Unmanned Systems Technology 021 | Robot Aviation FX450 l Imaging Sensors focus l UAVs Insight l Liquid-Piston X-Mini l Riptide l Eurosatory 2018 show report l Zipline l Electric Motors focus l ASTS show report

VTOL transition to take off using eight electric motors and fly horizontally with one nose-mounted pull-rotor at 112 kph (rather than be limited to the speeds of multi-copter based designs for unmanned agricultural spraying, such as the DJI Agras MG-1, which has a maximum operating speed of 28.8 kph). The craft has also been designed with a relatively large scale in mind, to carry up to 15 kg of chemical fertiliser or pesticide, for a total MTOW of 35 kg. Applying agricultural chemicals at or above industry standards for dispersion quality and efficiency was another key target. “Present-day applications can be about 20-30 gallons per acre, but with droplets of 400 microns to ensure an even spread of chemicals,” Surdu says. “The Kray Protection UAV’s rotary atomisers produce droplets from 20- 150 microns in diameter, and ensure a standard deviation of no more than 10- 15% from the mean size by spinning at 40,000 rpm.” The company has also designed and patented a peristaltic pump, to maintain a precise flow rate of spray fluid while preventing the liquid from making contact with the chemical delivery system’s moving mechanisms, which can cause corrosion over time in aerial spray vehicles. “This was also critical for reducing the weight of solution carried aboard the UAV, and to make sure the CoG remained stable,” Surdu says. UAV development continues to pose a balancing act involving a range of hardware, programming, electronics and aerodynamics. Even without platforms becoming scaled down, the rapid rate of advances in computer technologies, materials and power systems puts pressure on UAV designers to optimise every aspect of a system. With the vast supply of vehicle manufacturers in the industry, however, markets could well be captured not by maximising performance and efficiency but by the combined convenience and urgency of missions the UAVs are poised to perform.