Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

70 Dossier | HFE International GenPod optimal power and rpm for running it according to different mission factors. These include the altitude, desired engine power and electrical power being produced by the generator (accounting for the latter’s parasitic effects on propeller power and torque). The tables for those are provided as guidance in the GenPod’s product manual. “In addition to Mejzlik having been key there, we also work with Skybridge, a company on the US East Coast that does all our propeller characterisations, including modelling and sizing,” West says. “The sizing of our propeller is key to achieving the highest possible revs and power from the engine.” Health and data monitoring As mentioned, the GenPod carries a data logger. It can record 300 hours of data, and when it reaches that limit, the system continues by writing over the earliest data already recorded. The data is taken via CAN from the ECU, and in future it will also be transmitted in real time to the operator at the GCS via a 3G IoT modem and HFE’s cloud server. At the time of writing, only error codes were being transmitted, to save on bandwidth. HFE has developed its range of error codes and corresponding alerts to display detected or potential engine failures on a side-screen or at the user’s interface. If there are no errors, the screen can be set to display the engine rpm or operating hours logged; however, the 3G device can be removed or omitted at the point of purchasing a GenPod if an end- user prefers not to transmit engine data over the cloud. West adds, “Our software engineers have attached prioritisation levels to each error code, so if more than one issue is found, the most threatening one is displayed on top. “Much of the error code development work has focused on the crank sensors, since it’s important to identify what a problem there can mean. If a crank sensor fails, a wire might be broken, and you might see spikes or drops in rpm without realising that those readings are coming from a failed connection. “We spent a lot of time looking into how those failures are manifested to correctly diagnose what the problem is based on the patterns and ranges in crank sensor data.” Future plans The scalability of the GenPod is such that HFE is now working on further versions of it. These will incorporate Desert Aircraft’s larger engines, as well as hybridisation for users looking for optimised energy efficiency. August/September 2021 | Unmanned Systems Technology GenPod 100 Engine base: DA-100 Engine type: gasoline, spark- ignited, twin-cylinder boxer Displacement: 100 cc Maximum peak power: 6.1 kW (at 9000 rpm) Maximum continuous power: 5.5 kW (at 7000 rpm) Peak torque: 7.7 Nm (at 6500 rpm) Maximum torsional impulse: 16 Nm BSFC in cruise mode: 564 g/kWh (at 6500 rpm) BSFC at idle: 825 g/kWh (at 2500 rpm) Maximum peak speed: 9000 rpm Maximum operating speed: 7500 rpm Standard operating rpm range: 2500-7000 rpm Full system weight (including mufflers): 5.54 kg Full system power-to-weight ratio: 1.1 kW/kg Nominal current draw: 0.5 A (at 12 V) Maximum current draw: 1 A (at 12 V) Rated maximum cylinder head temperature: 130 C Minimum rated ambient operating temperature: -18 C Maximum rated ambient operating temperature: 49 C Nominal dynamic compression: 9 bar Compression ratio: 8.5:1 TBO: 300 hours Some key suppliers Servos: Volz Servos Fuel couplings: Battlefield International Engines: Desert Aircraft ECU: In-house Wire harnesses and connectors: Amphenol Wire harnesses and connectors: Omnetics Plastic parts: Stratasys Vibration mounts: Lord Generator and power management unit: Acutronic Power Systems (formerly Sullivan UV) Decompression valves: Acutronic Power Systems Mufflers: Cobra Mufflers: Slimline Acoustic simulations and validations: SidLab Fuel lines: Festo Propellers: Mejzlik Specifications