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Sydney researcher designs and tests new method to refuel UAVs in mid-flight

Unmanned aerial vehicles or UAVs can now be refuelled in mid-air, thanks to a study by University of Sydney researcher, Daniel Wilson.

Daniel has designed and successfully tested a new method for autonomously docking drones to refuel or recharge mid-flight. His PhD research addressed the limited endurance levels of unmanned aerial vehicles.

According to Daniel, a typical UAV’s range and endurance are constrained by the amount of fuel that can be stored on board. Adding more fuel will only increase the weight of the aircraft, which will require more fuel simply to stay aloft.

Working at the University’s Australian Centre for Field Robotics and the Marulan airstrip, Daniel used a combination of precise measurements from an infrared camera, with GPS and inertial sensors to allow the sky-high docking to take place.

Aerial refuelling, though common in manned aircraft, had not been demonstrated in airborne UAVs until Daniel’s experiments late last year. He explains that the biggest challenge is the highly accurate and reliable relative positioning performance required to allow a second aircraft to dock with a small target, in the air, and amidst turbulence.

Daniel says that his new technology will be useful in situations where greatly extended persistence over an area is desirable, such as the ongoing search for the MH370. With this capability, the UAV can carry out extended searches over the target area instead of having to fly back and forth from land. It could also be used to keep high-flying UAVs airborne in place of satellites for communication.

Daniel has developed an autopilot and rapid software development process, which twice won him the International Simulink Design Challenge.

Daniel’s airborne docking design consists of two autonomous aircraft, a leader and a follower. The leader tows a cone-shaped, parachute-like drogue, and the objective for the follower is to autonomously dock its nose within the drogue.

Once docked, the follower is commanded to station for a certain amount of time to simulate refuelling or recharging. The follower then disconnects and resumes its mission.

The complete results of Daniel’s 4-year research project co-supervised by Professor Salah Sukkarieh and Dr Ali Gӧktoğan will be described in his PhD thesis ‘Guidance, Navigation and Control for UAV Close Formation Flight and Airborne Docking’ scheduled for publication later this year.

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