6. Kinematic Control of UVMSs

Abstract

A robotic system is kinematically redundant when it possesses more degrees of freedom than those required to execute a given task. A generic manipulation task is usually given in terms of position/orientation trajectories for the end effector. In this sense, an Underwater Vehicle-Manipulator System is always kinematically redundant due to the DOFs provided by the vehicle itself. However, it is not always efficient to use vehicle thrusters to move the manipulator end effector because of the difficulty of controlling the vehicle in hovering. Moreover, due to the different inertia between vehicle and manipulator, movement of the latter is energetically more efficient. On the other hand, reconfiguration of the whole system is required when the manipulator is working at the boundaries of its workspace or close to a kinematic singularity; motion of the sole manipulator, thus, is not always possible or efficient. Also, offline trajectory planning is not always possible in unstructured environments as in case of underwater autonomous missions.