A researcher from the University of Sydney has designed and tested a method for autonomously docking unmanned aerial vehicles (UAVs) to enable refueling or recharging in mid-air.

UAVs to dock and recharge in mid-air. Image Credit: Daniel Wilson"At the moment, a UAV's range and endurance is constrained by the amount of fuel that can be stored on board," says Daniel Wilson, whose research addressed the limited endurance levels of unmanned aerial vehicles. “As you add more fuel, the weight of the aircraft increases, which means more fuel must be consumed to stay aloft."

Wilson works at the University's Australian Center for Field Robotics and Marulan air strip, and used a combination of measurements from an infrared camera and GPS to enable the in-flight docking to occur.

Wilson says there are two autonomous aircraft, a leader and a follower. The leader tows a cone-shaped, parachute-like drogue. The objective is for the follower to autonomously dock its nose within the drogue.

Initially, both aircraft rendezvous to a formation position where the follower's infrared camera can observe infrared LED markers on the leader's wingtips and tail. Once it docks, the follower is commanded to station for a certain amount of time to simulate refueling or recharging. The follower disconnects and resumes its mission.

“The biggest challenge is the highly accurate and reliable relative positioning performance to allow a second aircraft to dock with a small target, in the air, and amidst turbulence," Wilson says.

“It would allow aircraft to use their fuel to search the target area, rather than flying back and forth from land," he adds. “It could also be used to keep high-flying UAVs airborne, in place of satellites for communication."