Structure design and workspace calculation of 6-DOF underwater manipulator

This paper describes the structure design of a 6-DOF (Degree of Freedom) underwater robotic manipulator arm and the analysis of its workspace. Robotic arm very closely resemble human hand and its design is based on the principle of human hand. The structure of the manipulator arm consists of shoulder, elbow and wrist. The robotic manipulator arm works underwater more safely and for longer time as it does not breathe like human. The arm is designed for underwater applications of pick and place, inspection and welding and other related work. The manipulator is 6-DOF serial robotic arm, like other common industrial robotic manipulator. It has 6 joints, which are all of revolute type. The manipulator structure is designed such that all links are connected in series by DC motor-actuated joints from base to an end-effector. The material of the links and joint shell is selected water resistant and all the joints are made waterproof by using both static and dynamic sealing. The motors and reducers are selected for each joint on the basis of static moment balance approach. The structure of the manipulator arm is modeled in pro-e modeling software. The workspace of the manipulator is calculated using both the MATLAB Robotics toolbox and graphical method. The toolbox gives the 3-D workspace while the graphical method gives the 2-D workspace in horizontal and vertical plane.