cable for the tether consists of the conductors, a Kevlar strengthening line, any flotation elements that are needed to provide a neutral or floating tether, and an outer jacket, which all combine to provide a breaking strain of 680 kg. It is available in three types – Negative, Neutral and Performance, where the December/January 2019 | Unmanned Systems Technology The design of the thruster guard is a key part of simplifying the Defender’s maintenance (Courtesy of VideoRay) It is no mean feat to build a modular UUV that is small enough to carry on an airliner. Dropping the battery is one way forward