Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

20 In conversation | Niklas Nyroth RF integration wrinkles He says the main engineering challenge in this kind of application is to avoid interference between antennas and subsystems. “We have a lot of subsystems. We have transponders with quite large output power, line-of sight telemetry links with 200 km of range and telemetry links over satcom, which is very narrow in bandwidth,” he adds. “So getting all these things to work in concert is still the main challenge, making sure each subsystem works as cleanly as possible so you don’t waste power or bandwidth.” At 4.1 m in length, 7.2 m in wingspan and with a maximum take-off weight of 200 kg, the FX450 is relatively large for a commercial UAV; even so, there is limited space for separating the emitters to avoid mutual interference and for providing antennas with ground planes. The latter must have a radius of at least a quarter of the longest wavelength that the antenna must transmit/receive. Integrating multiple radios takes some ingenuity in the use of composites and in taking advantage of aircraft design features. In one example, the hollow structure of a UAV’s tail allowed the company to install a transmitter and antenna as a single unit, optimising RF connectivity without the need for connectors between them or for shielded cabling, which adds weight and creates losses. “It’s always better to have some extra dB margin,” Nyroth explains The properties of composites can also be used to advantage, he says, with fibreglass-reinforced plastic used for RF ‘windows’ and carbon hybrid materials to block RF transmissions in other areas. “You can also place emitters in layers rather than clusters aboard the aircraft to provide the best possible separation at source,” he notes. Configuration stability A further challenge is the complexity of achieving true system-wide maturity. “It is easy to build something for one test or trial, but to build it for everyday use is more difficult,” he says. “Also, staying true to the configuration – not changing things the whole time – is critical because you can end up chasing your tail. You might get something to work, but at the cost of negatively affecting something else. “For example, one day you might fly for 20 hours and the next day fly at 12,000 ft, but you can’t do them in combination – that’s useless. You can make something more reliable by making it more robust, but we cannot afford that because we are chasing those 20 hours all the time. If we trade some of the fuel for robustness then we end up not being competitive. There is always a very careful balance.” “So actually moving forward – progression on a broad line, in a controlled configuration – is, I feel, a huge challenge for unmanned systems.” Given the difficulty of avoiding co-site August/September 2021 | Unmanned Systems Technology The FX10 (in Nyroth’s hands) and the FX450 are two members of Robot Aviation’s Skyrobot family, which reflect Nyroth’s philosophy of prioritising safety and reliability over pushing the envelope in terms of performance (Courtesy of Robot Aviation) During his time at Mission Technology Systems, Nyroth was responsible for the development of the Buster twin- wing backpack UAV, which featured a gasoline engine and a 150 W starter/generator (Photo: Niklas Nyroth)