Development of a Bio-robotic Swimmer Based on the California Sea Lion

The development of unmanned underwater vehicles (UUVs) capable of operating in complex environments—such as coastal regions with obstacles and dynamic flows—requires new and effective maneuvering techniques with high agility to overcome the limitations of current underwater systems. UUVs that can operate in these zones have broad applications, including environmental monitoring, defense, and infrastructure inspection. By studying the swimming and maneuvering strategies of marine organisms, researchers can develop UUVs that integrate biologically inspired characteristics to enhance performance. The California sea lion ( Zalophus californianus ) was selected as a biological model due to its swimming and maneuvering capabilities in both the open ocean and through the high-energy surf zone. This paper presents the development of a novel, multi-bodied, bio-robotic system with flipper-based propulsion modeled after the California sea lion. An articulatable head and pelvis, flexible fore flippers that generate 3D forces, and adjustable hind flippers were identified as potential contributors to its mobility, as supported by existing research and video analysis. The system serves as a research platform for systematically evaluating how these features influence swimming and maneuvering. Experimental results demonstrate the system's ability to use hydrostatic and hydrodynamic forces to move repeatably in 3D space, providing a foundation for assessing the role of body articulation and flipper movements in underwater locomotion.