Development of a Turtle-inspired Robot with Variable Stiffness Hydrofoils

Motivated by the body structure and movement of sea turtles, this paper proposes a novel mechanical design of an innovative turtle-inspired robot system for both efficient fast swimming and high spatial maneuverability. The robotic sea turtle is driven by two variable stiffness fore hydrofoils to produce thrust and two soft hind hydrofoils to control the movement direction. Considering the long-time observation in a wide ocean, the centre of gravity adjustment mechanism and the buoyancy adjustment mechanism are developed to keep the robot glide in a lower pow manner. The modular layout of the overall structure also brings greater potential for its robustness. With ANSYS-based simulation, we analysed the propulsion efficiency of variable stiffness hydrofoils with different stiffness and different flapping frequencies through computational fluid dynamics technology (CFD), to conduct intuitive and non-disturbing monitoring of fluid phenomena during motion, revealing the principle of variable stiffness hydrofoils in optimizing propulsion capability in fluid fields.