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Programmed multicopter flies through the Arctic autonomously

November 17, 2015  - By
Researchers conducted an autonomous multicopter flight in the Arctic with its own test UAV platform that used a u-blox LEA-M8T GPS receiver. (Photo: Alfred-Wegener Institute)

Researchers conducted an autonomous multicopter flight in the Arctic with its own test UAV platform that used a u-blox LEA-M8T GPS receiver. (Photo: Alfred-Wegener Institute)

How do you successfully pilot a UAV in the remote expanses of the Arctic Ocean when the compass can’t provide reliable positioning data? Engineers on board the Alfred Wegener Institute’s (AWI’s) research icebreaker Polarstern specially programmed a multicopter, allowing it to navigate despite the deviations produced by the Earth’s magnetic field near the North Pole. The researchers recently celebrated the copter’s first successful autonomous flight and landing on an ice floe.

“At high latitudes, autonomous navigation is a major challenge,” said Sascha Lehmenhecker, an engineer at AWI. “Navigation systems normally use magnetic sensors. But near the poles, the lines of the Earth’s magnetic field are nearly perpendicular to the ground, making precise navigation extremely difficult. That’s why commercial multicopter control systems aren’t well suited for use in polar regions.”

Ice Floe Landings

Lehmenhecker’s team refined the control systems for multicopters to land on ice floes and fly back to their “mother ship” autonomously several hours later. The particular task: both the ice floe and the ship are in motion. The ship has to continue on its scheduled course to conduct other research, while wind, waves and currents cause the ice floe to drift. It’s precisely the direction and speed with which it drifts that the multicopter needs to determine.

The team pursued two approaches. “In the first approach, the multicopter remains in constant contact with a receiving station, which uses the copter’s GPS data to calculate the discrepancies. In other words, the multicopter transmits its GPS position to the station, which in turn transmits back the corresponding, adjusted coordinates,” explained Lehmenhecker. “The second option: We use two onboard GPS receivers to calculate the actual change in the copter’s position. Though this is the better method, it’s also much more complex, and we’re still just starting to develop it.”

The system passed its first test, conducted on an ice floe in the arctic Fram Strait (79° N parallel). In the test, the team and copter were left on a floe, clear of magnetic interference produced by electric motors on board the Polarstern. The team manually flew the copter 3 kilometers out, to the edge of visual range, then activated the autonomous return program. The multicopter flew to the preset coordinates and safely landed on its own.

Underwater Assist

Lehmenhecker’s team came up with the idea for this development in connection with the use of sensitive devices under the ice, such as the torpedo-shaped autonomous underwater vehicle (AUV) Paul, which explores the ocean beneath the sea ice. “To optimally plan its dives, it’s important to have precise information on the movement of the sea ice,” Lehmenhecker said. Conventionally, this was achieved by deploying ice trackers on floes with the help of a Zodiac boat or helicopter  — a difficult and time-consuming method. Further, the researchers generally try to avoid leaving the safety of the Polarstern wherever possible — jagged ice floes and polar bears present additional risks.

During 2012, the group first used a UAV to assist Paul. The UAV landed on the ice via remote control, then used GPS to determine its position and transmit the data back to the research ship, which was monitoring Paul’s dive. In this way, the multicopter took on an important role, offering navigational support for the AUV. Once each dive was complete, the ship had to return close to the multicopter’s position so the pilot could remotely guide it back to the ship, which was only possible in visual range.

Now, the new developments “will expand the service radius of our copters from visual range to as much as 10 kilometers,” Lehmenhecker said.

This is posted in From the Magazine, UAV/UGV