Virtual Kinematic Chains to Solve the Underwater Vehicle - Manipulator Systems Redundancy

This paper addresses the kinematics of the Underwater Vehicle-Manipulator Systems (UVMSs). Due the adittional degrees of freedom (dofs) provided by the vehicle, such systems are kinematically redundant, i.e. they possess more dofs than those required to execute a given task, and need to be solved using some redundancy technique. We present an approach based on introducing kinematic constraints. The approach uses the screw representation of movement and is based on the so-called Davies method used to solve the kinematics of closed kinematic chains. We describe the vehicle-manipulator system as an open-loop chain and present a virtual kinematic chain concept that allows closing this open chain. Applying the Davies method to this resulting closed chain, the UVMS direct kinematic is solved. The inverse kinematics is obtained using the same approach, by introducing extra constraints derived from energy savings requirements. The proposed approach is compared to another redundancy resolution method to illustrate the ability of the proposed strategy.