| Underwater manipulator is an important tool in ocean development. In order to thoroughly understand its dynamic character, increase the accuracy of the servo control, enhance its work ability and reduce its dependence on operators. Joint drivers, hydrodynamics, servo control and autonomous manipulation which are closely linked with underwater manipulation are studied. The main contents are given below.At first, the dynamic of underwater electric manipulator joint is analyzed. Oil filled motor is our research object. Through theoretical calculation, the oil friction torque is calculated. A dynamic model of oil filled motor is established. The relation between oil friction and water pressure is studied. Through experiments, one joint motor's efficiency in different pressure is tested. Choosing appropriate oil and polishing joint inner space are two methods for increasing the joint's efficiency.Then, the hydrodynamics of underwater manipulator are studied.The hydraulic forces are decomposed into two parts, one is in still water and the other is in sea current. Based on the Morison equation and the Lagrange method, an underwater manipulator dynamic model when flow exists is established. Through numerical calculation, the contribution of hydraulic resistance, buoyancy, sea steady flows and unsteady flows to manipulator's dynamic are studied. It is found that the value of joint torque caused by the buoyancy and the gravity are in the same order of magnitude. The comparison of the hydrodynamics torque caused by flow and motion of manipulator depends on the speed of flow and manipulator motion.After that, the manipulator control based on dynamic model is studied. As the high accurate servo control of underwater manipulator under variation load is difficult, the slide mode control is applied in the manipulator servo control. The design of the controller is presented in detail. In the controller, the dynamic model is used, but it doesn't need the accurate mathematic model. Numeric simulation and experiment results demonstrate that it has self adaptability to variation load.At last, as operation of manipulator is a tedious work and the accuracy is hardly achieved, the autonomous manipulation is studied to reduce manipulator's dependence on operators. An underwater 3500m electric manipulator (named huahai-4E, stands for four functions deep ocean electric manipulator in China) is used as a test bed. It is equipped with a unique ultra-sonic probe array and an underwater camera. Vision has been adopted in recognition of the target which is a cylinder with black squares in surface. The ultra-sonic sensor is used for obtaining the distance and approximate location of the target. After nonlinear correction, vision is used for obtaining the location angle error of the target. Both of vision and ultra-sonic sensor are used in autonomous grasping. A four step grasp algorithm is discussed in details. It is successfully used in the underwater autonomous manipulation.
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