Uncrewed Systems Technology 044 l Xer Technolgies X12 and X8 l Lidar sensors l Stan UGV l USVs insight l AUVSI Xponential 2022 l Cobra Aero A99H l Accession Class USV l Connectors I Oceanology International 2022

34 Dossier | Xer Technologies X12 and X8 volume and flow rate of cooling air or water done correctly, as well as venting air and exhausting it out afterwards.” By contrast, Xer uses a by-the-book approach to its fuel management, given that such components are well- understood and widely available. Aside from the pumps, hoses and many other components, some novel features are installed. For instance, tank foam, such as that used in Formula One cars, is fitted around the fuel tanks to prevent spatters of gasoline in the event of a crash. Engine control and cooling are managed by Xer’s proprietary engine controller, which processes data inputs from across the power system to do so and transmits much of them to the GCS. Development of the controller began soon after Xer’s initial purchase of an ECU that was not designed for use on multi-rotor platforms yielded improper throttle control for running the engine in precise power bands. “We mentioned speed and heat sensors, but we don’t want to overload or distract the user with unnecessary information,” Skantze notes. “It is safety-critical during r&d to keep an eye on things such as crank rpm, cylinder head temperature [CHT], exhaust gas temperature and, if applicable, coolant temperature. “In general though, not all of those are urgent for the end-user. If we had to keep just one it would be CHT, because if that’s normal it pretty much always follows that the rest of the power unit is fine as well.” The ECU is worth mentioning alongside the core challenges of cooling, vibration and power management, as it took a lot of design and programming work to tune it for safety and efficiency. Whenever the autopilot sends rotor commands to the ESCs, power management commands must also be sent to the PMU to ensure that power is distributed correctly and that not too much strain is placed upstream on the engine, battery or generator. Logic has therefore been programmed into the ECU to stabilise the engine and generator, and thus stabilise control over the UAVs. Electric power The generators are modified three- phase brushless AC units from Sullivan UV (now Acutronic Power Systems) that are designed for direct drive on engine crankshafts and use neodymium permanent magnets. The X12 uses a 7.2 kW alternator, although peak electric power delivery is capped at 6.5 kW, while the X8 has a 5 kW system. “Originally we used a hybridisation ‘kit’ that another supplier put together for us, but we didn’t like the results because of various quality issues,” Skantze says. “We had to break down and analyse each component in detail to ensure we’d have no issues with generating electric power. “It has been a rather long and unexpectedly complicated process, indicating that it has not been done before for our type of product. Many components, such as Sullivan’s, are high- end products for sure, but even here we’ve had to make modifications to cater for our needs.” To ensure optimal efficiency and minimal thermal losses in the PMU, much of the connection soldering was redone in-house after receiving parts from manufacturers, but it acts largely as a slave to the autopilot and carries no intelligence of its own. “It has however been a major mechanical and thermal challenge,” Skantze recounts. “Time and again, the expensive and much-vaunted parts we bought for it kept failing, without any clue most of the time as to why, so it took time to climb that learning curve and find the right PMU component supplier. “Our supplier is a world leader in such technologies, and has helped make the PMU much lighter and less expensive over time. Naturally though we can’t reveal who it is.” As fuses and mechanically actuated switches would be too heavy or unreliable for professional UAVs, Xer’s PMU boards mount solid-state IGBTs, high-end units being selected to minimise thermal output, power inefficiencies and the amount of space they take up. By contrast, COTS batteries are integrated and are unmodified, given their relatively simple duties and the maturity of battery technology. While high C-rate modules are used to enable fast recharges from the alternator, they are otherwise standard. All this ensures stable power June/July 2022 | Uncrewed Systems Technology Payload and performance data can be streamed to the user’s GCS over 2.4 GHz, 4G or satcom links