Imagine a sophisticated network of interconnected autonomous robots. They operate in unison, like an elaborate water ballet, navigating the pitch-dark depths of the ocean, conducting detailed scientific surveys and high-stakes search-and-rescue missions. This futuristic vision is getting closer to reality, thanks to researchers at Brown University, who pioneered the development of a new type of underwater navigation robot. One such robotic platform, called Pleobot, was the star of their recently published study Scientific Reports.
Krill, a small crustacean that serves as an important part of the marine ecosystem, are exceptional swimmers with extraordinary abilities in maneuverability, acceleration and turning. Their extraordinary athletic abilities have inspired researchers at Brown University to develop the Pleobot—a robotic platform consisting of three articulated parts that mimics the swimming style characteristics of metachronal krill.
“The pleobot allowed us unparalleled resolution and control to investigate all aspects of krill-like swimming which helped it excel in underwater maneuvers,” said Sara Oliveira Santos, Ph.D. candidate in Brown’s School of Engineering and lead author of the study.
The research team aims to use Pleobot as a comprehensive tool to understand krill-like swimming and harness its 100 million year evolutionary potential to engineer better robots for ocean navigation.
Pleobot Mechanism: Mimicking the Swimming Magic of Krill
The Pleobot Project is an international collaboration between Brown University and Universidad Nacional Autónoma de México. Together, they solve the mystery of how krill, known as metachronal swimmers, navigate complex marine environments and make colossal vertical migrations of more than 1,000 meters twice a day—the equivalent of stacking three Empire State Buildings together.
“We have a picture of the mechanisms they use to swim efficiently, but we don’t have comprehensive data,” explains Nils Tack, postdoctoral fellow in the Wilhelmus lab at Brown University.
The team has built and programmed Pleobot to precisely mimic krill leg movements and change the shape of appendages, providing new, deeper understanding of fluid-structure interactions at the appendage level.
Pioneering the Future of Autonomous Underwater Vehicles
According to the researchers, the metachronal swimming technique allows krill to maneuver very well, displaying a sequential deployment of their swimming legs in a wave-like motion. This characteristic is something they believe can be incorporated into a herd system that can be implemented in the future. Monica Martinez Wilhelmus, Assistant Professor of Engineering at Brown University, asserts, “Being able to understand fluid structure interactions at the complement level will allow us to make informed decisions about future designs.
These future swarms of robots could map Earth’s oceans, participate in extensive search and recovery missions, or even explore the oceans of moons in our solar system, such as Europa. Wilhelmus added, “Krill aggregation is an excellent example of swarming in nature… This study is the starting point of our long-term research goal to develop the next generation of autonomous underwater sensing vehicles.”
The Significance of Pleobot Design
Pleobot construction involves a multidisciplinary team specializing in fluid mechanics, biology and mechatronics. Its components consist primarily of 3D printable parts, and the design is open-source. Researchers have replicated the opening and closing motion of a biramous krill’s fin, which is believed to be a first for such a platform. The model is built at ten times the krill scale, which is typically the size of a paper clip, allowing for more accurate observation and analysis.
“In published studies, we reveal the answer to one of the many unknown mechanisms of krill swimming: how they generate lift to avoid sinking while swimming forward,” said Oliveira Santos. “We can unravel the mechanism using robots,” added Yunxing Su, a postdoctoral fellow in the lab. They found that an area of low pressure on the back of the swimming leg contributes to increased lift during power strokes of the moving leg, a finding important for understanding and replicating krill efficient swimming.
The Brown University team’s pioneering work with Pleobot marks a significant leap forward in efforts to develop the next generation of autonomous underwater sensing vehicles. The possibilities seem as wide as the ocean this robot wants to explore.