Pitch and roll control using independent movable floats for small underwater robots

In this paper, we propose a pitch and roll control system based on a float-shift mechanism for small underwater robots. The proposed system presented here takes advantage of the restoring moment generated by the gravity force and the buoyancy force. The proposed system can maintain the attitude of a robot in its desired orientation. In previous works, we developed a prototype system that only controls the pitch angle of a robot. This paper extends the control system to provide roll and pitch control. In this paper, we explain the static model of the proposed system and how to control the pitch and roll angles of an underwater robot. Next, we conduct numerical analysis in order to investigate the performance of the proposed system. Lastly, we show that the proposed system is able to change the pitch and roll angles of an underwater robot though several experiments in a test tank.