A team of researchers at North Carolina State University (NC State) has set a new speed record for an aquatic soft robot, doubling its speed from 3.74 to 6.8 body lengths per second. This breakthrough, inspired by the efficient movement of manta rays, also enhances the robot’s energy efficiency and expands its ability to swim throughout the entire water column—an improvement over the previous model, which was limited to surface swimming.
The soft robot features fins designed based on the unique fluid dynamics of manta rays. These fins are made from a material that remains stable when spread wide, and they are attached to a flexible silicone body. The design includes an air-filled chamber connected to the fins, which bend when inflated, mimicking the downward stroke of a manta ray’s fin flap. Once the air is released, the fins snap back to their original position, storing energy and enabling rapid actuation with just one actuator.
The study of manta ray fluid dynamics has played a key role in improving the robot’s vertical movement control. The robot can now swim up, down, or maintain its position in the water column by mimicking the manta ray’s water jet propulsion method. By producing two jets of water, manta rays propel themselves forward while altering their swimming trajectory. This technique has been adapted into the robot’s design, allowing for more precise navigation and vertical movement in water.
The robot’s buoyancy is controlled using compressed air, affecting its rise and fall in the water. When the fins are at rest, the air chamber empties, reducing buoyancy, but quick fin flapping fills the chamber, increasing buoyancy and enabling the robot to rise. By adjusting the frequency of the fins’ actuation, the robot can dive or maintain its depth in the water.
The team’s simulations and experiments revealed that the robot’s downward jet is more powerful than its upward jet, which gives the robot greater control over its vertical movements. When the robot flaps its fins rapidly, it rises, and slowing the actuation frequency allows it to sink slightly or maintain its depth.
The robot’s performance has been demonstrated in two ways: one version successfully navigated a course of obstacles on both the surface and floor of a water tank, while another untethered version demonstrated its ability to carry a payload, including its own air and power source, on the surface. Despite its complex design, the robot’s simple actuation input allows it to effectively navigate the vertical water environment.
The researchers are working on refining the robot’s lateral movements and exploring new modes of actuation. These advancements will improve the robot’s control and versatility, expanding its ability to tackle more underwater challenges with minimal energy consumption.
Jie Yin, an associate professor of mechanical and aerospace engineering at NC State and lead author of the research, explained: “Our goal is to enhance the system’s capabilities while keeping the design simple and efficient. We are now focusing on lateral movement and testing other actuation methods to further improve the robot’s performance.”
This new, fast-swimming soft robot, with its sophisticated buoyancy and movement control, represents a significant leap in aquatic robotics, potentially offering new solutions for underwater exploration, environmental monitoring, and other marine applications.
By Impact Lab
