Unmanned Systems Technology 021 | Robot Aviation FX450 l Imaging Sensors focus l UAVs Insight l Liquid-Piston X-Mini l Riptide l Eurosatory 2018 show report l Zipline l Electric Motors focus l ASTS show report

64 T hree years ago, Jeff Smith set out to build a small underwater unmanned vehicle costing $10,000 rather than $1 million. That was an ambitious target for a small start-up, but with backing from the US DARPA defence research agency, and an investor, the Riptide team was able to set the project in motion. The aim was to use 3D printing, open source software and commercial off-the- shelf (COTS) electronics, motors and batteries to build a UUV that could travel down to 200 m. The $10,000 cost target and the depth were significant challenges. “We started with a clean-sheet design,” says Smith. “In the past I’ve been the chief operating office of BlueFin Robotics and General Dynamics, and when you look at the pricing, those UUVs cost $1 million for a reason – there’s a lot of complexity.” The resulting A-size UUV – with a 4.875 in (124 mm) diameter, the same as a sonar buoy – costs $12,000 and can travel at 2-3 knots at depths of 200 m for up to 40 hours using standard alkaline batteries. Riptide has since branched out to larger sizes, dramatically greater depth capability and longer range by using lithium and even aluminium-air batteries. The control electronics are based around the BeagleBone Black controller card. It is designed for the Arduino ecosystem, and has a common size and connector to add peripheral boards called shields. This allows inexpensive boards to be stacked together, cutting down on the cabling needed. Open source software Initially the team used the open source Robot Operating System (ROS) running on Linux. However, it found that the Mission Oriented Operating Suite (MOOS) software, developed at the Massachusetts Institute of Technology, was more suitable. This is a set of open source C++ modules for providing autonomy on robotic platforms but which are optimised for autonomous marine vehicles. The modules have been optimised to run on the BeagleBone Black card in the Nick Flaherty explains how this UUV family uses open source software and COTS components to slash the cost of undersea missions Plunging price point The design of Riptide’s UUV was driven by a desire to produce a small vehicle at a fraction of the cost of more complex craft August/September 2018 | Unmanned Systems Technology