Reading University researchers are taking part in a multi-disciplinary effort to develop a robotic octopus. The biomimetic cephalopod is being designed to match a real octopus in terms of speed, dexterity and flexibility. Possible uses for the autonomous, battery-powered device include underwater maintenance, marine salvage and retrieval of objects, such as black-box recorders from crashed aircraft.
In nature, an octopus contains no rigid structures and is capable of adapting the shape of its body to the environment it is in, including very confined spaces. This lack of rigid structure means that the octopus has an infinite number of degrees of freedom; it can twist, elongate and bend its arms in all directions. Despite the lack of skeletal support, the octopus can vary the stiffness in its arms to apply force.
Dr Richard Bonser from Reading University’s School of Construction Management and Engineering has been awarded £649,000 as part of an EU consortium to design eight arms that mimic the dexterity and control of the marine invertebrate. This includes the suckers on the arms and waterproof skin. Bonser told The Engineer that the arms will mimic the octopus’ muscular hydrostat (muscular structures with no skeletal systems), negating the requirement for joints. ‘Essentially they won’t have any joints because the construction of the robot is given over to the entirely soft body,’ said Bonser. ‘At the moment there is one set of actuators at the base of each arm, because it appears from octopus behaviour that the octopus can achieve quite complex patterns of movement simply by rotating the base of each arm.’ Mimicking the muscular hydrostat will give the arms a constant volume too, so all the arms will perform fluidly. Bonser added that this fluid movement would likely reduce the amount of friction between the underlying actuator, which is being designed at Reading too.
In use, the robot octopus will have to be able to grip onto objects and structures, presenting challenges for the design of the actuation and control mechanism of suckers on each arm. ‘Purely by chance, we came across another sucker system that appears to operate entirely passively,’ said Bonser. ‘I’d bought a squid at a fishmongers and was preparing it in my sink at home when I found, despite it being very dead, having been frozen and de-frosted, that its suckers still stuck to the side of the sink. ‘We thought about how it worked and we managed to produce a prototype system that works in the same way.’
Consequently, Bonser and his team were able to manufacture rows of suckers placed along the entire length of the arm that don’t require active actuation to stick to objects. ‘These structures can be 7–8mm in diameter, with a slight concave surface, and each of these can generate a lifting force of around four Newtons,’ he said. To stop water ingress, the Reading team is developing a highly condensable complex material that Bonser said is a combination of a textile and silicon rubber that will maintain a high degree of waterproofing.
So far, the Reading team has one arm that can move around, but it will be a couple more years before all eight move together, said Bonser. ‘We’re half-way through our project, which is four years in duration,’ he said. ‘So we’ve another two years to crack the control and integration of the various mechanical systems.’ The research, ‘Novel design principles and technologies for a new generation of high-dexterity soft- bodied robots inspired by the morphology and behaviour of the octopus’, is led by Scuola Superiore Sant’Anna, Pisa.
Institutions from Greece, Switzerland, Italy and Israel are also involved in the four-year project, which has received €7.6m (£6.6m) in funding from the European Commission.