Biomimetic Robotic Remora With Hitchhiking Ability: Design, Control and Experiment

Remora, which is well known for it's ’hitchhiking’ behavior, can attach to diverse marine animals and travel with them for a long distance with low energy consumption due to its special disc. In this letter, inspired by the unique ’hitchhiking’ behavior, a new prototype of a robotic remora with good maneuverability, reliable adhesion system and robust motion control strategy is designed to apply the ’hitchhiking’ behavior to engineered system. In the design of the mechanics, a robotic remora with wire-driven propulsion mechanism and pectoral fins diving mechanism is developed to realize the decoupled planar and vertical motion. Besides, a stable adhesion system with considerable adhesive force( $\sim$ 274 N), low pre-load demand and perception ability is developed. In the aspect of motion control, considering the underactuated characteristics, highly nonlinear and model uncertainty of the robotic remora dynamics, a planar controller consisted of a line-of-sight guidance law and an active disturbance rejection heading controller, and a proportional-integral-derivative based depth controller are adopted. The combination of the two controllers enable the robotic fish to achieve autonomous motion in three-dimensional space, providing strong support for achieving the ’hitchhiking’ behavior. Extensive experiments, including the coordination between the robotic remora and underwater vehicle, have been conducted to verify the reliability of the designed robotic remora and the corresponding control strategy.