Structure And Impedance Control Of Three DOF Underwater Manipulator

With the acceleration of the ocean development, the demand of underwater operations equipment is increasing. The underwater manipulator is an important tool while operating in water. And it has played more and more important roles in areas of underwater exploration, underwater mining and offshore oil engineering etc. At the same time, there are many special problems need to be studied and resolved for the architecture and control technology of underwater manipulator which compared with the land-based manipulator because of the special underwater environment. A 3-DOF experimental prototype of underwater manipulator is developed which take the manipulator of ROV as research object. Aiming at the problem of impedance control for underwater manipulator, the researches of theories and experiments are carried out.The general scheme of 3-DOF underwater manipulator is presented according to the requirement of the working environment, operating content and performance of underwater manipulator on the basis of analyzing the present state of study for the architecture and control technology of underwater manipulator. And the prosthetic structure is determined including body structure, transmission system, seal and gripper mechanism. The structure form of each joint and the range of angle are determined. The body structure and control system are designed and the installation and debugging are completed for body structure and control system of underwater manipulator.The kinematics model of 3-DOF underwater manipulator is built, the problem of inverse kinematics of manipulator is researched, the Jacobian matrix of manipulator is introduced, and the dynamic equation of the underwater environment is built by the equation of Lagrange and the computer simulation is made. The influence of resistance coefficient between the land-based and underwater environment to the movement of underwater manipulator is analyzed. And the working space of manipulator is analyzed by the static analytical method.The force-position control of underwater manipulator is the hot spot of the current research. The impedance control algorithm based on position under the unknown environment is presented, and the computer simulation is made under multi-constraints conditions. The simulations results show that the adjustment and optimization of the impedance control parameters can reduce the impact force when the manipulator contact with the effective object. And the regulation of the impedance control parameters is researched and summarized.The principle prototype of underwater manipulator is completed. The more complete experimental system of land-based and pool-based is built. The experimental researches of the joints characteristic, position control and force control for underwater manipulator are made, and the joint control regulation is summarized under the different depths environment. The experiments of force tracking control and restrained plan control are made based on underwater restrained environment. The experimental results show that the control strategy and the control method of underwater manipulator which presented in this paper are effective and feasible.