HYBRID POSITION FORCE CONTROL OF A HYDRAULIC UNDERWATER MANIPULATOR/

Current generation underwater remotely operated vehicles equipped with robotic manipulators are teleoperated and consequently place a large workload burden on the human operator. A greater degree of automation could improve the efficiency and accuracy with which underwater tasks are carried out. A hybrid position/force control scheme is proposed to control an industrial hydraulic underwater manipulator, modified to i nclude a force/torque sensor, for tasks such as weld inspection. Model ling of the hydraulic actuation mechanism is performed and the resulti ng model is easily incorporated in the standard robot dynamic equation s. An experimental facility using a PC-based digital signal processor is used to produce practical hybrid position/force results for Slingsb y TA9 hydraulic arm. Results are presented for the manipulator sliding across a planar surface in different parts of its work envelope. Good general agreement is obtained between the simulated and practical sys tems. A fixed gain control strategy is shown to work well, provided it is tuned for the arm configuration when sliding occurs.