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

71 The RH4 quadcopter The UAV is a modified RH4 ‘Spyder’, an unofficial term for the airframe of Delft Dynamics’ DroneCatcher, a quadcopter originally designed for capturing multi- copter systems trespassing in high- security areas. “The aircraft’s MTOW is 6.5 kg, so it’s certainly capable of ferrying a 200 g line made from Dyneema or similar,” says Elwin Rath, development and test flight engineer at Delft Dynamics. The RH4 measures 75 cm across from motor to motor, and is 35 cm tall. As Rath notes though, “In the future we may need to develop a bigger UAS for handling larger kinds of lines, but tugboats don’t offer much space on deck for stowing a UAV, so the current size is a good balance for now. “We’ve also sought to minimise the scale of the autonomous tasks – of the calculations being performed by the computer for flight and object recognition and tracking. The more complex the algorithms, the more computer power we need, which has an impact on the size and weight of the flight computer and batteries.” The UAV’s batteries enable a top speed of 72 kph, and a maximum endurance of 30 minutes. Pre-flight sailing “Before the tug leaves its mooring, the heaving line – a light towing line, the first part of the operation to connect the tugboat to the ship – has to be rigged up and attached to the UAV,” Smoor notes. “Both the line and the UAV are stowed in an automated base station. Typically, we take that opportunity to do a full visual inspection of everything, to look for any signs of damage or corrosion across the airframe or propellers.” With the RH4 inside the closed base station, the UAV performs a series of self-tests to ascertain its airworthiness. “It spins its motors, gets feedback from them and the motor controllers, and checks its sensors and avionics. Once the self-checks come back positive, it’s okay to fly,” Smoor explains. As the tugboat proceeds towards the ship it will be handling, the base station also protects the RH4 against damage from any hazards posed by the tug, as well as maintaining a stable environment for charging. The greatest concerns for Kotug before take-off focus on regulatory issues. For every flight over water in the harbour area, a safety assessment needs to be brought to the airport authorities – often days in advance – so that they can approve the flight. “We are working in the port of Rotterdam, which is not far from Rotterdam Airport, where manned helicopters are constantly taking off and landing. We therefore need to establish a geofence for the UAV, and it needs to be approved so that we can use the UAVs to ease the risk of tugboat operations in Rotterdam,” Smoor explains. That has frustrated both companies’ efforts to consistently flight-test the UAV’s iterative updates in a timely fashion, so tests have been moved to a designated area of land owned by Delft Dynamics, with a mock-up of a container ship’s hull. Carrying the line The mission begins once the tugboat is lined up 20-30 m to the port or starboard of the ship, close to the part of the ship where a line needs to be attached. For example, if the ship has to be rotated before the quayside, attaching the line in the mid-forward is best; if the ship has to be moved sideways, the line is best connected in the mid-sides. After the base station opens, the UAV carries up one end of the heaving line, a cable about 6-10 mm in diameter, Delft Dynamics RH4 | In operation We may need to develop a bigger UAS but tugboats don’t offer much space on deck, so the current size is a good balance for now Unmanned Systems Technology | April/May 2019 The RH4 ‘Spyder’ quadcopter, originally developed for Delft Dynamics’ DroneCatcher UAS, is now being developed to meet Kotug’s line-handling requirements