Impedance control based on error feedback for the manipulator of an underwater vehicle-manipulator system

This paper deals with the design of a motion and force control scheme for underwater vehicles, each of which has a manipulator. For a subsea operation that requires a contact between the manipulator’s tip (e.g., the hand) and various types of environments, it is desirable that the mechanical impedance of the manipulator is adjusted according to the contact surface. From this point of view, the paper focuses on the design of an impedance control scheme. Several impedance controllers have been developed. Most of them were designed on the assumption that the control capability of the vehicle is the same as that of the manipulator. However, it has been pointed out in the literature that for a real underwater robot, its vehicle control is more challenging than its manipulator control, because the vehicle has much larger inertia, and many more inaccurate position sensors and actuators than the manipulator. In view of this fact, we develop an impedance control scheme for the manipulator under the condition that the vehicle is independently controlled by a motion controller with poor performance. Moreover, we provide the results of simulations for comparing an existing controller with the proposed one.