The manta-inspired robot swims up and down at speeds of up to 6.8 body lengths per second. Jie Yin and Haitao Qing, NC State University
Researchers have set a new record for the fastest swimming soft robot, inspired by manta rays for improved movement control.
A team at North Carolina State University (NC State) has improved its previous design of an aquatic soft robot, increasing its speed from 3.74 to 6.8 body lengths per second.
The new design is more energy-efficient and capable of swimming throughout the water column, whereas the previous model was limited to surface swimming.
“Studying the fluid dynamics of manta rays also played a key role in controlling the vertical movement of the soft robot,” said researchers in a statement.
Soft robot swims
The soft robot features fins inspired by those of a manta ray and is made from a material that remains stable when the fins are spread wide.
Attached to a flexible silicone body, the fins are connected to an air-filled chamber. Inflating the chamber bends the fins, mimicking the downward stroke of a manta ray’s fin flap.
When the air is released, the fins snap back to their initial position. According to researchers, the mechanism enables energy storage in the system, with the fins returning to their stable state after air is released, allowing for rapid actuation with only one actuator.
The fluid dynamics of manta rays influence the design’s ability to control vertical movement. By studying their swimming motion, researchers replicated this behavior to enable the robot to swim upwards, downwards, or maintain its position in the water column.
Manta rays produce two jets of water to propel themselves forward and alter their trajectory by changing their swimming motion. A similar technique is used in the robot to control its vertical movements, enhancing its ability to navigate the water.
The team is continuing to refine methods for fine-tuning the robot’s lateral movements, aiming to improve its overall control and versatility in aquatic environments.
Robot masters buoyancy
Simulations and experiments revealed that the soft robot’s downward jet is more powerful than its upward jet. When the robot flaps its fins quickly, it rises, but slowing the actuation frequency allows it to sink slightly between flaps, enabling it to dive or maintain its depth.
The use of compressed air in the robot also affects its buoyancy. When the fins are at rest, the air chamber is empty, reducing buoyancy. However, when the robot flaps its fins quickly, the chamber fills more frequently, increasing buoyancy.
The robot’s capabilities were demonstrated in two ways: one iteration navigated a course of obstacles on the surface and floor of a water tank, while another untethered version was able to haul a payload, including its own air and power source, on the surface.
Despite its complex design, the underlying principles are simple. With just a single actuation input, the robot can navigate a vertical environment effectively.
According to the team, it demonstrates the versatility and functionality of the soft robot, which has been designed to handle various underwater challenges and tasks with minimal energy consumption and a straightforward control system.
“We are now working on improving lateral movement and exploring other modes of actuation, which will significantly enhance this system’s capabilities. Our goal is to do this with a design that retains that elegant simplicity,” said Jie Yin, an associate professor of mechanical and aerospace engineering at NC State and corresponding author of the research paper, in a statement.
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The details of the team’s research were published in the journal Science Advances.
