As the unmanned surface vehicle acquires the location information of the underwater remotely operated vehicle(ROV) through GPS and USBL, it can gather real-time underwater information of the ROV currently being explored. For this, a combined surface vehicle and unmanned underwater vehicle has been studied that has the advantage of supplying power to the ROV and receiving large quantities of underwater information in real time. The combined system consists of an surface ship, the ROV and a winch system that controls the depth of the ROV. For the surface ship, it is possible to maintain the current position by using GPS and to track the pre-designed target route automatically or manually through communication with the land and the mother ship. The winch system controls the depth of the underwater ROV for each location. The ROV is controlled to locate at a certain position in the water or to synchronize with the path of the ship by identifying the relative position of the ship through the ultra sonic base lin(USBL) sensor.
In order to perform such a task, the propulsion of each axis of the underwater ROV must exhibit control performance to overcome the interference caused by the disturbances such as the tidal current occurring in the water and maintain the attitude. USV is connected the ROV using winch cables and receive relative positioning errors with respect to the USV in real time through USBL mounted on each hul. In addition, the depth of the water is controlled by the winch system installed on the USV.
In this reason, DP (Dynamic Position) control of underwater ROV is essential. The ROV which is located at the relative position of the USV and is synchronized with the motion of the USV may cause motion disturbances due to underwater disturbance such as currents around the ROV. In particular, it is very difficult to maintain a constant position under the influence of underwater currents generated in all directions underwater. In order to solve this problem, the flow characteristics around the ROV generated by the hull attitude of the ROV are investigated, and the posture angles of the ROV that can maintain a more efficient and stable influence of the flows are systematically investigated.
To do this, two types of underwater ROV hull models are developed, and perform modelling them through 3D CAD, and then apply the generated hull modeling data to computational fluid dynamics (CFD). In addition, to verify the CFD results, the linearization and hull angle visualization test methods are performed in parallel.