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15 Unmanned Systems Technology | December/January 2018 Avid Technology has developed an axial- flux motor to provide higher power density and greater efficiency for UAS applications than conventional radial-flux permanent magnet motors (writes Rory Jackson). The design, for the Evo motor, enables the construction of a low-inertia rotor with speed adjustments in a timely fashion “It’s a different design from conventional motors,” said the company’s Ryan Maughan. “The UAV industry uses external rotors with permanent magnet motors – a radial-flux external rotor – whereas the Evo’s axial flux operates in a completely different direction to these.” The motor’s key feature is a carbon composite rotor, with the embedded magnet held by carbon fibre tape. This is bordered by two stators on either side of the rotor, and the Evo’s cooling mechanism for the stators enables the motor to be completely sealed. The system also has no external moving parts, giving UAS designers more flexibility in where it can be built into the airframe, as less space needs to be allocated to it. Wiring complexity is also reduced, as the electronics can be built into the motor. “A lot of UAVs opt for more and more motors and propellers because demands for increasing payload capacity require more and more lift,” Maughan added. “To stay manoeuvrable, however, they’re constrained in terms of the size of motor they can use, because of the inertia of the motor. That means designers have to keep adding motors.” Using sealed, axial-flux systems could reduce the overall number of rotors a UAV has to carry for a given payload capacity, and by extension reduce the complexity and maintenance requirements of the UAS as a whole. The Evo technology can also be scaled – current versions range from an 82 kg, 400 kW motor to a 22 kg, 85 kW motor. A 5 kW motor weighing less than 750 g is under development. Axial-flux motor advance Propulsion The key feature of Avid’s Evo motor is a carbon composite rotor Cloud Cap Technology is developing a new generation of its Piccolo autopilot with a modular architecture for autonomous coprocessor engines (writes Nick Flaherty). The architecture will also open up new ways of designing sensor systems for unmanned aircraft, according to Kevin Hunt, Piccolo programme manager at Cloud Cap’s owner UTC Aerospace Systems, in Oregon. The first step is a higher performance microcontroller and an Ethernet interface for faster data links, rather than the current UART interface. “If I take the Piccolo software into a higher performance platform with higher bandwidth, adding additional ‘outboard’ processing is straightforward,” Hunt said. That is a result of a well- established application coprocessing interface that allows third-party module software. “As a commercial off-the-shelf supplier, we would invite third parties to develop modules,” he added. “I am very interested in optical flow navigation in GPS-denied environments, optical sense and avoid, and using different varieties of Lidar and multi- spectral cameras [in the payload]. I’m looking at allowing those to also control the autopilot. “There are ‘unmanned’ systems now that require between one and 12 operators to keep them in the air, but I would far rather see an aircraft taking care of itself. That though requires greater degrees of contingency planning and understanding of what you need to do,” he said. “This year [2018] is where a lot of the foundational work will be happening to bring us to the next generation of systems, researching and porting to one or more hardware platforms. Autopilots focus, page 36 Airborne vehicles Autopilot has modular aim