In this study, the dynamics of the symmetric oscillation and turning characteristics of a flexible fin underwater robot propelled by two fins were studied. First, a three-dimensional model of a robot was established using three-dimensional software. Then, a fluid simulation experiment was conducted and a dynamic model of a flexible fin was established. The deformation of the flexible fin during symmetric undulations was studied. A motion equation for the wave track of the outer edge of the fin surface was also established. This motion equation was simulated and verified. Finally, an experimental prototype was fabricated to verify the simulation results. The results show that if the robot fish oscillates symmetrically using bilateral flexible pectoral fins, it can remain suspended, float vertically, or dive in the water. Its average turning speed can reach 0.8 rad/s, its straight running speed is 0.5 m/s, and its vertical ascending and descending speed is 0.1 m/s. Because a turn made by the robot fish is only driven by its pectoral fins, its turning radius is 0. The results show that the flexible fin underwater robot provides more abundant turning methods, better maneuverability, and higher turning efficiency. This research into the motion of the robot body for different wave parameters when the two fins move together provides a theoretical basis for the cooperative motion of two fins.
