Passive and active attitude stabilization method for the spherical underwater robot (SUR-II)

This paper introduces the passive and active attitude stabilization control for a spherical underwater robot (SUR-II). Due to the special structure of the robot, we involve passive attitude stabilization method both in pitch and roll directions. We adjust the distance between the center of buoyancy and the center of gravity to generate restoring moment. The restoring moment is used to realize passive attitude stabilization in pitch and roll directions. But for the yaw direction, because the robot is centrosymmetric and the water resistance is small and there is no restoring moment, active attitude stabilization control is necessary. For the active attitude stabilization, we employ Rotation Vector algorithm to instead Euler angle algorithm. The Euler angle algorithm decomposed the rotation motion into 3 orderly rotational motions in pitch, roll, yaw direction respectively. But the Rotation Vector algorithm can describe the rotation motion of the spherical underwater robot just in one time. It is very convenient to control the rotational motion. Finally, we carry out a stabilization experiment to verify the active attitude stability in yaw direction. The experimental results show that the robot can realize attitude stabilizaiton in a short time.