Theoretical Modeling and Performance Analysis of a Wave-Powered Multi-Joint Submersible Robot

The limited endurance of autonomous underwater vehicles has motivated the development of in situ wave energy harvesting. This paper proposes a novel wave-powered multi-joint submersible robot that integrates articulated joints with buoyancy bladders, pectoral fins, suction attachment, and retractable propellers. A cable-driven transmission and clutch-enabled power take-off (PTO) system allows the robot to harvest wave energy via relative pitch motions and switch to active propulsion. A coupled hydrodynamic model is established based on linear potential flow theory in both frequency and time domains. Numerical simulations investigate the effects of wave period, amplitude, PTO damping, and irregular sea states on dynamic responses and energy capture. Results reveal that relative pitch motion at the central joint dominates energy capture, contributing approximately 73% of total harvested energy. The system exhibits multi-resonant peaks from 1.1s to 2.2 s, enabling broadband adaptability. Under irregular waves, the captured power reaches approximately 5 W at Hs = 0.2 m. The proposed design demonstrates promising energy harvesting performance, offering a viable solution for extending the endurance of ocean robots.