Mechanical Design and Control of an Underwater Robot for Pitch and Roll Stability

The use of the underwater robot for ship hull cleaning is increasingly studied given the valuable operational, economic and environmental advantages that it offers. The Automatic Control and Marine Robotics Unit, within the Tunisian Naval Academy, has suggested a new underwater robot design that is equipped with two manipulating arms. The offered solution allows to combine a system portability with the improved cleaning efficiency offered by the manipulator arms. However, during underwater operation, the robot, located beneath the ship's hull, is exposed to several perturbation forces. These forces are mainly caused by water current and waves. This research focuses on the robot static and dynamic stability when it is exposed to external perturbations. The proposed approach to ensure the robot stability consists in improving its mechanical design. Therefore, we developed the design of the scaled robot to eliminate static behavior. The dynamic model was established and the electronic architecture was described. Besides, the control scheme was proposed. In conclusion, our study demonstrates the importance of the mechanical symmetry design and the control law to ensure the stability of the underwater robot.