Swifts Provide Inspiration for Lightweight, Quiet, and Maneuverable Ornithopter Drone
Inspired by biology, the swift-based ornithopter has its quadcopter competition beaten on noise and agility — and needs less power, too.
Researchers from Nanyang Technological University, the Defense Science and Technology Group, Qingdao University of Technology, the University of South Australia, and National Chiao Tung University have released a paper detailing an ultra-lightweight ornithopter drone — which flies, far more quietly than a quadcopter, by flapping its wings.
"The aerobatic maneuvers of swifts could be very useful for micro aerial vehicle missions," the team explains in the paper's abstract. "Rapid arrests and turns would allow flight in cluttered and unstructured spaces. However, these decelerating aerobatic maneuvers have been difficult to demonstrate in flapping wing craft to date because of limited thrust and control authority. Here, we report a 26-gram X-wing ornithopter of 200-millimeter fuselage length capable of multimodal flight. Using tail elevation and high thrust, the ornithopter was piloted to hover, fly fast forward (dart), turn aerobatically, and dive with smooth transitions."
"There are existing ornithopters that can fly forward and backward as well as circling and gliding, but until now, they haven't been able to hover or climb," says professor Javaan Chahl of the team's work. "We have overcome these issues with our prototype, achieving the same thrust generated by a propeller.
"The triple roles of flapping wings for propulsion, lift and drag enable us to replicate the flight patterns of aggressive birds by simple tail control. Essentially, the ornithopter drone is a combination of a paraglider, aeroplane and helicopter."
"Unlike common quadcopters that are quite intrusive and not very agile, biologically-inspired drones could be used very successfully in a range of environments," explains project lead Dr. Yao-Wei Chin. "The light weight and the slow beating wings of the ornithopter poses less danger to the public than quadcopter drones in the event of a crash and given sufficient thrust and power banks it could be modified to carry different payloads depending on what is required."
The compact ornithopter is not only quieter and more agile than a propeller-driven drone of the same size, but more power-efficient. "We developed a low-loss anti-whirl transmission that maximized thrust output by the flapping wings to 40 grams in excess of body weight," the team explains. "By reducing the reactive load and whirl, this indirect drive consumed 40% less maximum electrical power for the same thrust generation than direct drive of a propeller."
The paper has been published under closed-access terms in the journal Science Robotics. You can also read more about the project in Chahl's The Conversation article.