Design and Implementation of a Soft Robotic Fish Based on Carangiform Fish Swimming

In the past decade, numerous underwater robots have been proposed. Nevertheless, the complexity of their designs diminishes their applicability in real-life scavenging missions. This paper proposes an optimized design of a fish-wise robot, mimicking the undulatory motion of a Carangiform fish alongside delicate performance in suboptimal tail-beat frequencies. This source of inspiration allows the robot to have high efficiency besides weight considerations. A novel traction system is embedded in the newly designed power transmission unit to exert a sinusoidal pattern of push and traction of the wires. The structure is made up of a cable-driven body connected to a compliant structure via CT sheet to eliminate joint friction and also enhance the robustness of the robot. The prototype body geometry was carefully examined through kinematic modeling. Later on, a prototype has been built and underwent experiments to verify the final results. The robot was able to accomplish an acceptable and trustable lateral motion at lower and higher designed frequencies. At the 2-hertz frequency of tail-beat, the ideal frequency, the lateral motion had a maximum error of 7%. The results were satisfactory, accomplishing the desires.