Design and climbing control of an underwater robot for ship hull cleaning

Underwater robot has significant potential to clean the fouling on the ship hull. The design of robotic solution as well as control scheme is, however, still challenging. The use of negative pressure and magnetic adsorption technologies in cleaning robots will severely limit their utility in rough hulls and warships. Here we propose an underwater cleaning robot that driven by six thrusters and two crawler belts. The key advantage of our robot is that thrusters can provide enough and reliable adhesive forces to adapt to more common hulls. Furthermore, we present a climbing controller to track the planned coverage path that can guide the robot covering the ship hull without repetition and omission. The difficulties lie in two aspects: inconsistency between two crawler belts and inaccurate depth measurement that caused by changing wave near the water surface. Here we use velocities of crawler belts and pitch angle of the robot to replace the inaccurate depth measurement, and then design a consensus-based sliding mode controller to relieve the inherent inconsistency for tracking the coverage path accurately. Finally, field experimental results on giant ship verify the effectiveness of the presented robotic solution and controller.