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

61 Pegasus GE70 | Dossier customer might come to us and say they like the diagnostic capability but want to be able to interface with it better, given that they are using such- and-such protocols, so they want such- and-such a module in our software to be reprogrammed. That is completely possible given the microprocessors we have selected.” GE70 battery The system battery is dwarfed by those the GE70 is replacing. McRoberts explains, “If there is a huge transient load – say the vehicle is hovering and all of a sudden it is hit by a gust of wind – inherently the power response from the ICE is insufficient to deal with a scenario like that. “You need to vector power to the appropriate places such that the platform can remain stable. That is where the battery comes in as a supplementary power source, and it is in this mode that the system’s peak power can be reached. “That is why we want the battery to be charged at all times. We ensure it is charged and discharged within its limits and in a way that the platform can remain stable. “In a charging event we can choose the rate at which it is recharged [via the EGU] so that it remains within its limits. We also monitor the voltage of the battery and so on to ensure it is in good health. “The system has the ICE directly powering the UAV 99% of the time. The beauty of that, first and foremost, is you are not cycling a battery repetitively, which shortens its life. And in an absolute sense the improvements in efficiency are there if you aren’t constantly charging or discharging a battery.” Do you start with a fully charged battery to fire the engine? “Generally speaking, it doesn’t matter how high the charge is for fire-up, but once the generator is running it will do everything necessary to maintain it at its storage state,” McRoberts says. “Basically that is the state at which the battery has the highest longevity. If you are doing aggressive flight manoeuvres, as soon as those stop then the generator will recharge the battery. “The other thing to note is that if those aggressive manoeuvres are occurring consistently and the power level isn’t changing that much, the generator may output the power necessary for them unaided. It is only huge step-loads where the battery might be called on to kick in. “The control we have over the battery means we can improve the overall efficiency of the system, and that its use can be minimised to ensure it lasts a long time.” GE70 operation McRoberts emphasises, “Essentially you take out the standard battery pack and replace it with the Pegasus system, retaining the standard electric motors and motor controllers. To all intents and purposes, the UAV cannot tell the difference when using our system. “The aim behind the way we devised the system is that the user doesn’t need to care how the system works. The UAV needs a given amount of power, and the system can match that demand.” Of the operation of the Pegasus control system, McRoberts says, “This could be described as an ‘electrical CVT’. Picture a car on a highway. It could drive at 90 kph in a low gear spinning at a high rpm, but then the BSFC is much higher. If the vehicle has a CVT, the gear ratio will change mechanically such that the engine is producing more torque at a lower rpm so that the vehicle runs more efficiently. “To a large degree, that is the Unmanned Systems Technology | June/July 2018 The GE35 single-cylinder engine/generator unit