Redundancy resolution for underwater vehicle-manipulator systems with minimizing restoring moments

In this paper, redundancy resolution of underwater vehicle-manipulator system(UVMS) is addressed. In general, UVMS has redundant degrees of freedom(DOFs) as many as DOFs of manipulator and these redundant DOFs can be used to optimize the configuration of UVMS while satisfying given tasks. We propose a performance index for redundancy resolution which minimizes the restoring moments of UVMS. The restoring moment is induced from gravity and buoyancy forces and it can cause unintentional change of poses of UVMS. If the restoring moments remain small, control effort for keeping the poses of UVMS decreases. This means that energy consumption can be reduced by minimizing the restoring moments during conducting tasks. We solve inverse kinematics of UVMS using well-known weighted pseudo-inverse matrixes and we optimize the restoring moments by adopting gradient projection method. Numerical simulations are presented to demonstrate performance of the proposed algorithm.