Octopus arms have almost infinite degrees of freedom and perform complex movements such as reaching, grasping, fetching, crawling, and swimming. The abilities come from the intricate organization and biomechanics of the internal muscles.
Researchers in a multidisciplinary project at the University of Illinois Urbana-Champaign tackled the task of understanding how octopi can achieve such a wide range of activities and reported in Proceedings of the Royal Society A. They developed a physiologically accurate model of octopus arm muscles, creating a framework for designing and controlling soft robots. Soft robots perform complex tasks in unstructured environments and work safely around humans.
The octopus has three major internal muscle groups—longitudinal, transverse, and oblique—that cause the arm to deform in several modes—shearing, extending, bending, and twisting, giving the soft muscular arms significant freedom.
The team wanted to express the arm musculature using a stored energy function, a concept borrowed from the theory of continuum mechanics. Interpreting muscles with stored energy simplifies the arm’s control design and solving manipulation tasks such as reaching and grasping. The model led to life-like motion.
The team will look at the biological implications of energy-based control in the future.