Design and Experimentation of a Robotic Sea Lion with Wings-Head-Tail Coordinated Drive

Underwater robots with high maneuverability are important equipment for ocean exploration. Although the propulsion unit allows underwater robots to obtain a higher speed, it plays a limited role for improving the turning maneuverability, especially for those medium and large-sized ones. This study draws inspiration from the sea lion's high-performance locomotion of foreflipper propulsion coordinated with the attitude adjustment by flexible head and tail, and proposes a robotic sea lion (RSL) to improve the turning maneuverability and enhance adaptability in narrow and complex underwater environments. The RSL has a pair of flapping wings simulating the configuration and locomotion of sea lion foreflippers, and the multi-joint head and tail that have a single-degree-of-freedom multi-link mechanism and the skin of layered flexible silicone. The head and tail can swing in the coronal plane, allowing the RSL to imitate the rapid turning of the sea lion. Finally, a prototype of the RSL is developed and the coordinated performance of the flapping wings, head and tail is verified through a tank experiment. The experimental results show that the turning radius of the RSL in wings-head-tail coordinated drive is 0.38 times the body length, which is significantly smaller than that in differential mode of the flapping wings.