Researchers develop hybrid UAV that offers multiple flight modes

It’s not just your typical unmanned aerial vehicle (UAV). Two PhD students from the National University of Singapore, Unmanned System Research Group have spent the last four years developing a unique hybrid UAV that offers multiple flight modes.

Hybrid UAV U-Lion with three flying modes. ©Science China Press

Dubbed U-Lion, this hybrid UAV can take-off and land vertically, much like a helicopter, but in transit, the vehicle flies horizontally, much like an airplane.

The wings can be fully retracted or expended, to favor the stability in VTOL mode or provide efficient lift in cruise flight. U-Lion is also able to operate autonomously, including during vertical take-off and landing, cruise flight and autonomous transitions.

The VTOL capability minimizes the dependency of the take-off and landing facilities and cruise flying capability allows hybrid UAVs to perform long range and duration tasks.

The research team, with work mainly conducted by Wang Kangli, Ke Yijie under the supervision of Professor Chen, overcame some significant design challenges, including combining the vastly different functionalities of VTOL and fixed-wing UAVs into one vehicle. For the most part, research has focused on only one of the two flying modes, rather than optimizing both capabilities. Due to the highly uncertain aerodynamic forces in the transition process, this has been difficult to automate.

To deal with this problem, the researchers designed U-Lion to include a tail-sitter configurations with reconfigurable wings and vectoring thrust. U-Lion could adopt different flying modes based on the mission requirements, and adjust the wings to achieve optimal performance. The ability allows U-Lion to fly much longer than typical VTOL UAVs and possess greater maneuverability compared to normal fixed wing UAVs. Advanced modelling and control algorithm is also developed for overcoming the uncertainties in transition and achieve autonomous full envelope flight.

“U-Lion, the autonomous hybrid UAV, has great potentials in many applications.” Said Kangli, “The VTOL capability has widened its application environment and cruise capability enables it to performance 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 people operates drones. The fast reaction and static hovering capabilities bring U-Lion great potential in many applications, the VTOL capability allows it to operate in almost anywhere, including on vehicles on the sea.” Said Ke Yijie, “In five to ten years’ time, hybrid UAV will change the way people operate in areas like forest mapping, sea surveillance, power line inspection and disaster reaction.”

The research has been published in in Science China Information Sciences, Volume 60, Issue 3, 2017.