78 around the most common type of project that our engines get installed into nowadays – VTOL-transitioning, fixedwing UAVs with lift motors mounted on twin booms,” Bogdanov says. Upon startup, the engine drives the generator to charge dedicated lift batteries (a common feature in today’s hybrid-quadrotors), while the gearbox clutch prevents the RW1-300’s power getting sapped by the propeller. “Then, electrical output from the motor-generator is delivered via four controllers, each with four output channels, so 16 output channels in total. If more channels are desirable, we can just add more controllers,” Bogdanov says. “Each channel forms a 48 V connection, but they can be combined for 96 V, 144 V or 192 V connections, and so on, and the channels are assigned prioritisations to ensure some components keep receiving power, no matter what. For instance, the autopilot, flight surfaces and maybe the payload in some missions should never lose power. “But, some other systems, like ESCs [electronic speed controllers] for the lift motors, wing-mounted LEDs or some companion computers, aren’t critical to the UAV’s survival, and so they can be prioritised lower, so that if there’s something wrong with the engine or the system is overloaded, the ECU can cut the lower-priority groups to save the aircraft.” Engine management UAVHE’s ECUs are dual-redundant, featuring two identical PCBs, designed to comply with FAR 33 airworthiness standards, the company anticipating that future UAV engine regulations will be modelled around them. “To ensure those standards were met, the ECU was completely designed and built in-house, with every line of code coming from a blank sheet and not from any particular sort of open-source ECU software, and all industrial- or automotive-grade board components,” Bogdanov asserts. “All connectors and busbars were Amphenol mil-spec or aero-spec parts, while the main microcontroller is a fairly standard ARM chip. We run embedded software on that in two layers: one is our RTOS for the core functions of engine performance, and the other is more of an application layer, with a Unix OS running system health monitoring, statistics, data logging and networkrelated tasks, like controlling the CAN and Ethernet buses around the engine that the sensors, fuel injection, ignition and supercharger rely on.” Bogdanov notes that running two layers of ECU software on a single chip is rare, but this is primarily due to automotive rules made in the 1980s, designed to prevent overloading the far lower-power chips of that time. These days, chips are far more powerful and capable than most regulating bodies realise, to the point that fuel, air and electricity mappings about the engine and generator can be recalculated at least once, sometimes twice, per shaft revolution. The ECU is designed with inputs for tracking the level, pressure, flow, temperature and viscosity of the fuel, and to have multiple of each sensor placed at different points along the April/May 2024 | Uncrewed Systems Technology Dossier | UAVHE RW1 rotary UAVHE’s production machines include 5-axis and 9-axis CNC milling machines from DMG MORI, CNC metal cutters from Haas, and laser etching machines The ECU was completely designed and built in-house, with every line of code coming from a blank sheet and not from any opensource ECU software
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