Tool-Point Control for a Redundant Heave Compensated Hydraulic Manipulator

In this paper, theoretical and experimental implementation of heave compensation on a redundant hydraulically actuated manipulator with 3-dof has been carried out. The redundancy is solved using the pseudo-inverse Jacobian method. Techniques for minimizing velocities and avoiding mechanical joint saturations is implemented in the null space joint motion. Model based feed-forward, combined with a PI-controller handles the velocity control of each joint. A time domain simulation model has been developed, experimentally verified, and used for controller parameter tuning. Model verification and experimental results are obtained while the manipulator is exposed to wave disturbances created in a dry environment by means of a Stewart platform.