Cooperative Motion Mechanism of a Bionic Sailfish Robot With High Motion Performance

The sailfish possesses outstanding motion performance among marine species, while the robotic fish using the sailfish as a bionic object has received little attention. In this letter, the shape structure and motion characteristics of sailfish are observed, and a bionic sailfish robot is designed that can perform cooperative motion through the dorsal and caudal fins. A novel bionic motion rhythm is developed based on the tail motion characteristics of sailfish, and its propulsive performance is evaluated using experimentation and simulation. The mechanism of cooperative motion between the dorsal and caudal fins is explored from the vortex's perspective, and it is concluded that the vortex formed by the dorsal fin can enhance the propulsive performance of the caudal fin. The results reveal that the phase difference between the dorsal and caudal fins during cooperative motion has a significant effect on the forward speed of the bionic sailfish robot. The average speed of the robotic fish is up to 1.24 m/s when the phase difference is 180°. The turning radius is minimized when the dorsal and caudal fins cooperate in the motion, and a highly maneuverable motion mode is achieved. A high motion performance has been shown by the robotic fish from the perspectives of motion speed, turning performance, and high maneuverability motion mode.