From fluttering bird wing to flapping drone

Knowledge of the aerodynamics of avian wings at low speeds has helped William Thielicke to design a drone (air reconnaissance) that flaps like a bird. It is ideal for covering long distances before flying slowly through a collapsed house, for example, in search of survivors. Thielicke, who has won several competitions for self-built multicopters, will be awarded a PhD by the University of Groningen on 31 October.

William Thielicke is inspired by nature. He studies living beings to find out how they solve the technical problems posed by nature. Flying is a prime example. People have been studying birds for hundreds of years in an attempt to reproduce their natural skills.

In addition to his academic work, since 2007 Thielicke’s hobby has been designing and building multicopters (helicopters with more than one rotor), which he controls via a video link as if he were sitting in the cockpit. ‘I build all the hardware and software myself.’ He enters his multicopters in international competitions that test their speed, manoeuvrability or both, and now has a cupboard full of prizes and a reputation as one of the best model multicopter pilots in Europe.

Hovering

The first step in Thielicke’s PhD research was to study the way that birds fly slowly. ‘We already know a lot about how birds fly fast, but birds can also hover, hanging in the air without appearing to move. The models we use to describe normal flight don’t work for this skill.’

During his Master’s research project, Thielicke saw similarities between the aerodynamics of slow-flying birds and insect flight. This has since been confirmed by other researchers. ‘Insects use a downwards movement to create vortices above their wings. These ‘leading edge vortices’ lower the pressure above the wings, thereby creating extra lift’, explains Thielicke.

He examined a model wing (based on a swallow’s wing) in a wind tunnel. A special scanning system was used to gather data for generating a 3D image of the flapping wing and the air flows during the entire wing flap cycle. The study showed that the thicker ‘upper arm’ of a bird’s wing works in much the same way as a conventional aircraft wing, where a difference in the speed of the air flow above and below the wing is used to generate the lift.

Disaster response

The thinner end (the ‘forearm’) is the part that works like an insect wing. Every downward movement creates vortices above the wing, which lower the pressure and give the bird extra lift, as it were. This part of the wing is responsible for most of the ‘lift’ at slower speeds. The 3D scans also showed the importance of the angle at which the wing moves.

The combination of efficient, fast flight and the ability to hover in the air is ideal for air reconnaissance above disaster areas, for example. ‘First, you have to be able to reach the disaster area, and having got there, you must be able to carry out a thorough search. A remote controlled aircraft is capable of the first part but not the second, and helicopters aren’t built to cover long distances’, says Thielicke. His calculations show that an aircraft that flaps its wings like a bird combines the benefits of both models.

Military training village

He recently took part in a major international competition organized by TU Delft, in which he competed against professional teams from Asia. ‘We had to act out a scene in a military training village. The participants were given thirty minutes to localize and search a house, identify various objects inside it and a few other similar tasks.’ Thielicke entered with his own hexacopter (with six rotors) and won second prize.

Toy manufacturer

Thielicke has now turned his hobby into his profession: after finishing his PhD research he started working for the toy manufacturer Tobyrich, where he designs remote-controlled multicopters. And a Swiss company has taken one of his earlier models into production. ‘Until a couple of years ago, I did everything through open source and shared my ideas with a lively community of like-minded people, who thought along with me. But there are now plenty of ready-made models in the shops and fewer people are interested in building their own helicopters.’

Curriculum vitae

William Thielicke became interested in biomimetics, the imitation of ‘natural designs’ to solve technological problems, while studying biology at Humboldt University in Berlin. He continued the research he conducted for his Master’s thesis (partly at the University of Groningen) with PhD research at the University of Groningen and the Hochschule Bremen, which is where his supervisor, University of Groningen researcher and Professor of Biological Fluid Mechanics & Locomotion, Eize Stamhuis, also works.

More information

-         William Thielicke will be awarded a PhD by the University of Groningen on 31 October for the research done in the research group Ocean Ecosystems of the Energy and Sustainability Research Institute Groningen (ESRIG). The title of his thesis is The flapping flight of birds - Analysis and Application. His promotors are prof.dr. E.J. (Eize) Stamhuis en prof.dr. A.G.J. (Anita) Buma.
-         Contact: William Thielicke