Flying through the sea of air with collective behaviour 2 Penguins are fascinating creatures which have lost their ability to fly in the course of their phylogenetic development as marine birds. With the AirPenguins, the engineers have created artificial penguins and taught them “autonomous flight in the sea of air”. The knowledge acquired from this research project of Festo’s Bionic Learning Network is to be put to use for future requirements in the automation of production processes. AirPenguin – technology-bearers for adaptive flapping-wing mechanisms The AirPenguin is an autonomously flying object that comes close to its natural archetype in terms of agility and manoeuvrability. It comprises a helium-filled ballonett, which has a capacity of approx. 1 cubic metre and thus generates approx. 1 kg of buoyant force; at each end of the ballonett is a pyramid-shaped flexible structure of four carbon fibre rods, which are connected at joints by a series of rings spaced approx. 10cm apart. The rings together with the carbon fibre rods yield a 3D Fin Ray®structure that can be freely moved in any spatial direction. The Fin Ray®structure was derived from the anatomy of a fish’s fin and extended here for the first time to applications in three-dimensional space. Each pair of spatially opposed carbon fibre rods is connected via bowden wires and a double pulley, and can be extended and retracted in contrary motion by means of an actuator. This gives rise to rotation free of play both at the tip of the AirPenguin’s nose and at the end of its tail. By superimposing two perpendicular planes of rotation, any desired spatial orientation can be realised. A strut to which the two wings are attached passes through the helium-filled ballonett. This new type of wing design can produce either forward or reverse thrust. Each wing is controlled by two actuators: a flapping actuator for the up-and-down movement of the wings, and a further unit that displaces the wing strut to alter the pressure point of the wings. There is also a central rotational actuator for the two flapping wings that directs their thrust upwards or downwards, thus making the AirPenguins rise or descend. All three actuators are proportionally controlled. This makes for continuously variable control of the flapping frequency, forward and reverse motion, and ascent and descent. The entire wing complex comprises a strut with flat flexible wings of extruded polyurethane foam. The wing strut, which is supported at the pivot point of the torso, can be moved either towards the front or rear edge of the wing. Displacing the strut towards the front, for example, causes the wing’s pressure point to migrate forwards. The pressure of the airstream bends the cross-section of the wing in such a way as to produce a profile that generates forward thrust. If the wing strut is moved towards the rear edge of the wing, the pressure point is likewise moved to the rear, and the AirPenguin flies backwards. With this design a self-regulating, wing pressure-controlled, passively twisting adaptive wing has been realised for the first time.
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