Unmanned Systems Technology 002 | Scion SA-400 | Commercial UAV Show report | Vision sensors | Danielson Trident I Security and safety systems | MIRA MACE | Additive manufacturing | Marine UUVs

78 Insight | Marine UUVs their position relative to a known starting point, AUVs use gyroscopes and doppler velocity logs that keep a record of the speed and direction of the craft that is independent of the onboard sensors, but to do so they need highly accurate clocks. To have an accurate position, AUVs typically have to surface at regular intervals in order to obtain a fix of their position from a GNSS satellite such as GPS. This reduces the area an AUV can survey during a given mission. Plextek’s investigations have shown that an AUV can substantially improve its position and time estimate by combining its own time estimates with those from a number of nearby craft, via an appropriate Kalman filter, an algorithm that looks at a series of measurements over time to produce better estimates of an unknown variable than those based on a single independent measurement. Variants of it are used for monitoring the condition of the electronic components in an autonomous system. By sharing information, the AUVs reduce error and drift while minimising their dependence on the GNSS network. If multiple AUVs were operating, they would be able to surface for a GNSS fix less often, as only one would need to resurface to improve the time and position estimates for all the other nearby AUVs. This approach could use quantum clock technology to provide more accurate timing and navigation systems for underwater systems. To this end, researchers at the UK’s National Physical Laboratory are using hollow fibres filled with caesium atoms to create miniature atomic clocks that can provide high accuracy for navigation systems in small, light packages with low power. A commercial chipscale one-dimensional (1D) quantum accelerometer for inertial navigation is expected in the next two years, with a 3D accelerometer within four years. Another approach for handling fleets of AUVs is being developed by SeeByte, in Edinburgh, which is working with the UK’s National Oceanography Centre (NOC) to develop control software for the Marine Autonomous and Robotic Systems (MARS) group in the NOC. MARS has recently acquired a large fleet of torpedo-style AUVs that are powered by ocean currents. Commonly called gliders, they are made by Teledyne and Kongsberg (Norway’s major defence contractor), but each type has its own interface and processing tools. SeeByte is modifying its SeeTrack software suite to provide a common interface for all the gliders, regardless of the manufacturer. By combining all the mission plans and monitoring in a single workstation, the NOC will be able to manage larger fleets of gliders without putting additional strain on the operators, and data from these missions will be consolidated on a shared database, allowing data to be easily analysed. The Kongsberg SeaGlider used in the NOC fleet uses a novel propulsion system. Rather than an electrically Spring 2015 | Unmanned Systems Technology Kongsberg’s Hugin autonomous underwater vehicle, which is targeted at subsea surveys down to 4500 m If multiple AUVs were operating then only one would need to resurface to improve the time and position estimates for all the nearby AUVs