Dexterous Task-Priority Based Redundancy Resolution for Underwater Manipulator Systems

The problem of redundancy resolution for underwater remote vehicle-manipulator systems (URVM) is addressed in the current work. In URVM applications, it is beneficial to have the underwater remote vehicle (URV) hold station using its thrusters while a human pilot operates the serial manipulator. This provides a stable platform for the manipulator and eases the pilot’s job drastically when current and/or tether disturbances are present. However, when following this objective, the redundancy of the URVM as a whole is wasted; the four actively controlled motions of the URV are not used to improve the efficacy of the manipulator task. In fact, this standard operating procedure frequently puts the manipulator into near singular configurations. This is not desirable from the manipulator controller standpoint since near singular configurations result in undesirably high joint velocities and oscillations. In this work, a new heuristic approach based on the task-priority redundancy resolution scheme is applied to the URVM. The proposed approach provides a means to avoid singular configurations of the manipulator, and provides dexterous manipulation by using the URV’s mobility in an optimal, coordinated manner. This scheme is particularly useful for remote systems where an a priori trajectory generator is not applicable. Numerical case studies are developed to demonstrate the effectiveness of the technique.