Unmanned Systems Technology 019 | Navya Autonom Cab | Batteries | UGVs Insight | UAV Factory UAV28-EFI | Swiss Aerobotics Hummel | UMEX 2018 report | Antennas | Oceanology International 2018 report

62 Fuel injection development Since UAV Factory does not supply to customers who have a ‘heavy’ fuel requirement it has not had to develop its engine to run on such fuel. Nevertheless, Popiks admits that development of a reliable fuel-injected version of the engine was particularly challenging. The company initially worked with a supplier of a port injection system that replaced the carburettor with which it had begun engine development. However, Popiks reports that it became necessary to develop an in- house system to obtain the level of performance and reliability it required at a more reasonable cost. The UAV Factory port injection system embraces its own ECU. This uses an automotive processor together with UAV Factory’s own printed circuit board (PCB), within an aluminium housing. Popiks says, “We use an automotive processor but we designed the PCB ourselves because an automotive PCB contains a lot of items that are not relevant to our requirements.” UAV Factory writes its own software, and designs and manufactures its PCBs in-house. The ECU operates both the injector and the ignition via integrated drivers, the throttle via a servo, the cooling flap via a servo and the electric fuel pump. Since it controls the throttle there is no need for a load sensor, and key inputs are a Hall effect sensor for crankshaft position/speed, manifold air temperature and pressure, and cylinder head temperature sensors. In addition, an ambient air pressure sensor is integrated into the ECU. The manifold pressure sensor is the primary input to the map determining injection timing, and the ECU adjusts the mixture according to altitude as identified by ambient air pressure. The in-house development of fuel injection is claimed to have improved fuel efficiency by 30% over the original carburettor version of the engine, and with a major improvement in reliability. Popiks notes, “Significant effort has been put into subjecting the electronics, including the ECU, to a highly accelerated lifetime testing – ‘HALT’ – programme. We developed the ability to do this in-house, including the use of a six-axis vibration rig and temperature testing from -100 to +200 C. That was important as it directly affects the robustness of the system, and it led to us making changes that further improved the MTBF.” The ECU has onboard data acquisition using an 8 Gbyte flash card plus telemetry. Data is collected from various additional sensors including ignition current, injector current, throttle servo current, fuel pump current and so on. All this data is logged while the monitoring software sends the data in real time back to the ground station. At the ground station the software displays visual bar indicators of all critical engine parameters. A colour indication gives an operator a clear overview of the system status, and allows troubleshooting of potential issues during the flight. “Normally symptoms start to occur before a failure occurs, so if you can figure those out there is the potential to save the aircraft,” says Popiks. “The analysis is carried out automatically by the software in the base station on the ground,” he explains. “The operator there sees the data and can take the final decision as to what to do. “Some of the analysis is done at the base station, and some on the vehicle. For example, the ECU can determine if there is a pre-ignition condition – which would have to be due to incorrect maintenance, as under normal operation the engine isn’t prone to it – and can immediately take April/May 2018 | Unmanned Systems Technology Dossier | UAV Factory UAV28-EFI The UAV28-EFI has port injection run by UAV Factory’s own engine control unit Some analysis is done at the base station, some on the vehicle. For example, the ECU can determine if there is pre-ignition