Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

90 method might mean installing separate battery packs for the payloads, meaning extra wiring harnesses, more noise protection and other complexities across the vehicle design, so using ESCs with a sinusoidal output waveform has really enabled us to keep the architecture simple.” Structure The design and construction of the Sonobot’s hull have focused on some key properties. The first is low drag – the overall shape gives the hull a low profile, so high winds and gusts do not significantly disturb its survey patterns. In the same vein, the floats have a wave-piercing design to reduce the impact of turbulence on the Sonobot’s movements. Another key target has been robustness. To that end, the main hull is made from a basalt fibre composite from Alpha Sigma. The material is new to unmanned vehicles, and until recently it was also new to EvoLogics. “It is stronger than fibreglass, closer to carbon composite in strength but without the drawbacks of carbon fibre,” Dr Lange says. “It is more flexible than carbon, it doesn’t conduct electricity as much and it’s very transparent to antenna transmissions. It was made in a lightweight sandwich structure, with a foam between two skins of basalt composite for an overall weight around 1 kg/m 2 . “It’s also very hard – you can step on it and there are no cracks or stress. We’re not sure why it isn’t better known among unmanned systems engineers; the company that makes it also supplies it to VW, Bentley and other automotive and motorsport users.” In addition to robustness, the structure has been designed with transportability – particularly between lakes and surveyors’ offices – in mind, to ensure easy disassembly or allow the USV to be folded into its carrying case for transportation by road. The hull therefore has four hinges: one 5 cm above each float, and one atop each of the two legs connecting the floats to the main body. “The hinge design has also been optimised so that only a single one on each side is needed, which makes manufacturing easier,” Dr Lange adds. Navigation and operations As mentioned, EvoLogics switched from much of its COTS computer systems used in the Sonobot 3 to a more compact in-house system in the Sonobot 5, and the same applies to the GNSS. The GNSS receiver is integrated inside the USV’s high-power wi-fi unit. It is a differential dual-band L1/L2 GPS receiver, with RTK processing available via a base station or GPRS modem to give real-time position accurate to 2 cm and altitude to 4 cm. It is also fused with an Xsens MTi AHRS for its inertial aiding needs. Notably, by designing the computer architecture in-house, the company can April/May 2021 | Unmanned Systems Technology The hull is constructed from basalt fibre composite, and features four hinges for easy folding, storage and carrying EvoLogics has successfully trialled its object recognition software using the Sonobot 5’s sonar in lakes