Rhythm-Based Power Allocation Strategy of Bionic Tail-Flapping for Propulsion Enhancement

Abstract

With the vast demand in marine development, robotic fish show promising potential in underwater exploration for their high-performance propulsion ability. However, fish-inspired robots are yet to utilize the structural flexibility of rhythmic actuation such as bony fish (Osteichthyes). The Body and Caudal Fin (BCF) locomotion in fish optimizes the use of muscle power and body flexibility by synchronizing muscle activation with the undulating-oscillatory tail-flapping, such as Thunniform, while robotic fish are primarily designed as motion trackers rather than as efficient swimmers. In this paper, we propose a power allocation strategy (PAS) that imitates muscle rhythmic actuation, which increases the flapping amplitude by the coupling of the peduncle motion and the tail deformation. Inspired by this peduncle-tail mechanism, we developed a Direct-Drive Fish Robot (DDRFishBot). The DDRFishBot is enhanced by our developed PAS in Tail-Elastic Potential Energy (T-EPE) release by 228%, in propulsion by 45.6% and in efficiency coefficient by 16.3%. This study establishes the performance enhancement principle of exploiting tail flexibility through a simple scotch yoke mechanism, expanding the performance space of fish-inspired tail-flapping swimming robot.