Unmanned Systems Technology 020 | Alpha 800 I Additive Manufacturing focus I USVs insight I Pegasus GE70 I GuardBot I AUVSI Xponential 2018 show report I Solar Power focus I CUAV Expo Europe 2018 show report

53 an alternative technology, one inspired by my brother’s knowledge of series hybrid powertrains for ships,” McRoberts says. The concept was to power the propulsion motors directly from an ICE- driven electrical generator. The main drawback of applying that approach to a UAV was the variation in power demand through the course of a flight; a means had to be found to overcome that. “To produce a workable and scalable system we had to go back to the drawing board,” McRoberts recalls. That was in late 2015, which is when Pegasus Aeronautics was established by the three graduates in Waterloo. “It was then a two-and-a-half-year development process to get where we are today with a system that has flown and has worked really well, and is fully scalable and straightforward to implement in any existing UAV,” he says. Funding for the development process came from the Canadian Government. “As of a couple of months ago we received a very significant investment from a private investment group that had researched the entire field of hybrid systems for UAVs, and had decided that we are going in the right direction,” McRoberts says. “We don’t know of any competitor using the same approach as us.” Essence of the system The Pegasus GE70 system marries a gasoline port injected, spark ignited, conventionally throttled two-stroke ICE to an AC generator. The drive for the generator’s rotor is the only output from the ICE’s crankshaft, and the coupling is permanent such that the generator always runs at engine speed. It powers the UAV’s electric motors in place of the regular battery pack. There is full electronic control of the ICE’s throttle, injection and ignition, allowing for manipulation of its torque output. It follows that a given level of shaft power (below peak) can be obtained over a range of engine operating speeds. At the same time, there is full electronic control of the generator, via a generator control unit (GCU), which rectifies its AC output to the DC current required by the UAV. The GCU incorporates the ECU governing the operation of the ICE. Since the ICE can provide a given Pegasus GE70 | Dossier Unmanned Systems Technology | June/July 2018 At the 2018 Xponential show in Denver, Colorado (May 1-3), Pegasus Aeronautics demonstrated its GE70 system installed in this Dragonfly multi-rotor UAV from Aerial Alchemy. The vehicle in this form weighs 13.5 kg dry, and its six rotors each have a 27.5 in span. The general arrangement of the vehicle allows for a long ‘tuned’ exhaust pipe. The fuel and coolant pumps are tucked in underneath while the radiator is mounted between the rear pair of rotors. The underslung fuel tank straddling the centre of the craft has a 7.0 litre capacity, which should be enough for more than 90 minutes of operation when the Dragonfly is carrying a 5 kg payload Note that in Aerial Alchemy’s Dragonfly the GE70 engine/generator unit is mounted underslung and upside down, which is made possible by the use of fuel injection rather than a carburettor