Unmanned Systems Technology 013 | AutonomouStuff Lincoln MKZ | AI systems | Unmanned Underwater Vehicles | Cosworth AG2 UAV twin | AceCore Neo | Maintenance | IDEX 2017 Show report

66 separately mounted electronic speed controller (ESC), also from Kontronik. The ESCs are clamped in place and connected to the motors and the battery pack using silver connectors; silver has the highest electrical and thermal conductivity of any metal. The motors are fixed with screws to a CNC-machined 7075 aluminium alloy mounting plate moulded into the end of each arm. Adapters also made from 7075 aluminium secure each propeller to its motor. The propellers themselves are also made from carbon fibre-reinforced plastic, in the form of spread-tow tape from TeXtreme, which is also used in Formula One cars and racing motorbikes for example. The tape, according to TeXtreme, is much thinner than conventional carbon fibre tapes and packs the material more densely for greater mechanical performance. Groenendaal adds that spread- tow material also minimises voids in components by ensuring more even distribution of the fibres across the width of the tow. Starting with a standard propeller from their partner’s range, whose diameter is limited by airframe clearance, AceCore worked with the company through a process of trial and error to optimise parameters such as the aerofoil shape, and the twist and pitch of the blades, to produce a customised solution. The motors and propellers are mounted with a 5° offset, a detail that emerged as a solution to a stability problem in descent that was revealed in flight testing. At certain combinations of forward speed and descent rate, the vehicle was descending into its own turbulent rotor wash. The 5° outward cant pushes this air out and away from the vehicle, allowing it to descend into smoother air. Power comes from a pair of 22.2 V lithium-polymer batteries in 6S format, chosen because it is in common use in equipment used by the film and TV industry. While AceCore recommends batteries from Gens Ace, other brands can be used, although Groenendaal advises customers to ensure that any batteries they use can handle high currents. “When the maximum take-off weight is used and the Neo is ascending fast, there is a lot of current draw,” he says. The batteries are connected in parallel, a detail that fits with AceCore’s policy of safety through redundancy because it means full power will be available even if one of the batteries fails completely, although endurance will effectively be halved. A carbon fibre dome protects them from rain. Power distribution To get the power to the motors and the other electrical loads – including the ESCs, the flight control computer, the radio link and the landing gear servos – AceCore has developed its own bespoke power distribution board. This not only ensures a good physical fit into the vehicle’s unique shape, but also that the conductive paths and the connections can handle the high currents involved and the associated heat loadings. All the loads are connected directly to the batteries via this distribution board and, where necessary, include integral power conditioning electronics, so the whole vehicle runs on dc power. The flight controller, for example, comes with its own power control system, while the chips in the ESCs are set up so that the dc power supply is acceptable, Groenendaal notes. The landing gear servos are industrial-grade Futaba items that are used to swing the Neo’s carbon fibre legs and feet up and out of the way April/May 2017 | Unmanned Systems Technology AceCore offers an RTK kit with two antennas for centimetric accuracy, and a triple-redundancy kit with three GPS receivers and three IMUs Sophisticated features do not figure high up in the hierarchy of needs in a flight controller for film work, but reliability does