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62 making it quite light. It gives an additional layer of protection to the avionics and engine against adverse weather, even though those are mostly already enclosed, and the canopy has a quick opening system to enable fast access to internal parts of the aircraft.” Autonomy and control systems The UAV’s autopilot is based on Ardupilot, for the versatility this open- source software typically lends itself to; the company also contributes to the Ardupilot project. Cortes adds, “Our flight controller’s hardware is enclosed in a ruggedised aluminium case, and uses Micro D-Sub connectors based on the MIL-DTL-32139 standard. Those parts are necessary to provide a high level of reliability compared to similar unmanned solutions, and to further protect the main computer against engine and motor vibration.” Using Ardupilot has allowed the development team to integrate all their components natively, such as the aforementioned governor and an EFI control system, so that they (and end-users) can monitor these systems from a GCS. “The governor and EFI are collectively in charge of the hybrid power system’s various functions,” Fuentes says. “Engine throttle management is based on the load demanded from the battery, and that is sensed using a voltage tracker on the battery and current sensors measuring at the motors and the generator.” The EFI’s control algorithm is based on an Alpha-N tuning strategy, using data inputs from sensors measuring absolute (barometric) pressure, intake air temperature and cylinder head temperature. “We have simplified the EFI as much as we could, with our own patented technology that removes the TPS [throttle position sensor] and the mechanical pressure regulator,” Cortes says. “That makes the system much lighter while maintaining the same level of performance. “The EFI adjusts itself to the conditions of altitude and temperature, replacing the need to manually adjust the needles of a carburettor – an issue many customers have had with small hybrid-electric craft, and which can lead to a potential failure of the power system if executed wrongly.” As mentioned, the use of Ardupilot has also enabled continued compatibility with other mission-critical third-party technologies, such as Lidars, multi- sensor gimbals and other payload sensors and accessories. Future developments As has been discussed in previous issues of this magazine, many UAVs in Europe are designed with MTOWs limited to 25 kg to comply with current aviation regulations on UAS weight limits, and the HYBRiX 2.1’s heavy-lift version will be no exception. “We hope to modify and enlarge our craft to expand its capabilities further in the future, however, when new European regulations enable greater MTOWs,” Fuentes says. “We are also looking to design and develop an emergency flight termination system, which would include a parachute. The planned FOC motor control system will play into that, as we will need to stop the electric lift motors very rapidly and at short notice if we need to halt the HYBRiX in its tracks and release its parachute.” April/May 2020 | Unmanned Systems Technology Digest | Quaternium HYBRiX 2.1 Dimensions: 1249.29 x 509.34 mm MTOW: 20 kg Engine: Two-stroke, 32 cc, single-cylinder Maximum endurance: 4 hours Maximum speed: 80 kph Payload capacity: 5 kg Some key suppliers Engine: Zenoah Engine management systems: in-house Electric motors: MAD Components Generator: in-house Exhaust: in-house Propellers: T-Motor Motor control: Texas Instruments Flight controller: in-house Autopilot: Ardupilot Specifications A future version of the HYBRiX will be able to carry 10 kg on a 25 kg MTOW, enabling a wider range of heavy-lift applications such as last-mile delivery or agricultural spraying