This paper presents a free-swimming, tetherless, cable-driven modular soft robotic fish. The body comprises a series of 3D-printed wave spring structures that create a flexible biologically inspired shape that is capable of an anguilliform swimming gait. A three-module soft robotic fish was designed, fabricated, and evaluated. The motion of the robot was characterized and different combinations of actuation amplitude, frequency, and phase shift were determined experimentally to determine the optimal parameters that maximized speed and minimized the cost of transport (COT). The maximum speed recorded was 0.20 BL/s (body lengths per second) with a COT of 15.82. These results were compared against other robotic and biological fish. We operated the robot, untethered, in a variety of environments to test how it was able to function outside of laboratory settings.

This paper introduces DRAGON: Deformable Robot for Agile Guided Observation and Navigation, a free-swimming deformable impeller-powered vectored underwater vehicle (VUV). A 3D-printed wave spring structure directs the water drawn through the center of the robot by an impeller, enabling it to move smoothly in different directions. The robot is designed to have a narrow cylindrical profile to lower drag and improve agility. It has a maximum recorded speed of 2.1 BL/s (body lengths per second) and a minimum cost of transport (COT) of 2.9. The robot has two degrees of freedom (DoFs) and is capable of performing a variety of maneuvers including a full circle with a radius of 0.23 m (1.4 BL) and a figure eight, which it completed in 4.98 s (72.3 °/s) and 10.74 s respectively. We operated the robot, untethered, in various environments to test the robustness of the design and analyze its motion and performance.