The prototype robot octopus arm. HIT PLAY, ABOVE, TO SEE IT WRAP AROUND A HAND UNDERWATER.
Credit: Massimo Brega
The robot octopus arm wraps around two fingers.
Credit: Massimo Brega
ADELAIDE: A robotic octopus arm is being built for deep-sea exploration, but the first prototype testing is throwing up unforeseen challenges for such 'soft-bodied robots', Italian robotocists have said.
The so-called 'soft-bodied robots' have no rigid architecture, so they can stretch, shrink, fit through holes and grasp odd-shaped objects - all while underwater and with no light.
"The octopus represents the highest challenge in the direction of soft-bodied robots," said co-ordinator of Project OCTOPUS, Cecilia Laschi from Scuola Superiore Sant'Anna, Pisa. "Robots with a soft body can be more helpful in all those tasks where they need to enter small apertures, like exploration tasks."
Learning from nature
Researchers with Project OCTOPUS are mimicking the biology of the common octopus (Octopus vulgaris). "The octopus has no rigid structures," said Dr Laschi, "but it can apply very high forces in the environment and accomplish grasping and manipulation tasks."
Humans have a musculo-skeletal body, so our skeleton supports muscle movement. But an octopus has no skeleton. Instead, its muscles provide both movement and support. The same system is found in elephant trunks and the human tongue.
What the researchers are mimicking is a 'muscular hydrostat': muscles are packed in a three-dimensional array, with each fiber stretching either along the arm (longitudinal), across it (transverse), at an oblique angle or the fibre might wrap around other muscles (helical).
Muscles supporting muscles
Because muscles are almost completely incompressible, no matter what the movement is, the arm always keeps the same volume - whether it is long and thin or short and fat.
During movement some muscles contract and force nearby fibres to change shape. These muscles provide support by either opposing or promoting the movement.
Project OCTOPUS substitutes muscle fibres for cables, controlling contractions with soft actuators within in the robot arm. It can sense objects using flexible tactile sensors embedded in the silicone surface.
The researchers finished building the arm prototype in November and have now finished testing it.
"The test aimed at evaluating the performances of the arm generating the basic octopus movements: bending, shortening and elongation," said Matteo Cianchetti from Project OCTOPUS. "The arm is able to accomplish all the tasks, but we noticed the need to improve the efficiency of the motion mechanism.
