Study of manipulator operations maneuvered by a ROV in virtual environments

It is extremely difficult to operate an underwater manipulator carried on a remotely operated vehicle (ROV) in the deep sea. In order to investigate underwater manipulator operations maneuvered by a remotely operated vehicle (ROV), this paper develops a virtual underwater manipulator and its carrier, the ROV, via the three-dimensional simulator “Webots” to animate operational tasks. The ROV model refers to the structure of a typical ROV which operates below the ocean's surface down to 1000 m, while the graphical and kinematic models of the manipulator refer to a master-slave servo hydraulic manipulator with 7 functions, consisting of six degrees of freedom (DOFs) and a parallel gripper for manipulations. This study uses the virtual platform to challenge an operator to conduct different tasks by using the manipulator, including two switch-based and one master arm-based operation, and combined by remote and autonomous operations. When conducting the operations, we have considered uncertain external disturbances that stem from subsea environments. In order to demonstrate the feasibility and effectiveness of the virtual platform, we have designed two typical underwater operational tasks for training the operator: grasping a machine part in a basket, and making a circle at a specified position on the seabed. The tasks are completed by coordinating the underwater manipulator, the submersible vehicle, and a pan-tilt camera. Three operators were invited for the training operations, and their operating results are presented.