Abstract: We proposed and implemented a leg-vector water-jet actuated spherical robot and an underwater adaptive motion control system so that the proposed robot could perform exploration tasks in complex environments. Our aim was to improve the kinematic performance of spherical robots. We developed mechanical and dynamic models so that we could analyze the motions of the robot on land and in water. The robot was equipped with an Inertial Measurement Unit (IMU) that provided inclination and motion information. We designed three types of walking gait for the robot, with different stabilities and speeds. Furthermore, we proposed an online adjustment mechanism to adjust the gaits so that the robot could climb up slopes in a stable manner. As the system function changed continuously as the robot moved underwater, we implemented an online motion recognition system with a forgetting factor least squares algorithm. We proposed a generalized prediction control algorithm to achieve robust underwater motion control. To ensure real-time performance and reduce power consumption, the robot motion control system was implemented on a Zynq-7000 System-on-Chip (SoC). Our experimental results show that the robot’s motion remains stable at different speeds in a variety of amphibious environments, which meets the requirements for applications in a range of terrains.

Key words: Bionic amphibious spherical robot , · Inertial measurement unit , · Quadruped gaits , · Forgetting factor least squares algorithm , · Generalized prediction control