Hexplorer: A Biomimetic Amphibious Hexapod Robot for Locomotion in Terrestrial and Aquatic Environments

For locomotion in both terrestrial and aquatic environments, amphibious robots require appendages that can bear loads on land and generate propulsion in water. This paper presents the design and experimental evaluation of Hexplorer, a hexapod robot equipped with six identical leg--fin units that provide a total of twelve actuated degrees of freedom. Each unit combines a vertical prismatic hip with a rotary leg--fin comprising a rigid fan-shaped contact frame and a compliant fin. The mechanical parameters of the leg--fin units are jointly optimized to improve adaptability during terrestrial locomotion. A central pattern generator (CPG)-based gait generation algorithm coordinates the twelve joints and automatically switches between crawling and swimming gaits by changing the gait mapping. In experiments, the robot traveled at 0.0208 m/s on flat indoor ground, 0.0250 m/s on outdoor unstructured ground, 0.1250 m/s at the water surface, and 0.0357 m/s on an underwater substrate. Using the same appendages and actuators, Hexplorer achieves coverage of four locomotion scenarios. JIRS categories: (3) and (6)