Abstract: Inspired by amoebae and snake in the nature, the transformable capability and link-type structure is brought in an amphibious robot. The link-type transformable configuration without adding extra underwater propulsion mechanism is designed for an amphibious robot through analysis on the movement characteristics, extending on the water environment adaptability and transformable ability, which has crawler-swimming propulsion mode and the bionic propulsion mode. The model of the crawler-swimming propulsion mode is established based on the ideal propeller. Aiming at the coupling relationship between the kinematics and fluid force in the fish-like propulsion mode, the associated model on the kinematics and dynamics is put forward based on the Lagrange equation. Together with the steering model, the motion performance of the bionic propulsion is analyzed. The simulation demonstrates the influence of the mechanism parameters such as height and distribution of the track grouser and motion parameters such as amplitude and frequency on the underwater propulsion. The experiments in the water environment performed on the robot prototype Amoeba-II verify the effectiveness of the amphibious link-type transformable configuration, and compare the propulsion efficiency and stability between crawler-swimming propulsion mode and the bionic propulsion mode.

Key words: bionic propulsion, crawler-swimming, link-type transformable configuration, amphibious robot