Screw propellers, while commonly used in underwater propulsion, suffer from issues such as entanglement, noise, and reduced visibility. In contrast, fish tail fin propulsion offers minimal environmental impact, superior obstacle avoidance, and high maneuverability in confined spaces, thus exhibiting excellent compatibility with underwater environments. Consequently, fish-like robots are considered promising for underwater exploration in disaster zones and ecological surveys. Although various fish-like robots have been developed, replicating the smooth, continuous streamlined shape of real fish using multi-link structures remains challenging. While flexible materials have been employed to create continuous structures, issues concerning body shape and surface integrity during swimming persist. Therefore, this study aims to develop a robot that maintains a continuous streamlined body shape using a silicone-based outer skin. The robot’s external shape is designed based on 3D scan data of Japanese horse mackerel, and a wire-driven bending mechanism with a flexible outer skin that prevents wrinkling during bending is developed. Swimming experiments demonstrated that the developed robot maintained a smooth and continuous body structure without wrinkles during bending, successfully replicating carangiform swimming, particularly the coordinated movement of the tail fin and body. Furthermore, the relationship between the robot’s swimming speed and tail fin frequency closely matched that of a real horse mackerel, confirming the achievement of efficient swimming.
NAKANISHI et al. (Sun,) studied this question.