Hovering underwater robotic platform with four tilting thrusters

This paper represents a new underwater robotic platform with four tilting thrusters for hovering motion. The tilting mechanism can implement the six degrees-of-freedom (DOF) motion with only four thrusters but causes an increase in the nonlinearity of thrust force vector map. In order to overcome the nonlinearity, the selective switching controller is designed, and applied it to the robot system. The selective switching controller chooses each three-DOF sub-controller according to the error in real-time. The experiment, which a robot maintains the position and orientation under a disturbance from an attached manipulator, is performed in a water tank. The results verify the hovering ability of the robot.