Festo develops bionic jellyfish
4 Jun 2008
According to Festo, these small autonomous systems could work together to solve large-scale problems through strategic cooperation. As an artificial autonomous jellyfish with an electric drive unit and an intelligent adaptive mechanism, AquaJelly emulates swarming behaviour in jellyfish.
The AquaJelly's translucent hemispherical dome houses an annular control board with integrated, pressure, tight and radio sensors. The orientation of the propulsion system is constantly monitored by a processor. The control board also contains eight white and eight blue LEDs, which together with the sensors allow communication between several AquaJellies.
Externally, AquaJelly has two concentric silver rings coated with conductive metal paint; connected to these is a charging control unit that supplies the jellyfish with energy. When AquaJelly approaches a charging station located above the water surface, it is drawn towards it and supplied with electricity. The charging station comprises a Festo vacuum generator with integrated contact points for transferral of the energy for charging.
The AquaJelly communicate with the charging station to ensure that each jellyfish is supplied with sufficient energy. The central component of AquaJelly is a watertight laser-sintered body that houses a central electric motor, the two lithium-ion polymer accumulator batteries, the charging control unit and the actuators for the swash plate.
lf a flank is put under tension, the geometrical structure automatically bends in the direction of the applied force. The delayed activation of the eight tentacles via the rhombic joints gives rise to a regular wavelike motion, which generates propulsion. The tentacles together produce a peristaltic forward motion and Festo is exploring applying this principle to automation tasks including a very fast and efficient divert system and a novel gripper finger.
Controlling AquaJelly's motion in 3D space is effected by weight displacement. Two actuators integrated into the central watertight body control a swash plate, which operates a four-armed pendulum. When the pendulum moves in a particular direction, AquaJelly's centre of mass is displaced and the jellyfish then moves in the direction of the displacement.
The sensor system comprises three components that use different media. A pressure sensor makes it possible to determine AquaJelly's depth in the tank to within a few millimetres. AquaJelly is thus aware of its precise position at all times and can position itself within a specific pressure zone. It also relies on the pressure sensor for recharging, since this is the only way it can strategically swim to the surface.
For communication at the water's surface AquaJelly uses the energy-saving ZigBee short-range radio system, which enables it to exchange data with the charging station and to signal to other AquaJellies at the surface that the station is occupied. The radio waves penetrate to a physically determined minimal depth, and AquaJelly must decide within a narrowly defined range which charging station it will approach.
AquaJelly is fitted with eleven infrared LEDs located on a ring inside its dome. These LEDs have a 20 degree aperture angle and use pulsed infrared signals. AquaJelly can communicate within an almost spherical surrounding space to a distance of about 80 cm. When it receives a positional signal from another approaching jellyfish, for example, AquaJelly can thus take evasive action in good time. In addition to the sensors that monitor its surroundings, AquaJelly is also fitted with an internal sensor system that monitors its energy condition and a solenoid switch that enables it to register the orientation of the propulsion system.
