Kinetic analysis and design of a bio-inspired amphibious robot with two undulatory fins

This paper presents a novel amphibious robot inspired by Gymnarchus niloticus. The robot prototype is comprised of undulatory fins, shell and robot body. The undulatory fins are symmetrically placed on each side of the robot, which enable the robot to swim underwater as well as crawl on the ground. The undulatory fin consists of membrane and rigid fin rays which are actuated by brushless motors. To provide some guideline on the design of the fin and motors, the generation mechanism of thrust driving the robot to move from aquatic to terrestrial environment is investigated by the means of numerical computation method. Through kinetic analysis, we find that the fin should keep a balance between flexibility and rigidity. Here a mechanical way to fabricate the fin by exerting force to the original flexible membrane is proposed. With two such fins integrated into the robot, the robot can achieve three-dimensional motion underwater as well as crawl on the ground. Experiments show that the robot featuring with undulating motion and flapping motion has remarkable maneuverability.