Design and performance evaluation of an amphibious spherical robot

•We describe an amphibious spherical robot, which is capable of motion on land, as well as underwater.•The amphibious robot has two actuation systems: a quadruped walking actuation system and a water-jet actuation system.•The amphibious robot can move with a relatively high velocity and for a relatively long period of time on land and underwater.•The amphibious robot can carry the micro-robot, which is used as a manipulator underwater.

This paper presents an amphibious spherical robot that consists of a sealed upper hemispheroid, two quarter spherical shells, and a plastic circular plate. It has a plastic shelf for carrying the micro-robots, and four actuating units for movement. Each unit is composed of a water-jet propeller and two servomotors, each of which can rotate 90° in the horizontal and vertical directions. The robot is capable of motion on land, as well as underwater. The robot is capable of three walking gaits; therefore, we describe experiments on various terrains to evaluate the walking motion performance, including stability and velocity. Additionally, plenty of underwater experiments are conducted to evaluate the underwater performance, containing horizontal and vertical motions, and to verify the fixture and deployment mechanism for the micro-robot.