To Örebro University

Biofouling build-up on submerged structures such as ships, petroleum and gas storage tanks, electric power plants, bridges, oil rigs etc. is a major problem that affects the surface material of the structure, the eventual hydrodynamic quality of the surface and in some cases the efficacy of cooling systems. Underwater cleaning is a solution to maintain submerged structures in order to assure proper functioning for as long as possible. Consequently, there has been an increased interest in the development of new technologies for robotised underwater cleaning systems.

This thesis presents a new concept of a flexible crawling mechanism for an industrial underwater cleaning robot, which is evaluated from the viewpoint of its capability to work underwater, scanning the desired surface, and perform a cleaning task. The main research questions investigated in this thesis are: (1.) how to select the most important features in choosing the platform mechanism to fulfil the surface scanning operation, (2.) how to design the platform in order to bear the forces related to the cleaning task, (3.) how to maintain surface contact throughout cleaning, (4.) determine the significant parameters to be monitored in order to ensure stable positioning on the surface during the cleaning process and (5.) how to develop the control of actuators to realise the locomotion and to follow the desired trajectory.

This thesis begins with a classification and discussion of the available solutions for underwater operation, taking into consideration the benefits and drawbacks, overall efficiency and environmental and human safety issues. From this survey, an underwater mobile robotic platform is designed to address the main requirements and industrial needs. Further, a study and simulation of its mobility and stability on the surface is performed and a complete scenario of the entire cleaning operation is presented. In addition, an overview of the required sensors and the control system is given. Finally, a new robotised system was developed to clean underwater surfaces with minimum active degrees of freedom. A successful simulation and real experimental results were obtained with a simplified lab-scale prototype. The thesis concludes with a summary of future works and outlook for the growing field of underwater cleaning robots.