Amphibious piezoelectric travelling wave micro-vehicle based on rigid-flexible composite bionic fins

Amphibious robots increasingly target refined micro-environments, with miniaturization being key to tapping their potential. Inspired by the locomotion mechanism of stingrays and the pectoral fins of carp, two types of fins are proposed respectively: a traveling wave pectoral fin and a caudal fin. Taking the traveling wave pectoral fin as the core driving component and the caudal fin as the auxiliary driving component, an amphibious piezoelectric travelling wave micro-vehicle (APTWM) is constructed. The length, width, and height of the APTWM are 230 × 150 × 79 mm respectively. The traveling wave pectoral fin propels the APTWM to accomplish various movements underwater and on land. The caudal fin drives the APTWM to rotate around its own center of mass. Through their synergistic drive, combined with the pressure-resistant characteristics of the piezoelectric bimorph, the APTWM achieves the capability to reach any water depth. To reveal the locomotion mechanism of the APTWM, numerical simulation is adopted to analyze the propulsion mechanisms of the traveling wave pectoral fin and the caudal fin respectively. Based on this locomotion mechanism, a motion control strategy for the APTWM is proposed. An APTWM prototype has been developed, and relevant experiments have been conducted to test its motion characteristics and motion performance. Tests show that the APTWM can reach a maximum linear motion velocity of 32.05 mm/s (0.13 BL/s) underwater, with a maximum pitch-up angle and pitch-down angle of 30° and 32° respectively. On land, its maximum linear motion velocity can reach 40.24 mm/s (0.17 BL/s). Finally, the dual-mode synergistic drive capability, amphibious switching capability, and load performance of the APTWM were tested. The APTWM demonstrated strong maneuverability and adaptability in the amphibious transition environment. With a 60 g load, APTWM achieved 32.06 mm/s underwater and 9.06 mm/s on land. The APTWM holds broad application prospects in complex amphibious micro-environments.