Issue 40 Unmanned Systems Technology October/November 2021 ANYbotics ANYmal D l AI systems focus l Aquatic Drones Phoenix 5 l Space vehicles insight l Sky Eye Rapier X-25 l FlyingBasket FB3 l GCS focus l AUVSI Xponential 2021

47 water over a given range of speeds. The first major choice to come out of this was a semi-planing monohull optimised for moderate speeds and with a traditional form optimised for a convenient layout of internal systems. “There are some advantages in terms of structural simplicity, and it is economical for manufacturing compared with a complex specialised catamaran design, for example,” he says. “That is part of how we are optimising the costs while also gaining easy access for maintenance and inspection. We are very much aware that this is a workboat, so it needs to be practical.” There are also benefits to hull strength for a traditional monohull – the internal framing, bulkhead and top deck provide greater stiffness than that of a catamaran of the same size and weight. Hope says the marine-grade aluminium selected for the hull provides a lot of flexibility in terms of configuring the internal framing and positioning the equipment, both during development and in making customer-specific adaptations, thanks to aluminium’s weldability. “In terms of maintenance of the hull and adaptability, aluminium was the best choice,” he says. While aluminium has inherently excellent resistance to corrosion without the need for a coating, all the hull fittings were chosen to minimise the potential for galvanic corrosion, and the vessel is fitted with sacrificial anodes and a galvanic isolator to increase overall protection. “If we are up against a steel quay wall or another ship in port, the system will balance out the potential differences so that the boat will not experience corrosion,” Hope explains. “It also protects the boat when it is charging, as you can get a slight potential difference between the hull and the quay that would accelerate corrosion.” Sensor payload support Designing the vessel around the payload also involved placing the sensor support platform as close to the centre of gravity (CoG) as possible, and building the mast as a tensioned A-frame structure to ensure that any movement between the GNSS sensors, the INS and the primary survey sensor is kept to a minimum. Also, the sensor platform under the hull is positioned as closely as possible to the INS so that the motions measured by the latter are as similar as possible to those affecting the sensor. This minimises the correction factors that must be applied to the output of, for example, a multi-beam echo sounder. “We need to know the global position of that echo sounder as accurately as possible, and the whole system moves less when it is at the CoG of the vessel,” Hope says. “If you have the system at the front or the back and the vessel pitches, there is more movement at the sensor, so you need more corrections.” Aquatic Drones Phoenix 5 | Digest Unmanned Systems Technology | October/November 2021 System overview shows the Phoenix 5’s key subsystems and how they connect via USB/serial, RS-485, CAN and EtherCAT links, all managed by a PLC