A Novel Underwater Robot with Carangiform Locomotion Achieved via Single Degree of Actuation and Magnetically Transmitted Traveling Wave

The phenomenon of the “traveling wave,” commonly observed in various organisms, involves a wave that propagates along the body, serving as a locomotion mechanism. Particularly, in aquatic environments, organisms such as fish and cetaceans utilize traveling waves to propel themselves through water, minimizing fluid drag and maximizing movement efficiency. Inspired by nature, robotics has extensively explored replicating such locomotion strategies. This work presents a fish robot with an innovative magnetic transmission system. The mechanism transforms the unidirectional rotation of a single motor into an oscillatory, phase-shifted movement across the modules of the kinematic chain, generating a traveling wave along the body. The robot's design and functionality are detailed, highlighting advancements in bio-inspired robotics for underwater applications, such as efficient and non-invasive monitoring and exploration of marine ecosystems. The fish robot achieved a swimming speed of approximately 2 body lengths per second (BL/s) with a tail-beat frequency of 3.24 Hz and a minimum Cost of Transport (CoT) of $5.33 ~\mathrm{J} /(\text{kg} \cdot \mathrm{m})$. Biomimetic robotics can play a key role in sustainable aquafarming, biodiversity conservation, and animal-robot interaction research, offering the potential to minimize ecosystem disruption and advance marine science.