Taking a close look at wings in nature

Flying in the Bionic Learning Network

The dream of being able to fly is one of the oldest human dreams. We have always been fascinated by the animal world, which shows in all sorts of ways how flying is done. In the Bionic Learning Network, too, flying is a recurring theme. For years, Festo, in association with universities, institutes and development companies, has been developing research platforms whose basic technical principles are based on nature.

First of all, our bionics experts took a close look at the fins of the manta ray. Although this creature lives in water, its large pectoral fins beat up and down like wings when it swims. We transferred this principle to the Air_ray in 2007. The flow-optimised design of the artificial ray increases aerodynamic efficiency, while the active torsion of the wings ensures that their full force is used. A servo motor pulls alternately on the two flanks in a lengthwise direction and thus moves the wings up and down. With an additional servo drive, the beating wing can be rotated around its transverse axis, so that the Air_ray can also be manoeuvred backwards. Thanks to its lightweight design, the uplift provided by helium and its beating wing drive with Fin Ray Effect®, it moves through the air just its natural role model moves through the water.

A similar concept is also behind the AirPenguins developed in 2009. Their flying technology is very close to the swimming technique of their biological models. The passively twisting wings allow both forward and reverse thrust to be generated.

The AirPenguins are the third group to fly autonomously and float within a defined airspace, which is detected by ultrasound transmitting stations. The penguins can move freely within this space.

A microcontroller gives it the opportunity to explore this space autonomously or according to specific rules.

From water to air

Building on this, in 2011 we deciphered the secret of bird flight and presented the SmartBird. This bionic technology platform, inspired by the herring gull, can start, fly and land by itself – without additional drive.

Not only do its wings beat up and down, but they also twist in a specific manner. This is done by an active articulated torsion drive, which, in conjunction with a complex control system, achieves previously unattained efficiency levels in flight. Continuous diagnostics ensures a safe flight. While the SmartBird is flying, data such as the wing position, the wing torsion or the status of the battery are recorded and checked in real time by the software.

Flying skills of the dragonfly

The kind of flying displayed by the dragonfly is even more complex. Its flying skills are unique: it can move in all spatial directions, remain still in the air and glide without beating its wings at all. Thanks to its ability to move both pairs of wings independently of each other, it can brake and turn abruptly, accelerate rapidly and even fly backwards.

With the BionicOpter our bionics team technically transferred these highly complex properties to an ultra-lightweight flying object in 2013. For the first time, a model can master more flight conditions than a helicopter, a motorized aircraft and a glider combined. By controlling the flapping frequency and rotation of each wing, all four wings can be individually adjusted in terms of the direction and strength of thrust. The remotely controlled dragonfly can thus take up almost any position in space.

Flying as a group

Festo perfected lightweight construction and miniaturization in 2015 with the eMotionButterflies.Each of the bionic butterflies weighs just 32 g. To replicate the flight of their natural role model as closely as possible, the eMotionButterflies are equipped with highly integrated on-board electronics. They can control the wings precisely and individually and thus realize fast movements.

Ten cameras installed in the space detect the butterflies using their infrared markers. The cameras transmit the position data to a central master computer which coordinates the butterflies.

Semi-autonomous flying in a defined space

The bionic engineers have developed this intelligent networking system further and will demonstrate the BionicFlyingFoxat the Hannover Messe 2018. It can fly semi-autonomously thanks to the combination of on-board electronics and an external camera system. This allows the artificial bat, which has a wingspan of 2.28 m, to fly through the air.

An elastic airtight membrane stretches from the tips of the fingers to the feet of the artificial bat. The specially developed membrane consists of a knitted elastane fabric and films welded together at selected points. Thanks to this honeycomb structure, the BionicFlyingFox can fly even if the bionic fabric sustains minor damage.

However different the flying behaviour of animals in the natural world may be, when transferring it to technology, the major challenges are always the lightweight design and functional integration. With the BionicFlyingFox, whose articulation points of the heavily loaded kinematic system are all on one plane so that the wings can be folded like scissors, Festo has now deciphered all the different types of flying found in the animal world. But nature provides many other unique solutions which will inspire the bionics team to find new technical solutions in the future.