Inspiration for innovation often comes from the impressive talents of Mother Nature. Researchers at the University of Southern California (USC) Viterbi School of Engineering believe that is especially the case when it comes to the seemingly motionless yet uniquely moving sea star. Understanding these sea creatures’ unique sensory-driven motion has the potential to enhance the complex motions of future robotics.
How a sea star moves has long been a wonder for scientists. These creatures have hundreds of tubes on their undersides that allow them to move and hold on to prey or terrain. These tubes can autonomously respond to stimuli, creating a relatively fast bouncing motion. However, since sea stars have no brain and have a decentralized nervous system, how they coordinate that movement has remained a bit of a mystery.
In their study, the USC researchers determined that a sea star’s dominant arm provides a global directional instruction that the other arms then follow.
“The nervous system does not process everything in the same place at the same time but relies on the idea that the sea star is competent and will figure it out,” said Professor Eva Kanso, a Zohrab A. Kaprielian Fellow in Engineering. “If one tube foot pushes against the ground, the others will feel the force. This mechanical coupling is the only way in which one tube foot shares information with another.”
Building on established work, the team’s research delved deeper into the creature’s actual motion, especially its synchronized bouncing. During regular crawling, a sea star’s arms move in the same direction but are not synchronized. That changes when it speeds up for bouncing—sometimes tens of feet. These movements don’t align with prevailing modes of locomotion for most other creatures, which are sensory feedback or individual responses.“In the case of the sea star, the nervous system seems to rely on the physics of the interaction between the body and the environment to control locomotion,” Kanso said. “All of the tube feet are attached structurally to the sea star and, thus, to each other.”
The team developed a new locomotion model that includes an information mechanism that communicates between the tube feet. Since the feet are connected, one tube’s response triggers another tube’s response. As the sea star moves, the force of each individual movement eventually becomes synchronized.
Better understanding the complex coordination of a sea star has the potential to be a steppingstone for future robotics. Although artificial intelligence (AI) and other innovations are creating smarter robots, there are still limitations when it comes to complex movements. For example, a robot can be programmed for a repetitive pick and place task, but what if it could intuitively “communicate” with other robots or synchronize tasks based on situational changes?
“Using the example of a sea star, we can design controllers so that learning can happen hierarchically,” Kanso said. “There is a decentralized component for both decision-making and for communicating to a global authority. This could be useful for designing control algorithms for systems with multiple actuators, where we are delegating a lot of the control to the physics of the system—mechanical coupling—versus the input or intervention of a central controller.”
Interested in more nature-inspired innovations? Check out Flying Fish Robot Has Unique “Engine” and Robots Learn Swarm Behaviors, Aim to Escape the Lab.