Dynamic buoyancy control of an ROV using a variable ballast tank

Remote operated vehicles are tethered marine robots that are widely used in industry and science. Underwater vehicles such as ROVs operate while tethered to a surface ship, and must be able to surface and submerge, thus requiring dynamic buoyancy control. Our ROV "JAWS" incorporates a variable ballast tank that has been scaled down and adapted to a small, highly maneuverable vehicle. In order to compete in the Marine Advanced Technology Education (MATE) Center ROV Competition, open class, the ROV that we have designed and built must locate, recover, and retrieve the ROV "RUSTI" within a time limit, then surface with RUSTI while remaining stable in pitch, roll, and yaw. Our ROV requires dynamic buoyancy control for its own stability and depth control, and to compensate for an additional ten pounds of negative buoyancy from RUSTI. The variable ballast tank is welded aluminum, customized for the competition challenge. All sensors, electronics, and computing necessary for dynamic buoyancy control have been designed and implemented specifically for our ROV and its mission. Our ROV design is modular, for easy assembly and disassembly, and built primarily from off-the shelf components, for easy replacement and competitive cost. The ROV is small and highly maneuverable with powerful motors and sophisticated controls.