Title: Sea star locomotion
Abstract: The oral surface of sea stars (starfish) is lined with arrays of tube feet that enable them to achieve highly controlled locomotion on various terrains and to even gallop and bounce. The activity of the tube feet is orchestrated by a nerve net that is distributed throughout the body; there is no central brain. How such a decentralized nervous system produces a coordinated locomotion is yet to be understood. To examine the sensorimotor control underlying the sea star locomotory behavior, we developed mathematical models of the biomechanics and sensorimotor control of the tube feet. In these models, the feet are soft actuators that are coupled mechanically through their structural connection to the sea star body, and whose power and recovery strokes are dictated by local sensori-feedback control loops. We found that these minimally-coupled tube feet coordinate to generate robust forward locomotion, reminiscent of the crawling motion of sea stars. We also found that the sea star model can transition from crawling to bouncing, and it can robustly locomote on various terrains, and under various heterogeneity in the tube feet parameters and initial conditions, akin to experimental observations. These findings improve our understanding of the Echinoderms decentralized nervous system and could lead to novel designs and control rules for autonomous robotic systems.
Prof. Eva Kanso is a Professor and the Z.H. Kaprielian Fellow in Aerospace and Mechanical Engineering at the University of Southern California.