Unmanned Systems Technology 025 | iXblue DriX I Maintenance I UGVs I IDEX 2019 I Planck Aero Shearwater I Sky Power hybrid system I Delph Dynamics RH4 I GCSs I StreetDrone Twizy I Oceanology Americas 2019

72 In operation | Delft Dynamics RH4 with the rest of it bundled inside the base station. As it approaches the approximate height of the container ship’s deck, the tugboat crew can grab the other end of the heaving line and attach it to the floating line – the main towing line. Previous collaborations have contributed vital knowledge to Delft Dynamics’ partnership with Kotug. As an initial example, Rath explains, “We’d previously taken part in a project called ASIMOV, where we sat a box-like base station on top of a reconnaissance or armoured fighting vehicle. “A tethered UAV would launch and carry out a survey around the vehicle, to save soldiers or operators from having to leave the safety of the vehicle and do it themselves, while also providing a higher and therefore better vantage point. “That enabled us to improve our systems’ stability when launching from moving vehicles. It was harder for this project though because of the added water dynamics, but Kotug wanted similar principles to ASIMOV – to stow the UAV safely in a box-like base station, before launching it from the box and ascending stably with a line attached.” After the ascent, the operator identifies the correct or ideal Panama chock – the small, ring-like structures spaced around the circumference of ship decks for securing lines – via a camera on the tug’s deck. They lock onto the target chock, and the UAV receives the target lock and flies over to it. The object recognition and target lock capabilities were key developments from the DroneCatcher project, which Delft Dynamics has modified to derive solutions for Kotug’s requests. “The DroneCatcher would detect UAVs using an EO camera, and after detecting a target we’d ‘lock’ it, meaning the heading and tilt of the net-gun would be automatically controlled by the camera lock on the target,” Rath says. “We use the same sensor and software architecture with Kotug’s project; it’s just a matter of altering and training the algorithms that detect UAVs to detect Panama chocks instead.” The RH4 will typically spend between 3 and 10 minutes flying. Given the 20- 30 m distance between the tug and the ship, travel time is short, and most of the mission is spent hovering in front of the chosen Panama chock to carefully deploy the line being carried. As with object recognition and line- carrying, Delft Dynamics has carried over experience from other projects to provide sufficient protection on the vehicle against saltwater ingress as it flies over the water. “We’re working on an order from the Dutch Navy, which is about to fly our UAV from its ships in salty environments,” Rath explains. “For these UAVs, we put a lot of effort into choosing the right aluminium, carbon composite and other materials to build our UAVs, to make sure they don’t corrode. “We’ve also looked for – and acquired – electric motors which are closed and can run without saltwater getting into the bearings,” he says. “A lot of manufacturers claimed theirs were good enough, but we were sceptical and tested a number before choosing.” Delft also made judicious use of seals on fasteners and other points where components are designed to be removed or replaced, and applied cement-like adhesives where permanent sealing needed to be assured. The seals were designed by Delft Dynamics according to their mechanical requirements, and cut to size from rubbers such as NBR by its supplier. After most of the distance to the ship is cleared, the UAV relies on a laser rangefinder to home in on the targeted chock while avoiding bumping into the freighter hull. “For the DroneCatcher, it was always critical to know the distance of the rogue UAV being targeted, so we integrated a laser rangefinder to aim at it April/May 2019 | Unmanned Systems Technology The heaving line is stowed with the UAV inside its base station, so that the RH4 is already carrying one end of the line as it ascends to begin the operation The software is the same as in the DroneCatcher project; it’s just a matter of altering the algorithms to detect Panama chocks instead