Abstract. Manipulator is of vital importance to the remotely operated vehicle (ROV), especially when it works in the nuclear reactor pool. Two degrees of freedom (2-DOF) underwater manipulator is designed to the ROV, which is composed of control cabinet, buoyancy module, propellers, depth gauge, sonar, a monocular camera and other attitude sensors. The manipulator can be used to salvage small parts like bolts and nuts to accelerate the progress of the overhaul. It can move in the vertical direction alone through the control of the second joint, and can grab object using its unique designed gripper. A monocular vision based localization algorithm is applied to help the manipulator work independently and intelligently. Eventually, field experiment is conducted in the swimming pool to verify the effectiveness of the manipulator and the monocular vision based algorithm. Keywords: ROV, 2-DOF manipulator, monocular camera, monocular vision segmentation algorithm
IntroductionThese guidelines, Underwater research and development has becoming faster and faster during the last decade. However, the extreme conditions such as high water pressure, invisibility and non-oxygen become great barriers for human to access directly [1]. Underwater robots are expected and developed as efficient tools for the operation instead of human beings, and ROV is just one of them. Based on this, the manipulator mounted on the ROV is expected to play an important role for complex tasks, such as grabbing small parts like bolts and nuts in the nuclear reactor pool.There are many manipulators that are developed for industrial purpose but fewer for underwater utility on account of the high sealing requirement in the highpressure underwater environment and complex control method. A visual servoing control system was proposed for a two-link electrically actuated underwater manipulator by Maruthupandi A etc, and its effectiveness had been verified in a laboratory water tank using visual feedback to process the position and tracking control of the 2-link underwater robot manipulator [2]. CC Chang et al. [3] had designed and implemented an intelligent underwater robotic manipulator system, which consisted of a manipulator, ad distance measurement system, water-proof camera, computer, interface technology and task planning technology etc, to enhance the capability of the robotic manipulator to fulfill the need of less-skilled or even non-skilled operators. It has five rotary joints, including waist, shoulder, and elbow, wrist-pitch, and wrist-roll motion, and can accomplish an object grab under water with an ROV system. The 2-DOF manipulator designed and manufactured by us is mounted on an ROV that is used to inspect the reactor pressure vessel and other water-filled infrastructure in the nuclear reactor pool. It has two joints, and can move in the vertical direction alone through the control of the second joint and grab object using its unique designed gripper. A monocular vision based localization algorithm is applied to help the manipulator grab obje...