Brittle star underwater

Brittle starfish inspires robot design with expendable limbs

Image credit: Dreamstime

The brittle star - an echinoderm closely related to the starfish - has served the inspiration for a new type of robot capable of adapting to physical damage. This could make them resilient the dangers of some environments in which they may be expected to operate.

Researchers at Tohoku University, Japan, have developed a robot capable of immediately adapting to unexpected damage. This sets the new family of robots ahead of conventional robots, which typically take tens of seconds or several minutes to recover from unexpected damage due to the computationally intense process of responding to physical damage.

“Robots are now required to work in harsh environments inaccessible to humans, such as disaster areas, distant planets and deep oceans,” the researchers wrote. “A major obstacle in this regard is that robots cannot cope with physical damage to their bodies.”

The team, based at the Research Institute of Electrical Communication at Tohoku University, turned to the brittle star for inspiration for the new family of more resilient robots.

Brittle stars - which are closely related to starfish - are primitive sea creatures which crawl along the sea floor with five thin, expendable arms. These creatures lack a sophisticated central nervous system, but have the unique ability to manage the loss of their whip-like arms by adapting its motion.

The researchers carried out research on ten adult brittle stars, amputating their arms and observing how they were able to coordinate their remaining arms to continue with motion. Based on what they observed from the creatures, they developed a simple mathematical model to describe the motion, and from this, suggested that a robotic version of the brittle star could consist of arms controlled by a simple decentralised mechanism. Each arm kicks back against the ground when it experiences a reaction force.

Developing a robot based on this simple model, the researchers were able to create a sample robot inspired by the brittle stars, PENTABOT, which is capable of continuing to move a few seconds after having an arm destroyed by coordinating its remaining arms appropriately. Due to the low computational cost of adjusting its motion, PENTABOT can react in real-time to unexpected damage.

The researchers hope that their study could help develop robots capable of working in unpredictable, inhospitable environments such as the rubble after a natural disaster or nuclear meltdown.

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