Transforming Drone Floats Like a Helicopter and Cruises Like a Plane

U-Lion's three flying modes. (Image courtesy of Science China Press.)

Two PhD students from the National University of Singapore’s Unmanned System Research Group spent four years in developing a novel hybrid unmanned aerial vehicle (UAV) called U-Lion. U-Lion can take-off and land vertically like a helicopter and transition to cruise flight like an airplane.

The wings can be fully retracted or expanded, to favor stability in VTOL mode or provide efficient lift in cruise flight. U-Lion is also able to fly and transform autonomously.

Their research has been published in Science China Information Sciences.

In recent years, hybrid UAVs have attracted worldwide interest for their potential applications in military and civilian operations, especially where there are severe constraints in the operating environment, such as sea surveillance or forest mapping. A hybrid’s VTOL capability minimizes its dependency on takeoff and landing facilities while its cruise flying capability allows it to perform long range and long duration tasks. Many companies have devoted resources to developing hybrid UAVs, such as Google’s Project Wing.

However, due to the structural differences between VTOL UAVs and fixed-wing UAVs, combining the two functionalities into a single UAV is a challenge. In addition, due to the high uncertain aerodynamic forces in the transition process, the transition process is difficult to automate. Consequently previous attempts of hybrid UAVs tended to focus on optimizing one of the flying modes, but not both.

To achieve optimal performance in both flying modes, U-Lion is designed with a tail-sitter configuration, with reconfigurable wings and vectoring thrust. U-Lion can adopt different flying modes based on the mission requirements, adjusting its wings automatically to achieve optimal performance.

This allows U-Lion to fly much longer than typical VTOL UAVs and possess greater maneuverability compared to normal fixed wing UAVs. The researchers developed special modelling and control algorithms in order to overcoming the uncertainties in transition and achieve autonomous full envelope flight.

"U-Lion, the autonomous hybrid UAV, has great potentials in many applications," said PhD student Wang Kangli. "The VTOL capability has widened its application environment and cruise capability enables it to perform long range tasks. The autonomous capability relieves the dependency of experience pilots and further expands its applications."

"Being optimal in both flying modes, U-Lion may bring a new way for people to operate drones, said PhD student Ke Yijie. “The fast reaction and static hovering capabilities give U-Lion great potential in many applications and the VTOL capability allows it to operate in almost anywhere, including on vehicles on the sea."

“In five to ten years' time, hybrid UAVs will change the way people operate in areas like forest mapping, sea surveillance, power line inspection and disaster reaction,” Ke Yijie added.

For more UAV news, check out DroneClash: the world’s first drone demolition derby.

Source: Science China Press