Design of an Environmentally Responsive Grooming Tool to Aid in Underwater Navigation

Abstract

Underwater hull grooming is a proactive approach to ship hull husbandry. It has been defined as the frequent and gentle wiping of a ship hull coating to maintain it free of fouling. One of the challenges to implementing a grooming schedule is the control and navigation of the devices over the surface of the hull. This thesis presents prior research that has developed self-attaching rotating brushes as an effective method to groom fouling control coatings and the results from several years of implementation in the marine environment. The hypothesis of this thesis is that the condition of the ship hull surface can be interpreted by monitoring the current draw of the grooming tool and that this information can be used to aid in navigation. The present grooming tool design comprises five self-attaching rotating brushes that maintain constant RPM by regulating current through a control system which monitors the back EMF of a brushless DC motor. Experiments were performed to investigate the relationship between current draw and surface condition by operating the grooming tool on artificial roughness’s and fouling control coatings with known levels of biofouling. The results demonstrated that coating type, coating roughness and biofouling type all contributed to the current draw by the brush motor. This knowledge may be used to help locate the grooming device when operating in a lawn mower type pattern.