Exploiting Frictional Effects to Reproduce Octopus-Like Reaching Movements with a Cable-Driven Spiral Robot

Octopus arms possess a remarkable capacity for intricate and diverse motions achieved through sequential deformation of the body. This paper aims to reproduce octopus-like reaching movements (extending the arm towards a target) on a cable-driven spiral robot. Our method capitalizes on the frictional interplay between cables and the robot's structure to enable reaching in various directions with only two cables. We propose an analytical friction model capable of calculating tension distribution along the robot's body, where the trajectory of the actuation is encoded in the direction of friction at each contact point between the cables and the robot structures. Through simulation and real-robot experiments, we establish that frictional effects can be harnessed to expand the cable-driven robot's workspace and mobility and accurately replicate octopus-like reaching movements in various scenarios (Supplementary video: https://youtu.be/RdKK7aeOWzA).