Gone fishing

A remote-controlled 'fish', whose form and kinematics are modelled on the movement of the manta ray, has been developed by a German pneumatic drive specialist.

The 'Aqua ray' (pictured below) provides a manoeuvrable, remote sensing platform with potential applications in the inspection of undersea pipelines and cables.

An innovative water-hydraulic drive unit, coupled with fluidic muscles, produces smoothly flowing muscular movements. Those are then transformed into the dynamic flapping wings that propel it through the water.

The ray was developed by Festo with help from Berlin-based bionics research company Evologics.

It uses Festo fluidic muscles as actuators. These consist of hollow elastomer tubes with integrated woven aramide fibres.

When the muscle is filled with fluid (air or water), its diameter increases and it contracts longitudinally, giving rise to flowing, elastic movement.

The fluidic muscles constitute the Aqua ray's central propulsion and control unit. The water-driven central vane cell pump generates the propulsion energy like a heart by pumping pressure through valves to three opposing pairs of fluidic muscles. The muscles' contraction force transfers to the wings and tail by artificial tendons.

The Aqua ray is highly manoeuvrable and can be operated either as a hydrostatic glider or with actively flapping wings.

Festo claims the ray's form and mode of propulsion makes it suitable for other applications, such as marine research.

Its smooth contours and lack of rotating parts such as propellers make it particularly suitable for use in environmentally sensitive areas.