Uncrewed Systems Technology 051 l Primoco One 150 l Power management l Ocius Bluebottle USV l Steel E-Motive robotaxi l UAVs insight l Xponential 2023 p Issue 51 Aug/Sept 2023 art 2 l Aant Farm TPR72 l Servos l Tampa Deep Sea Barracuda AUV

32 make a big difference in our GCS’s performance,” Fojtik explains. Vector’s customisability has enabled close integration between it and the array of onboard sensors for airspeed, air pressure and other key inputs so that missionspecific functions such as autonomously following a target while staying within LOS range can be performed. “If we’d made our own autopilot, or tried a totally new one from a newer company, we’d never have been able to prove out all bugs and failure modes on our flight hours alone,” Fojtik adds. “UAV Navigation has many customers, so we know they go through terabytes of real-world data to optimise their platform. We don’t have to encounter a bug ourselves before it gets fixed – statistically, someone else is likely to encounter it, report it, and get it taken care of before it affects our missions.” Control architecture The onboard network has been designed to be as streamlined as possible while still incorporating two-way closed loops, such as each servo reporting back to the autopilot when a movement order has been executed. The Vector-600 is the master controller for commands and power distribution through the central box, being compatible with CAN, serial, PWM and analogue buses as standard. Payloads are controlled via Ethernet, and through Visionair a protocol proprietary to UAV Navigation can securely stream data prioritised by the end-user. Cable harnesses are made inhouse, with military-grade connectors bought from TENEO 3000. The network makes the UAV fly-bywire, each control surface being actuated by its own rotary servo, and electrically distributed and optimised for no friction or dust ingress. There are 10 flight control surfaces in total: two ailerons, four flaps (one inner flap and one outer per wing) and two rudders and elevators at the tail. Primoco gauged the durability and consistency of the servos by building its own actuator test rigs and running millions of cycles on individual units to ensure each could last 1000-2000 hours of operation. “And to reassure authorities, we limit each servo’s service life to 100 flight hours,” Fojtik comments. “It’s a huge safety margin, theoretically one-tenth or twentieth of their lifespan, and I don’t think we’ve even had one servo fail, but that’s necessary for flying defence missions safely. “To minimise friction, we’ve used Teflon parts in places to avoid needing lubrication, and we laminate each control surface so there are no hinges. And we’ve validated the mechanical robustness of that lamination in material tests and fatigue tests. “In flight, we continually monitor servo voltages, among other parameters, as overvoltages can be a sign of friction or failure at the component level. If that happens, an alarm pops up so that the GCS operator or autopilot can disengage the problematic servo.” Primoco has also designed the One 150 to be positively stable about its CoG, with the balance and attitude-holding of a training aircraft rather than, say, a fighter jet (which is inherently unstable) such that it could fly with all its control surfaces trimmed. Some aircraft can gain manoeuvrability by being designed as negatively stable, but the loss of just one navigation sensor input can make it nigh-on impossible for the autopilot to compensate and correct its flight, or make an emergency landing. Fojtik says this was a specific requirement from one of its key defence customers. “Even STANAG 4703 doesn’t specify that. Although that certification is important to us, if all we did was design the UAV to STANAG 4703, it would meet only 50% of that customer’s needs. In war, as in all markets, listening to customers is key.” Taxi, take-off and landing For anti-collision and air traffic awareness, Primoco typically integrates Sagetech’s MX-Series of ADS-B In and Out systems. Through ADS-B In, the GCS can receive the positions of other aircraft and their IDs. However, the regulations are unclear on how to execute automatic course deviation, so Primoco has not implemented this yet, or autonomous taxiing to take-off points, although that is technologically achievable. The frontal landing gear integrates a nose wheel servo for by-wire steering during taxiing; that, plus the engine throttle servo, makes 12 servos in total on the UAV. Pre-flight checks and take-off take around 2 minutes. “The rear landing gear was originally designed as a banded metal structure, but after hitting the runway, the UAV August/September 2023 | Uncrewed Systems Technology A radar altimeter enables safe landings even when GNSS is being jammed or spoofed