Issue 41 Unmanned Systems Technology December/January 2022 PteroDynamics X-P4 l Sense & avoid l 4Front Robotics Cricket l Autonomous transport l NWFC-1500 fuel cell l DroneX report l OceanScout I Composites I DSEI 2021 report

PteroDynamics X-P4 | Dossier and more powerful links, along with pretty much any transponder systems end-users might want. It’s just a matter of being certain what they want, before going through the lengthy FCC licencing process to fly them.” Propulsion As indicated, the X-P4 features four propulsor nacelles, each of which contains a BLDC electric motor, an ESC and a lithium-ion battery pack with about 550 Wh of energy. Each nacelle has a battery panel (held in place by two screws) for removing and replacing the battery packs, although the team is looking at ways to recharge the plane without having to change the batteries. Various motor-propeller combinations have been trialled (and are kept on the engineering team’s racks) to identify ideal combinations of speed and torque for different mission requirements. Although T-Motor motors are used at the moment, the efficient air-cooling inherent in the propulsors’ design, and their modularity, means others can be used, providing they supply the power output necessary for all stages of flight. “The X-P4 uses about 7-8 kW to hover, and when we’re cruising at 65 knots or so the motors draw about 1.8 kW with fixed-pitch propellers,” Whitehand says. “If we’re dashing at 75 knots though, power consumption is about 2.5 kW, and naturally, when we’re transitioning, there’s a power curve that varies between the values for hover and cruise. For example, if we’re inbound, we can do a low-power extended flare approach, or if an end- user’s coming in hot and wants to do a quick stop, then obviously that’s going to be sharper and more power-intensive.” Petrov adds, “There is a slight trade- off here, in that we want to use powerful motors for take-off, hover and landing, but when we’re cruising we don’t really need high power at all. Switching to electric variable-pitch propellers in the future will not only boost prop efficiency, it will allow us to use less powerful motors during VTOL. It will also save on manufacturing and operating costs, which is why variable-pitch is a significant item on our roadmap. “Another area we’re looking into is small asynchronous motors. A lot of efficiency losses in permanent magnet BLDC motors come from the demagnetisation of their iron cores, so if we can have an asynchronous motor where we control the strength of the magnetic field, we could significantly improve efficiency in forward flight. “The only problem there is that, currently, no-one really makes three- phase AC induction motors at the right SWaP for our requirements, but it’s something we’re keeping an eye out for. “We’re also working with GM Propellers and Mejzlik on improving the performance of our current fixed-pitch propellers. » Robust Heading & Navigation in all conditions » Instant Initialization » Immune to Magnetic Disturbances NEW ELLIPSE-D www.sbg-systems.com 0.05° ATTITUDE POSITION 1 cm HEADING 0.02° The Smallest Dual Antenna & Dual Frequency INS with RTK